heather.txt

// 
// Lady Heather's GPS Disciplined Oscillator Control Program
// (now works with many different receiver types and even without a GPS
//  receiver.  Also works with precision rubidium/cesium oscillators and
//  frequency / time interval counters).
//
// Copyright (C) 2008-2019 Mark S. Sims
//
//
// Lady Heather is a monitoring and control program for GPS receivers, GPS
// Disciplined Oscillators, precision oscillators (rubidium and cesiem), and
// frequency / time interval counters.  Heather is oriented more towards the 
// time keeping functionality of GPS and less towards positioning. It supports
// numerous GPS (and Glonass, Beidou, Galileo, etc) devices including:
//
//      GPS Receivers:
//         Ashtech Z12 receiver
//         Furuno GT-8031 (uses $PFEC commands)
//         Furuno GT-87xx (using eSIP commands)
//         GPSD interface (mainly a Linux/macOS/FreeBSD thing - GPSD provides
//              a shared read-only interface to numerous GPS devices.
//         Jupiter-T  (aka Zodiac)
//         Motorola binary 
//         NMEA
//         NVS BINR binary (115200:8:N:1)
//         Sirf binary
//         Trimble TSIP binary receivers
//         Trimble TAIP receivers
//         Trimble SV6/SV8/ACE-III
//         Trimble Accutime / Palisade receivers
//         Trimble RT17 format receivers (like the NetRS)
//         TymServe 2000 (not yet tested)
//         Ublox UBX binary 
//         Venus/Navspark (115200:8:N:1)
//
//      GPSDO's (GPS disciplined oscillators):
//         Brandywine GPS-4 receiver
//         DATUM STARLOC II GPSDO - inferior wannabe Thunderbolt
//         Jackson Labs LTE Lite
//         Lars simple GPSDO controller (used with any 1PPS output GPS receiver)
//         Lucent RFTG-m GPSDO
//         Lucent KS24361 REF0/Z3811A  Z3812A
//         NEC GPSDO ... STAR-4 compatible at 115,200 baud
//         Oscilloquartz STAR-4 GPSDO (management interface)
//         Oscilloquartz OSA-453x GPSDO
//         SCPI - Nortel telecom GPSDOs like NTWB and NTPX in SCPI mode
//         SCPI (Z3801A/Z38015/Z3816/etc style)
//         SCPI (HP5xxxx style)
//         Spectrum TM4  (not fully tested)
//         Trimble TSIP binary GPSDOs (like the Thunderbolt and numerous 
//           "telecom" GPSDOs.
//         TruePosition GPS
//         UCCM - small Trimble / Symmetricom / Samsung telecom GPSDOs 
//           (57600 baud)
//         Zyfer Nanosync 380 (19200:8:N:1)
//
//     Atomic frequency references:
//        HP 5071A cesium beam oscillator
//        Spectratime/Temex LPFRS rubidium 
//        Spectratime/Temex RMO rubidium  (same as LPFRS)
//        Spectratime SRO100/SRO70 rubidium 
//        SRS PRS-10 rubidium oscillator
//        Symmetricom SA22 rubidium (60 Mhz and 58.9824 MHz ref freq)
//        Symmetricom X72 rubidium
//        Symmetricom X99 rubidium
//
//     Clocks:
//        Acron Zeit WWVB receiver
//        Gravity/solid earth tide clock (uses system clock to display 
//          solid earth tides and gravity offset,  Requires manual entry
//          of latitude/longitude/altitude)
//        No receiver, uses system clock. 
//
//     Time and frequency counters:
//        Generic frequency/time interval counters
//        HP531xx counters
//        Lars simple GPSDO controller
//        PICPET simple timestamping interval counter chip
//        TAPR TICC time interval counter
//
//     Misc:
//        Simple terminal emulator
//        RPN calculator
//
//
// Permission is hereby granted, free of charge, to any person obtaining 
// a copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation 
// the rights to use, copy, modify, merge, publish, distribute, sublicense, 
// and/or sell copies of the Software, and to permit persons to whom the 
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included 
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.
//
//
// Original Win32 port by John Miles, KE5FX (john@miles.io)
// Help with Mac OS X port by Jeff Dionne and Jay Grizzard
//   (note: OS/X version uses the XQuartz package for X11 display support)
// FreeBSD support by Daniel Lawrence
//
// Temperature and oscillator control algorithms by Warren Sarkison
//
// Original adev code adapted from Tom Van Baak's adev1.c and adev3.c
// Incremental adev code based upon John Miles' TI.CPP
//
// uGal gravity calculation code slightly adapted from Tom Van Baak's 
// tides.c which was derived from code by J.L. Ahern which was based upon 
// equations by P. Schureman
//
// Solid earth tide code translated from Fortran solid.f using the F2C 
// translator program.  solid.f was written by Dennis Milbert and is based 
// upon the dehandtideinel/MJD code by V. Dehandt,  S. Matherws,  J. Gipson,
// and C. Bruynix.
// 
// Easter and moon illumination phase code from voidware.com
//
// moon_info() derived from code in John Walker's moontool.c
//
// Equation of time code adapted from code by Mike Chirico and NOAA
//
// Sun position code is Grena's Algorithm 5
//
// Moon position from code by Paul Schlyter at
//   http://hotel04.ausys.se/pausch/comp/ppcomp.html
//
// Heliocentric Julian Date code adapted from code by Richard Ogley.
//
// Nutation and obliquity code derived from code by Jay Tanner and JPL
//
// Equinox/Solstice equations derived from Jan Meeus "Astronomical Algorithms"
//    via Simon Cassidy.
//
// Time of perihelion derived from table by Fred Espenak, www.Astropixels.com
//
// New moon table derived from table by Fred Espenak, www.Astropixels.com
//
// Moon image code derived from code by Mostafa Kaisoun.
//
// Nortel NTGS55A recever wakeup research by Sam Sergi
//
// Linux IPv6 support by Kasper Pedersen
//
// The LZW .GIF encoder used in this program was derived from code written by 
// Gershon Elber and Eric S. Raymond as part of the GifLib package.  And by 
// Lachlan Patrick as part of the GraphApp cross-platform graphics library.
//
// Singing clock excerpted from Palistrina, Missa Assumpta by the Tallis
// Scholars...  you should buy some of their stuff... they are quite good.
//
//
//
// This file contains most of the operating system dependent routines, 
// initialization routines,  serial port I/O,  and the screen I/O and 
// plotting routines.
//
//
//
//
//
//
//
//-PROGRAM CONFIGURATION AND HELP INFORMATION
//
//   Heather has two types of user commands.  The first is the command line
//   options.  You can get a list of command line options by starting Heather
//   with an invalid command line option such as "/?".  This will bring up
//   a scroll box of commands on Windows and several pages of commands on
//   other operating systems.  You can also enter "?" from the keyboard to
//   bring up the command line help information.  
//
//   Command line options can begin with either a '/' (Windows standard) 
//   or a '-' (Linux / macOS standard).  Either is acceptable no matter what
//   operating system you are using.  Options must be separated by a space.
//   Note that file names may not contain spaces and quoted options are not
//   supported!
//
//   Once Heather has started, you can enter command line options from the 
//   keyboard using the "/"  keyboard command.  There are a few command line 
//   options that cannot be changed from the keyboard once Heather has started.
//
//
//
//   The second set of commands are the keyboard commands. You can get a list
//   of the primary keyboard commands and menus by pressing SPACE.  Note that
//   not all receivers support all of the keyboard commands.  Keyboard menu
//   commands are shown in this documentation in upper case characters, but 
//   either upper case or lower case are acceptable.
//
//   Pressing the first key of a command menu will show a sub-menu of commands
//   available under that menu.  Pressing the second key of a menu command
//   will either execute the command or, more commonly, prompt for a value
//   to enter.  The default value offered as the input is either the current
//   setting or a common value to use.  You can press ENTER to accept the 
//   offered value, ESC or ESC ESC to abort the command, enter a new value, 
//   or edit the offered value.
//
//   LEFT and RIGHT arrows move the cursor within the string. INSERT
//   toggles insert mode.  HOME moves to the start of the string.  END moves 
//   to the end of the string.  DEL deletes the character at the cursor.
//   DOWN arrow deletes to the end of the line.  UP arrow deletes to the
//   start of the line. BACKSPACE deletes the character before the cursor.
//   PAGE_UP retreives the last command entered. This lets you repeat the
//   last entered command value or recover from a botched line edit.
//
//   If a keyboard command suggests an input value and the first character 
//   that you enter is a not an  editing character,  the offered value is 
//   erased so that you don't have to backspace over it to enter a new value.
//
//
//
//   Heather's configuration comes from three places:
//
//      First is a hard coded configuration in the program.
//      Next is from the file "heather.cfg"
//      Finally is from the command line that starts the program.
//  
//   The location of "heather.cfg" depends upon the operating system and how
//   Heather was started (from a command line or from a desktop icon).  You
//   can determine where to place the file by bringing up the command line
//   help information (described above) and scrolling down to the bottom of
//   the help information.  There will be a line that says:
//     "Put heather.cfg file in directory ..."
//   The location of the file is also shown (in GREEN) when you press SPACE
//   to get the keyboard help menu.
//
//   Note that if you rename the "heather" executable file,  the .cfg and .cal 
//   file names that Heather uses will also change to match the new executable
//   file name.
//
//   Note that this directory is also the default directory that Heather uses
//   for all of its support files (sound files, log files, screen dumps, etc).
//
//   If you launch Heather from a WINDOWS desktop icon, you can set the command
//   line options by right clicking on the icon and selecting PROPERTIES. 
//   The TARGET field will show the command command line to use.
//
//   Note that in this file a lot of command line options are described as
//   "toggle" options.  Toggle options are like on/off switches.  For instance:
//      /gw  - will toggle the watch display between on and off and back on 
//             each time it is seen.
//
//   You can override this toggle action and explictly set the state.
//   For instance:
//      /gw0 - forces the watch display OFF
//      /gw1 - forces the watch display ON
//
//
//
//   LADY HEATHER'S CONFIGURATION FILE "heather.cfg" :
//
//   Place the command line options that you want to use in this file
//   with one command line option per line.  Each option MUST start in column
//   one with a '/', '-', '@', or '$' otherwise the line will be treated as 
//   a comment.
//
//   Lines that begin with '/' or '-' set command line option values.
//
//   Lines that begin with '$' send hex values to the receiver.
//
//   Lines that begin with '@' send keyboard commands (all '@' lines are copied
//   to temporary keyboard script file "heathtmp.scr" which is then processed 
//   once Heather has finished initializing the hardware, etc).  See the
//   description of keyboard script files below.
//
//   You can also read in a ".cfg" file from the keyboard "R" menu or from
//   the command line:
//      /r=file.cfg  - reads a .cfg configuration file. These config files are
//                     processed after the default "heather.cfg" file has been
//                     processed.  You should not include a "/r=file.cfg"
//                     command in a .cfg file since reading config files do 
//                     not nest!
//      Note: earlier versions of Lady Heather used the /h command to read
//      .cfg files.   The /h command now displays command line help.
//
//
//   At a minimum, most users will want to configure the com port, receiver
//   type, and time zone in their default configuration.
//
//   If an error is detected in a command line option in the .cfg file, 
//   processing of the file is stopped and the command line help screen is
//   shown.  The offending option is listed at the end of the help info.
//
//
//
//   KEYBOARD SCRIPT FILES:
//
//      Lady Heather has the ability to read keyboard script files.  These
//      file must have an extension of ".scr"  Script files mimic typing
//      from the keyboard.  Script file names must be less than 128 characters
//      long.
//
//      Commands that would normally suggest an input do not 
//      do it when read from a script file.  They behave
//      like you first entered ESC to erase the suggestion.  
//
//      Commands that normally toggle a flag may be followed 
//      by a "1" or "0" to set the flag value directly. e.g.
//      you can use GW0 in a script file to force the watch display
//      OFF. A few commands (like GS) do not toggle a specific value
//      and cannot be used this way.
//
//      You can put more than one command on a line (separated
//      by spaces) until you do a command that expects a
//      parameter value or string.  
//
//      A '~' in a script file pauses reading from the script 
//      and starts reading from the keyboard until a carriage
//      return is seen.  This is useful for entering a parameter
//      value or string.  e.g.  GG~ will pause the script and
//      prompt for a graph title.
//
//      Any text following a ';' or a '#' in a script file 
//      is a comment and is ignored.
//
//      Script files abort upon the first error detected or any 
//      unrecognized command is seen.  
//
//      Script files can be nested up to 5 levels deep.
//      Scripts can be stopped by pressing any key.
//
//      You can cause processing of a keyboard script file to wait for a
//      time interval or a specific time.  See the section on ALARMS for
//      a description of how to do this.
//
//      To run a script file use the "R" keyboard command or "/r" command
//      line option and specify a file name with an extension of ".scr"
//
//      The function keys F1..F10 (F1..F9 on Windows) cause keyboard script 
//      files "f1.scr" to "f10.scr" to be read.  This allows F1..F10 to be
//      used as programmable function keys.
//
//      Heather normally puts a short pause between each character read from
//      a script file.  You can toggle "fast script" mode with the /nf command
//      line option.
//
//      
//
//
//
//-CONFIGURING THE COM PORT:
//
//   Lady Heather talks to the GPS device via a serial port (hardware or USB)
//   or an internet TCP/IP connection.  You need to tell Heather which 
//   communications device to use.  For serial ports you use the "/#" command
//   line option (where # is the com port number to use):
//      /1 says to use COM1
//      /2 says to use COM2, etc
//      /0 says to not use a communications link.  This can be useful if you
//         are just reading a log file, etc and do not want to talk to a receiver.
//
//   On Linux systems the # number you specify IS 1 MORE THAN THE SERIAL PORT
//   NUMBER:
//      /1 says to use /dev/ttyS0 on Linux
//      /1 says to use /dev/ttys0 on macOS
//      /1 says to use /dev/cuaU0 on FreeBSD
//
//      /2 says to use /dev/ttyS1 on Linux
//      /2 says to use /dev/ttys1 on macOS
//      /2 says to use /dev/cuaU1 on FreeBSD
//
//      /999 says to use /dev/heather
//
//   Windows treats USB connected serial adapters as standard hardware serial
//   ports.  Most Linux and macOS users will be using USB serial converters.
//   These operating systems treat the USB devices differently than hardware
//   serial ports.  For these system you can use the "/#u" command line option.
//       
//      /1u says to use /dev/ttyUSB0 on Linux systems and
//      /1u says to use /dec/tty.usbserial on macOS.
//      /1u says to use /dev/cuaU0 on FreeBSD
//
//      /2u says to use /dev/ttyUSB1 on Linux systems and
//      /2u says to use /dec/tty.usbserial1 on macOS.
//      /2u says to use /dev/cuaU1 on FreeBSD
//     
//    You can also follow the com port number with an "a" to use a /dev/ttyACM
//    device:
//      /1a says to use /dev/tty/ACM0
//      /2a says to use /dev/tty/ACM1  ,etc.
//
//   If your system does not use these standard device names, you can specify 
//   the input device name to use with the "/id=" command line option:
//      /id=/dev/your_device_name
//
//   Heather also supports using a TCP/IP connection to talk to your receiver.
//      /ip=addr:port
//      addr can be be either a numeric address like 192.168.10.20 or a web
//      address like ke5fx.dyndns.org   
//
//      If the :port number is not given Heather uses port 45000
//
//   Note that if the specified IP address is not valid or cannot be reached
//   Heather may appear to hang for quite a while until/if the connection 
//   attempt times out.  This is particularly true for numeric IP addresses.
//
//   On Linux and macOS Heather supports IPv6 addresses. If the specified
//   IP address is a "bracketed" IP address [....] you can specify the port
//   number to use like [....]:45000  otherwise you can force an IPv6
//   connection by using a ';' before the port number.
//
//
//   For hardware serial port and USB serial connections you can specify the
//   serial port baud rate and data format with the "/br=" command line option:
//      /br=9600:8:N:1   (9600 baud, 8 data bits, no parity, 1 stop bit)
//      /br=19200:7:E:1  (19200 baud, 7 data bits even parity, one stop bit)
//      /br=57600:8:O:2  (57600 baud, 8 data bits odd parity, two stop bits) 
//
//   Many receivers that connect via a native USB port (not a USB-serial
//   converter cable) use a "CDC" driver that effectively ignores the baud
//   rate, etc parameters.  You can Heather's port config to anything and
//   they will still work.
//
//   There is another parameter (:Px) that you can add to the /br parameters 
//   to select which external device (see the following section on external
//   devices for more information) that you want to configure.
//
//   If a baud rate parameter is not given in the "/br=" string, that
//   parameter is not changed.  Previous versions of Heather set that 
//   parameter to a default value.
//
//   If a baud rate command is not given, Heather will use a default value
//   that is most commonly used for the receiver type it is using... which
//   may not be the same as what your receiver is configured for!
//
//   Another way to specify the baud rate is to follow the serial port number
//   with an ',' and the baud rate info like:
//       /1,9600:8:N:1
//
//
//   If com data is lost or the com port disappears Heather will attempt to
//   re-init the com port every "com_timeout" interval (5-25 seconds 
//   depending upon the receiver type and the operation being done). 
//   You can disable com port error recovery with the /ce command line option.
//   Heather can recover from things like yanked ethernet cables and USB 
//   dongles and dropped WIFI connections.
//
//   You can specify the com port data loss timeout (in milliseconds) with 
//   the "/ct=#" or "/ct?=#" command line option.  /ct sets the timeout for
//   all devices ports.  /ct? sets the timeout for just port '?' where '?'
//   is the port identifier for the port.  See the section below on the
//   external/extra ports for the supported port identifier characters.
//
//   The timeout value must be at least 3000 msecs. The default com timeout 
//   is 5 seconds.  A few devices extend the com timeout values to 10 to 25 
//   seconds while doing commands that take a long time to do (like receiver 
//   diagnostics and hard resets).  If you don't use those commands, 
//   the "/ct" commands allow you to set a shorter timeout.  Shorter timeouts 
//   make automatic recovery from dropped com links faster.
//
//   Note that under Windows if you drag the window for more than the
//   com timeout period you will get a data loss error!
//
//   Heather now has the "!x" keyboard command for setting the receiver 
//   baud rate for devices that support raw satellite data.
//   IF YOU SET THE RECEIVER TO A NON-DEFAULT VALUE YOU WILL NEED TO SPECIFY
//   THE BAUD RATE ON THE COMMAND LINE (/br=...) WHENEVER YOU START HEATHER.
//   If the receiver type can be auto-detected and the baud rate is one of
//   the supported auto-detect rates (9600,19200,38400,57600,115200 baud),
//   tnen you might not need to specify the baud rate.  
//
//   You can also use the "brx=baud_rate" command line option to set the
//   receiver baud rate from the command line.  The /brr command MUST come
//   after the /rx?? command line option that sets the receiver type (so that 
//   Heather knows which command to send to the device).
//
//   The !x and /brr commands currently only change the receiver baud rate.
//   They do NOT change the data_bits, stop_bits, or parity settings!
//
//
//
//-EXTERNAL / EXTRA DEVICE SUPPORT
//
//   Besides the main "receiver" device, Heather has support for and hooks
//   for adding extra devices (such as counters, environmental sensors, and
//   echoing device data to other devices).  These external device ports are
//   configured using the /e? command.
//
//   /ed  DAC/ADC port
//   /ee  receiver data echo port
//   /ef  temperature control device
//   /ei  secondary interval/frequency counter
//   /ek  NMEA echo port
//   /en  environmental sensor port
//   /er  the standard "receiver" device
//   /et  moon / sun / sat position tracking info
//   /e0 .. /e9 - for user defineable devices
//
//   The syntax for the /e? command is shown below using /ei as an example:
//
//      /ei=device
//
//   Where "device" can be a serial port descriptor like:
//      /ei=1   (com1)
//      /ei=1u  (usb0)
//      /ei=3,9600:8:N:1   (com3 at 9600 baud, 8 bits, no parity, 1 stop bit)
//
//      You can also configure the baud rate for the external devices by
//      using the ":P#" parameter on the /br= command like this example for
//      the NMEA echo (/ek) port:
//         /br=19200:8:N:1:PI
//
//   Where "device" can be an IP address AND a non-optional port number.
//   Heather uses the presence of a ':' in the device parameter to recognize
//   that it is a IP address.  The IP address must lead to a connection that
//   is lisenting for data, otherwise Heather can lock up waiting for the
//   connection or a timeout occurs.
//       /ei=123.135.146.157:45000
//       /ei=example.com:45000
//
//   Where "device" is a Linux style device name:
//       /ei=/dev/ttyUSB0
//       /ei=/dev/ttyUSB1,9600:8:N:1
//
//   The only external devices that Heather currently has full/tested support
//   are:
//
//       /ee - receiver echo port.  This port echoes the receiver data
//             stream to the port.  The default data format of the echoed
//             data is whatever the main "receiver" device is configured for.
//             Any data sent to the echo port by the connected device is
//             currently ignored by Heather.
//
//       /ef - temperature control device (fan) port.  Heather defaults to
//             using the receiver data port modem control DTR/RTS lines
//             for its temperature control function.  The /ef command lets
//             you specify a different port.  This can be useful if the
//             main receiver port does not have modem control signals (like
//             some USB interfaced receivers).
//
//       /ei - the secondary time/frequency counter port.  If the main
//             "receiver" is a counter (/rxi or /rx1), the /ei command lets
//             you use a second counter for processing up to two more channels
//             of time/frequency data (or four channels with a TAPR TICC).
//             Note that Heather has no way of configuring the secondary
//             counter configuration operating mode.  Also the user must
//             configure the main and secondary counters with the same
//             settings and operating mode.  To configure the second TICC
//             start Heather with the second device's port specified as the 
//             main input device, configure it, shut down Heather, then
//             restart Heather with the first TICC specified as the main
//             device and the second TICC as the extra device.
//
//             If the main receiver device is a GPS receiver or GPSDO, the
//             data from the "secondary" /ei counter device is used to
//             calculate true adevs instead of the "bogo-adevs" that are 
//             derived from the GPSDO self-reported loop control statistics.
//             When Heather is calculating "bogo-adevs" the adev type is
//             shown in lower case.  Upper case is used for "TRUE" counter
//             derived adevs.
//
//             See the description of the /im#, /if#, and /it# commands for
//             specifying what type of data the counter is sending, the
//             frequecy of the oscillator being tested, and forcing the
//             counter type.
//
//       /ek - the NMEA echo port.  This port echoes the current receiver
//             position, time, and satellite infomation in standard NMEA
//             format.  This lets you send the receiver data to another
//             program that understands NMEA but does not understand the
//             data the the receiver is sending.
//
//       /en - to read data from an external environmental monitor device
//             that provides temperatures (up to two), humidity, and air 
//             pressure.  Currently supported sensors are the USB sensors
//             from dogratian.com  amd the LFS10x devices from 
//             LookingForSolutions.com (like the LFS104BW).  A future 
//             Heather-specific/optimized sensor is planned.
//
//       /er - the main receiver data port.  This is the same as the port
//             set by the /1, /1u, /id, /ip etc commands.  The /er command 
//             just provides an alternate way of specifying the receiver
//             data connection.
//
//       /et - outputs the selected sun / moon / sat position info
//             out the TRACK_PORT.  Can also output the time in UTC.
//             This can be useful for implementing moon/sun/satellite trackers.
//             Once the TRACK_PORT is open and outputing data the SUN AZ:
//             SUN EL: / MOON AZ: / MOON EL: labels on the screen will be
//             shown in upper case if that info is selected for output.
//
//
//   Future device support:
//
//      /ed - to provide control and monitoring of an external device that
//            has DACs and/or ADCs for monitoring and controlling analog
//            devices.
//            
//
//
//
//-USING A SIMULATION INPUT FILE:
//
//   You can force Heather to get its input data from a file.  These are
//   typically receiver data capture files captured by Heather using the WY
//   keyboard option.  Simulation files do not work with most of the "polled"
//   receiver types such as SCPI that require two-way polling to get data 
//   from the receiver.  They mostly work with "UCCM" type receivers that
//   echo the commands sent to the receiver, but there will be a "time skip"
//   indication every second.
//
//   To use a simulation input file, use the /rs command line option:
//     /rs=filename  -or-
//     /rs=filename,seek_addr
//
//     ",seek_addr" is optional and if specified seeks to that byte in the
//     simulation file before reading.  This lets you skip over data you are
//     not interested in.
//
//   You should also specify "/0" on the command line to disable the com 
//   port, but this is not usually necessary.
//
//   You can also read .raw simulation files with the keyboard "R" command.
//   This does not require the /0 command to disable the serial port.
//
//   If the simulation file was read in via the /rs= command line option,
//   the WU keyboard command will pause reading the file.  If the file was
//   read in via the "R" keyboard command, WU will close the simulation file
//   and resume normal processing of the receiver data stream.
//
//   You can use the /sw= command line option to control how fast the 
//   simulation file is processed.  The value is the delay in milliseconds
//   to wait after each message is read.  Using the /sw command can make
//   keyboard response rather sluggish.  You can slightly speed up reading 
//   of a simulation file by doing something that causes the plot area to
//   not be drawn like pressing the "G" key to bring up a keyboard menu.
//   As long as the menu is being shown, the simulation runs a little faster.
//   Also, if the mouse cursor is in the plot area of the screen reading the
//   simulation file can slow down quite a bit.
//
//
//   You can also simulate a time interval counter connected as an "extra"
//   input device using the /ri command.  If you do this you MUST also
//   specify the time interval counter type using the /it? command.
//     /ri=filename  -or-
//     /ri=filename,seek_addr
//
//
//
//-CONFIGURING THE RECEIVER TYPE:
//
//   Heather supports numerous receiver types.  If you do not specify a 
//   receiver type Heather will attempt to automatically determine 
//   the receiver type.
//
//   Auto-detection requires the receiver to be actively sending data that
//   can be analyzed.  Some receivers power up "mute" and do not automatically
//   send data.  You must "wake up" these receivers first by specifying the
//   receiver type.  Also some receivers ("polled receivers") only send data 
//   in response to a query message.
//
//   If the receiver can work in both a NMEA and a native
//   binary format, it probably powers up in NMEA.  Use the
//   proper /rx# command shown below to put the receiver into native binary
//   mode.  Binary mode offers the user full control of the receiver
//   and better monitoring options.  The "!m" keyboard command can
//   switch most receivers back to NMEA mode.  On some receivers
//   it swicthes the device to its alternate language.
//
//   Some Motorola receivers power up in NMEA mode, sometimes at 4800 baud.
//   Receiver type auto-detect does not try 4800 baud.  If you are using a
//   Motorola receiver and it does not auto-detect, try starting Heather with
//   the /br=4800 command line option.   You can switch Motorola receivers
//   that are in NMEA mode to binary mode using the "!n" keyboard command.
//
//
//   You can force the receiver type with the "/rx" command line option.
//      /rx   - auto-detect receiver type (default)
//      /rxa  - Acron Zeit WWVB receiver (300:8:N:2)
//      /rxai - Trimble ACE-III (9600:8:O:1)
//      /rxag - Trimble Acutime GG (9600:8:O:1)
//      /rxat - Trimble Acutime Gold and earlier versions (9600:8:O:1)
//      /rxa3 - Trimble Acutime 360  (115200:8:O:1)
//      /rxb  - Brandywine GPS-4 receiver - 4800:8:N:1
//      /rxca - calculator only mode
//      /rxc  - UCCM - Trimble / Symmetricom / Samsung GPSDOs - 57600:8:N:1
//              (auto-detect sub-type)
//      /rxcp - UCCM-P - Trimble / Symmetricom GPSDOs - 57600:8:N:1
//      /rxcs - UCCM LPK/L8 - Samsung GPSDOs - 57600:8:N:1
//      /rxcu - UCCM - Trimble / Symmetricom GPSDOs - 57600:8:N:1
//      /rxd  - DATUM STARLOC II GPSDO - inferior wannabe Thunderbolt
//      /rxe  - NEC GPSDO ... STAR-4 compatible at (115200:8:N:1)
//      /rxen - Environmental sensors
//      /rxes - Furuno eSIP receivers
//      /rxf  - Lucent RFTG-m GPSDO
//      /rxfu - Furuno GT-8031 (using $PFEC commands)
//      /rxg  - GPSD interface (not really a Windows thing - /ip=localhost:2947)
//      /rxh  - HP 5071A cesium beam oscillator
//      /rxi  - TAPR TICC time interval counter (115200:8:N:1)
//      /rxj  - Jupiter-T  (aka Zodiac)
//      /rxk  - Lucent KS24361 REF0/Z3811A (19200:8:N:1)
//      /rxl  - Jackson Labs LTE Lite (38400,8,N,1)
//      /rxlp - Temex/Specratime LPFRS or RMO rubidium  (1200:8:N:1)
//      /rxm  - Motorola binary 
//      /rxn  - NMEA
//      /rxo  - TruePosition GPS
//      /rxp  - Trimble TAIP receivers (4800:8:N:1)
//      /rxpa - Trimble Palisade (9600:8:O:1)
//      /rxpp - Tom Van Baak's PICPET timestamping counter chip
//      /rxpr - SRS PRS-10 rubidium oscillator
//      /rxr  - Trimble Resolution T family with odd parity
//      /rxs  - Sirf binary
//      /rxsa - Symmetricom SA22.c rubidium with 60 Mhz osc (forced model type)
//      /rxsb - Symmetricom SA22.c rubidium with 58982400.0 Hz osc (forced model type)
//      /rxsy - Symmetricom X72/X99/SA22 rubidium (60 Mhz osc) (auto detect model)
//      /rxss - Novatel SuperStar II (19200,8,N,1)  - currently untested
//      /rxsr - Spectratime SRO100/SRO70 rubidium 
//      /rxt  - Trimble TSIP binary, 
//      /rxtb - terminal emulator only (with buffered keyboard).
//      /rxte - terminal emulator only.
//      /rxtm - Spectrum TM4 GPSDO (setting features untested)
//      /rxts - TymServe 2000.
//      /rxu  - Ublox UBX binary, 
//      /rxut - Ublox UBX binary (with TP5 timing messages), 
//      /rxv  - Venus/Navspark mixed binary / NMEA (115200:8:N:1)
//              (auto-detects timing/RTK models)
//      /rxvb - Venus/Navspark RTK receiver in BASE mode (115200:8:N:1)
//      /rxvp - Motorol Oncore (VP) receiver
//      /rxvr - Venus/Navspark RTK receiver in ROVER mode (115200:8:N:1)
//      /rxvt - Venus/Navspark timing receivers (115200:8:N:1)
//      /rxx  - No receiver, uses system clock. 
//      /rxx7 - Symmetricom X72 rubidium (forced model type)
//      /rxx9 - Symmetricom X99 rubidium (forced model type)
//      /rxy  - SCPI - Nortel telecom GPSDOs like NTWB and NTPX
//      /rxz  - SCPI (Z3801A style. 19200:7:O:1)
//      /rx5  - SCPI (HP5xxxx style)
//      /rx0  - Gravity/solid earth tide clock (uses system clock to display 
//              solid earth tides and gravity offset,  requires manual entry
//              of latitude/longitude/altitude)
//      /rx1  - HP531xx (or other) counter (9600:8:N:1)
//      /rx12 - Ashtech Z12 L1/L2 GPS receiver
//      /rx17 - Trimble RT17 format GPS receivers (115200,8,N,1)
//      /rx3  - Zyfer Nanosync 380 (19200:8:N:1)
//      /rx35 - Symmetricom SA.35m rubidium(57600:8:N:2) - code not completed
//      /rx4  - Oscilloquartz STAR-4 GPSDO (9600:8:N:2)
//      /rx45 - Oscilloquartz OSA-453X GPSDO (9600:8:N:2)
//      /rx6  - Trimble SV6/SV8 (9600:8:O:1) (also ACE-III)
//      /rx8  - NVS BINR binary (115200:8:N:1)
//
//   /rx says to auto-detect the receiver type. This tries
//   to find the receiver type at 9600:8:N:1, then
//   115200:8:N:1, then 57600:8:N:1, then 19200:8:O:1, then 38400:8:N:1 
//   unless the user specified the com port parameters
//   (with the /br=... command) before the /rx option. Note that for Z3801A
//   receivers that use 19200:7:O:1,  the auto-detect routine detects the
//   incorrect data size/parity combination and uses the proper settings).
//
//   /rx (auto detect) is the default mode if no /rx? command
//   is given on the command line.
//
//   Note that the auto-detect routine is a bit simplistic
//   and might occasionally mis-recognize the receiver type.
//
//
//   You can force or set the UTC leapsecond offset with the /rx? commands
//   like /rxx=18 (sets the leapsecond offset to 18 seconds).  This is
//   useful for devices that do not report the leapsecond offset or report
//   an invalid value.
//
//
//   If you explicity specify the receiver type, Lady Heather
//   defaults to the baud rate indicated above (or 9600:8:N:1 if
//   not shown above).  If your receiver is configured for
//   a different baud rate, specify the serial port settings
//   to use with the /br= command line option.
//
//   
//
//   Special notes for Trimble Resolution-T (and other) TSIP devices:
//   Resolution-T devices default to ODD parity.  Heather can recognize the
//   TSIP data stream even if set for EVEN/NO parity, but the Res-T will not
//   recognize commands sent to the device.  If you let Heather auto-detect
//   the receiver type and did not specify a baud rate then, after around 
//   30 seconds and the receiver ID message has not been seen (which the 
//   receiver sends only if it accepts a query command) Heather will 
//   automatically try different parity settings.  This feature may not 
//   always work and is a bit of a hack.  Also, the screen and some receiver
//   options may not be properly configured for the new receiver type.  The
//   screen can usually be configured properly by issuing a screen size
//   command from the $ keyboard menu) once Heather has properly detected
//   the receiver serial port settings and has determined the actual receiver
//   type.
//
//   If you are using a Trimble Resolution-T type of receiver, you can
//   force the receiver model and/or ODD parity with the /rt command line
//   option.  The /rt command line option should be used with the /rxt and
//   /rxr command line options or if the device is not properly auto-detected.
//      /rt   - use ODD parity on the serial port and config for Res-T devices.
//      /rt=1 - Resolution-T
//      /rt=2 - Resolution-T SMT
//      /rt=3 - Resolution-T RES
//      /rt=4 - Resolution-T 360
//      /rt=5 - Resolution-T ICM
//
//
//
//   Special notes for Trimble RT17 format receivers (like the NetRS):
//   Receiver ports configured for RT17/Trimcom format outputs seem to only
//   stream data.  I have been unable to send configuration, etc commands
//   to the receiver.  Thus Heather is currently a monitoring only program
//   for these receivers.  You cannot change the receiver configuration or
//   request information that the receiver does not automatically stream.
//   You must make all configuration changes via the NetRS built-in http 
//   web server.
//
//   Heather can auto-detect RT17 receivers as Zodiac receivers.  It is
//   best to force the receiver type with the /rx17 command line option.
//
//   It can take a few seconds to connect to the receiver over a TCP/IP
//   connection.  You can configure the device's IP address by connecting
//   a serial port (115200,8,N,1) to the RS-232 connector on the front panel.
//   Use a terminal program (or Heather with the /rxtt /br=115200 command
//   line option) and power up the receiver.  You should see lots of messages
//   fly by.  Near the end of the boot sequence it will ask if you want to
//   change the IP address.  Note that some of the serial ports on the rear
//   panel are straight-through connections and others are null-modem
//   connections.  Some NetRS manuals are incorrect in specifying which are
//   which.  It is suggested to use the front panel connector for boot-up
//   monitoring and use a rear panel connector to talk to Heather.
//
//   It is suggested to update NetRS receiver firmware to the latest available
//   (ver 1.3-2)  This firmware was a "security" upgrade and includes several
//   fixes to earlier versions.  It will work on all receivers regardless of
//   their "warrenty" date.   UNAVCO.COM has lots of info on using the NetRS
//   receiver.
//
//   Suggested port message confiuration is RT17 data with:     
//      1 Hz epochs, position and measurement data
//      Concise format
//      Send RAW GPS data
//      Send Ephmeris data data (not used by Heather, may be useful to other
//      programs).
//      Send IODE and cycle slip counts.
//      Smooth code phase
//      Smooth carrier phase
//
//   If you connect an external frequency reference to the NetRS, you must
//   enable it.  Leaving it connected but not enabled can affect performance
//   or interfere with satellite tracking.
//
//   Trimcomm messsage format configured ports do not send location data, 
//   so use RT17 format.  Trimcom data is only available over the TCP/IP 
//   port (default 5018).
//
//   Heather supports writing L1/L2 RINEX files from the RT17 data stream.
//   Note that the RT17 format does not output a GPS week number.  Heather
//   creates a week number from the system clock.  This is used in conjunction
//   with the GPS time-of-week value in the receiver raw data packet to 
//   generate the time display and RINEX files timestamps. If the system clock
//   is inaccurate, the date will be wrong close to the GPS end-of-week.
//   This can cause glitches in the RINEX output... so don't collect RINEX 
//   files that span the GPS week rollover period.  For RINEX output don't
//   select L2C data.  RINEX v2.xx does not know about L2C and Heather's 
//   RINEX v3.xx support is currently incomplete (the observation list does
//   not output the correct v3.xx observation codes... you could manually
//   edit the file, though).
//
//
//
//   The Acron Zeit WWVB receiver cannot be auto-detected.  Always use
//   the /rxa command.  Support for this receiver is a hack.  Heather shows
//   it as tracking sat PRN 1. You should manually enter your lat/lon/altitude
//   (/po=lat,lon,alt command line option or the SL keyboard command or the
//   "heather.loc" file) and the utc offset (like /rxa=17 or /uo=17 command 
//   line options). If you don't enter your position, sat PRN 1 is shown 
//   at az=1, el=89. Technically the Acron Zeit speaks at 300:7:O:2, but it
//   also works with 300:8:N:2 if you strip off the received parity bit 
//   (which Heather does). Also, it takes several seconds for Heather to 
//   startup and shutdown with this device under Windows.
//
//
//
//   Special note for Acutime 2000 and earlier receivers... also the Palsiade:
//   You MUST specify the /rxat (or /rxpa) and /rxag  receiver type command
//   line option. If you auto-detect the device or specify an incorrect 
//   TSIP receiver device, the Acutime can be put into a mdde where it 
//   sends TSIP messages without proper end-of-message indicators.  If this
//   happens, the screen data areas will go blank and you must power-cycle 
//   the receiver to recover!  Also, note that changing most of the settings
//   on these receivers cause them to do a restart and the seetings changes
//   do not show up for several seconds.
//
//
//
//   Special note for the Ashtech Z12 receiver:  If the Z12 is configured to
//   send the NMEA GPZDA time code message, the time code messages will
//   corrupt the raw satellite data observation message... so Heather uses the
//   system clock to display the time.  This can make it appear that Heather
//   is actually receiving data from the Z12.  To verify that Heather is
//   actually talking to the Z12, make sure that the receiver ID, firmware,
//   and option info is being displayed.  If raw observation messages are
//   enabled you should also see satellite positions, signal strength, and
//   doppler data being displayed.
//
//   The Z12 has no way to read back the satellite elevation mask filter.
//   If you are unsure of the current setting, set the filter (FE command).
//
//
//
//   The Brandywine GPS-4 cannot be auto-detected.  Also the baud rate
//   must be set to 4800:8:N:1  since the Brandywine receiver cannot accept
//   more than 1 char per millisecond.  The Brandywine receiver will not
//   work with most serial cables.  Pin 4 is a receiver reset signal and if
//   connected will prevent the receiver from working.  Pins 6, 8, and 9
//   also have non-standard uses.  YOU SHOULD USE A CABLE WITH ONLY 
//   PINS 2, 3, and 5 CONNECTED TO THE PC!  The Brandywine receiver does
//   not work well with the audible "tick clock" mode.
//
//
//
//   The Datum STARLOC II cannot be auto-detected. Firmware
//   bugs cause it to stop outputting time messages. Always
//   specify "/rxd" when running STARLOC II receivers.  Also
//   note that the Datum STARLOC II has NUMEROUS firmware
//   bugs and generates lots of duplicate/missing time stamp errors
//   and does not output satellite azimuth/elevation values.  The
//   firmware bugs cause many messages to be corrupted (the firmware does not
//   properly "escape" any 0x10 bytes in most of the output messages, etc),
//   thus any messages that contain a 0x10 byte are likely to be corruped!
//   There might be firmware out there that fixes these issues, but I have
//   not seen any.  The STARLOC is the most miserabe excuse for a GPSDO that
//   i have ever seen... the firmware seems to have been written/tested by a
//   drunk chimanzee... I have fw App:1.10 16 Mar 2000, GPS:1.2 07 Jan 2000.
//
//
//
//   Special note for Furuno (like GT-8031 and eSIP) receivers:  Auto-detect
//   may detect these as NMEA receivers, particularly if Heather has not
//   previously enabled them.  YOU SHOULD NOT RELY ON AUTO-DETECTING THESE
//   RECEIVERS!  Also, these receivers may not output any data until
//   they begin tracking satellites and have an almanac.  They may be
//   unusable/undetectable for a long time (an hour?) after power-up.
//
//   The Furuno PFEC model and version info is only available from the
//   self-test results message.  If the diagnostics have not been run they
//   will show up as "0". Running the diagnostics will affect the receiver
//   operation for a few seconds.  The diagnostics are run whenever
//   Heather starts up, so for the first few seconds you may see 
//   "No stats usable" and "Time invalid" messages.
//
//   For ESIP receivers, the SU keyboard command can be used to set the
//   default UTC (leapsecond) offset to use when the receiver does not have
//   the current value from the satellies.  This value is saved in EEPROM.
//
//   Furuno ESIP receivers (like the GT87xx series) have some satellite
//   data messages (that send things like satellite doppler, pseudoranges,
//   and the raw navigation message that are only avialable if the baud rate 
//   is 115200 baud or greater.  
//   You can set the ESIP baud rate by using the "!u" keyboard command to
//   send the following string (in uppercase!):
//      PERDCFG,UART1,115200
//   Note that the baud rate, cable delay, signal level mask, elevation
//   mask, etc settings are NOT stored in flash memory and will be lost
//   after a power cycle (unless a backup battery is in use).  Also after
//   changing the baud rate, you will need to specify the baud rate from
//   the command line (because Heather assumes ESIP receivers run 
//   at 38400 baud):
//       /rxes /br=115200
//
//
//
//   GPSD is a Linux/macOS/FreeBSD service that provides a standardized
//   interface to numerous models of GPS receivers. It is accessed
//   via TCP/IP address "localhost:2947"  GPSD cannot be auto-detected.
//   Use "/rxg" to force GPSD mode.  You can specify a particular
//   GPSD device to use with the /ig=gpsd_device_name command.
//   The /ig command will also do the /rxg command.
//   If your GPSD system is not on "localhost:2947", specify the TCP/IP
//   address with the /ip= option after the /rxg or /ig= option.
//
//
//
//   The Jackson Labs LTE GPSDO device has a Venus timing receiver in it that
//   runs at 38400:8:N:1 and normally generates the standard Venus messages. 
//   It also has a switch that enables a proprietary Jackson Labs STATUS 
//   message.  On earlier versions of the LTE firmware enabling the STATUS 
//   messages disables all the Venus messages and you lose the ability to 
//   show satellite info, automatically get the UTC.  etc.  Later versions 
//   of the LTE firmware allow the STATUS message to be mixed in with the 
//   regular Venus messages.leapseoncd offset, etc.  In STATUS only mode 
//   Heather gets the time from the receiver clock.  Note that the LTE does
//   not let you control the Venus receiver and you cannot change any
//   settings or request data from the receiver.  Because of this, Heather
//   cannot get the UTC leapsecond offset.
//   
//
//
//   Special note for Lucent KS24361 units: the Z3811A
//   (REF1) unit talk SCPI at /br=19200:8:N:1 and the
//   Z3812A (REF0) unit talks at /br=9600:8:N:1 over the
//   DIAGNOSTIC ports.  
//
//
//
//   Special note for Lucent RFTG-m units: the RFTG-m units output
//   control and staus messages in TSIP format and a time code in ASCII.
//   Heather attempts to disable the TSIP messages when it exits so that
//   the device can be auto-detected when Heather starts.  If a program
//   (such as the Lucent RFTG control program) left the device outputting 
//   TSIP, it will be mis-identified.  If this happens, you should use 
//   the /rxf command line option to force the receiver type to RFTG-m.
//
//   You can use the !D and !R commands to force disable or re-enable a unit.
//   If you disable a unit,  the other unit the other unit will be in 
//   control.  If both units are enabled, then the RFTG firmware decides 
//   which unit is in control (usually the Rb unit).  If both units are
//   disabled, well... not much happens.  Heather will not see any data
//   on the serial port and after a few seconds will try to re-establish
//   communications... which won't suceed.  Try !R to re-enable the unit.
//   Or you may have to power-cycle the device.
//
//   Also, The RFTG units do not output satellite positions so the normal 
//   signal level maps are not available. On the RFTG-XO unit Heather will 
//   show  the satellites being tracked and the signal levels, but the
//   satellite positions are fixed at AZ=(prn*10) and EL=20 degrees.
//
//   If you enter "& ESC" the rather useless satellite info table will be 
//   replaced by a much more intersting paramter info table.  If you press
//   ESC or SPACE, the display will revert to the sat info table.  Clicking
//   on the sat info table or issuing the ZD keyboard command will zoom the 
//   screen to show the device paramter info screen.
//
//   Also, you will need to run two instances of Heather to monitor both
//   sides (RB and XO) of the unit at the same time.
//
//
//
//   Some Motorola receivers power up in NMEA mode, sometimes at 4800 baud.
//   Receiver type auto-detect does not try 4800 baud.  If you are using a
//   Motorola receiver and it does not auto-detect, try starting Heather with
//   the /br=4800 command line option.   You can switch Motorola receivers
//   that are in NMEA mode to binary mode using the "!n" keyboard command.
//
//
//
//   Some NMEA receivers use 4800 baud baud.  Receiver type auto-detect does 
//   not try 4800 baud.  If you are using a NMEA receiver and it does not 
//   auto-detect, try starting Heather with the /br=4800 command line option.   You can switch Motorola receivers
//   
//
//
//   The NV-08C receiver powers up "mute".  It cannot be auto-detected until
//   it has been initialized (start Heather with the /rx8 command line
//   oprion).  Also the auto-detect routine might possible identify
//   the NVS-08 as a Trimble TSIP receiver... their comminications protocols
//   are virtually identical.  The NV-08C has two serial ports.  One outputs
//   NMEA data, the other uses NVS BINR binary format.  You should use the
//   binary format port.  Some NVS receiver modules have a switch for seleting
//   the NMEA or BINR port.
//
//
//
//   Special note for OSA-453x rubidium oscillators:  these cannot be auto
//   detected.  Also, some versions of the firmware time out after 175 msecs
//   between keystrokes... you can't manually send commands to the device
//   with a standard terminal program!  The !t terminal emulator command 
//   attempts to buffer all keystrokes and sends the buffer when CR is
//   pressed. The /rxtt terminal-only mode does not currently support this 
//   feature... use /rxtb for a buffered terminal-only mode keyboard.  
//
//   Due to the slow baud rate and the length of the response to the "V" 
//   version info command, the version info is only requested when Heather 
//   starts up (otherwise you would see lots of time stamp errors).  Speaking
//   of which, the 453x devices have some firmware issues... the message
//   that outputs position/time regularly gets corrupted.  Heather can usually
//   patch things up.  Also the 453x's also regularly stops responding to
//   queries, so you will probably see DATA LOSS RESETS.
//
//
//
//   Note that many PRS-10's have the serial data and 1PPS input pins 
//   configured to output analog data.  To configure the pins for serial 
//   data and 1PPS inputs you must change some resistors inside the unit 
//   (Hey SRS! ever hear of jumpers and solder blobs for doing config 
//   changes?  Bsstards!)
//   You might want to disable the digital clock display... you will then
//   be able to see all the ADxx values on the main screen.
//   The ZD command will zoom the screen to show all values read from the
//   device.
//
//
//
//   Special note for SRS PRS-10 rubidium oscillators: the PRS-10 cannot be
//   auto detected.  It takes around 25 seconds to request and receive all
//   of the information it can provide.  The plot queue is automatically
//   reset the first time all of the available infomation is received.  This
//   is done because the plot queue will contain bogus zero values for any 
//   data that had not yet been received.  
//
//   
//
//   Special note for the Oscilloquartz Star-4: When the Star-4 is first
//   powered up, it does not send time/position info until it receives a 
//   warm-restart command.  This causes the receiver to go do a self-survey
//   and start sending time/position information.  Heather detects that
//   the device has not been initialized by detecting the loss of time
//   messages for over 16 seconds.  The first time you start Heather after
//   poweing up the Star-4, it can take around 20 seconds before normal
//   operation is established and the screen starts updating.
//
//
//   Special note for Samsung UCCM receivers like the -LPK and -L8:
//   These receiver will report "Power Bad" unless the input voltage is
//   within a rather narrow range around 5.5V.  I power mine from a 6.0V
//   supply fed through a (5A) Schottky power diode.  The device does seem
//   to work properly from 5V .. 6V even though it reports "Power Bad".
//   Some people have reported locking issues at 5.0V.  
//   These devices will do a self survey every time they power up... this
//   takes around 40 minutes to complete.  Settings such as cable delay 
//   and antenna elevation mask are saved in EEPROM.
//
//
//   Special note for the Spectratime SRO100/SRO70 rubidium oscillators:
//   these cannot be auto detected.  The plot queue is automatically reset
//   the first time all of the available information is received.  This
//   is done because the plot queue will contain bogus zero values for any 
//   data that had not yet been received.  
//   You might want to disable the digital clock display... you will then
//   be able to see more of the SRO100 status values on the main screen.
//   The ZD command will zoom the screen to show all values read from the
//   device.
//
//
//   Special note for the Spectrum TM4.  Support for this device has not been 
//   fully tested... I don't have one.   If you set the cable delay value
//   with the PC keyboard command it will set the MUX1 output for PPS output
//   (enabled or disabled).  If you had the output configured for a frequency
//   or time code (P1 command) you will need to redo that setting.  Also note
//   that the TM4 does not send satellite positions... the satellite position
//   and signal level maps are not available...  boo! hiss!
//
//
//
//   The TAPR TICC must have the latest firmware to work with Lady Heather...
//   the firmware shipped with the first batch of TICCs (and maybe the 
//   second production run?) will not work. Auto-detecting the TAPR TICC 
//   can be unreliable, particularly on non-Windows machines.  Other counter
//   types (except the PICPET) cannot be auto-detected... you must use 
//   the /rxi command line option.
//
//   For TAPR TICC devices.  Heather defaults to the "all adev" display
//   display for channel A data.  The GP plot is the channel A time interval
//   deviation from 1 second (in nanosecods).  GO is channel B.  G7 is channel
//   C. G8 is channel D.  The current TAPR TICC is a two channel device and
//   does not ouput chC and chD data but Heather allows two TICC devices to be
//   used.  The first one is the main "receiver" device (the /rxi device) and
//   the second one is the "external" device (specified the the /ei= command
//   line option).  In this mode the data from the secondary TICC chA and chB
//   are processed as chC and chD.
//
//   Although the current TAPR TICC can output channel C timestamps when set 
//   to "TIMELAB" mode, these are meaningless for Heather's ADEV analysis and 
//   support is mainly for curiosity.
//
//
//   If the Trimble SV6/SV8/ACE-III is auto-detected,  it will first be 
//   recognized as a TSIP device but the parity will be wrong and it won't 
//   accept commands. Also, the special commands the SV6 expects won't be 
//   used.  After 30 seconds or so, Heather will automatically try odd 
//   parity (you should hear a beep) and the receiver should mostly work.
//   For the most reliable operation, use /rx6 or /rxai  with these devices.
//
//
//   The Trimble SV6 and related devices do not output data until they
//   are tracking satellites.  They must have an antenna connected and may
//   need to be powered up for 20+ minutes before they can be used.  Also
//   they do not accept a lot of the standard TSIP receiver control commands
//   (even though they may be shown in the various keyboard menus).
//
//
//   Trimble TAIP receivers cannot be auto-detected if the baud rate is
//   the standard 4800 baud.  TAIP receivers do not output satellite 
//   positions or signal levels.  The sats show up in the sat maps at 
//   az=10*prn, el=30 degrees,  sig level=40.0
//
//
//
//   Special note for Trimble Resolution-T devices:
//   These are commonly available configured for ODD parity. Heather attempts
//   to detect this when it thinks it sees a Resolution-T by issuing commands
//   and if it does not see expected responses, it toggles the parity mode and
//   tries again.  This repeats every 30 seconds or so.
//   The "/rxr" command sets parity to ODD.  
//   Also Resolution-T devices can have firmware that makes identifying the 
//   exact model number impossible. If you have problems, you can force the 
//   model type:
//      /rxr=1  - original Resolution-T
//      /rxr=2  - Resolution-T-SMT
//      /rxr=3  - Resolution-T-RES
//      /rxr=4  - Resolution-T-360
//      /rxr=5  - ICM
//
//   The Trimble Resolution-T TEP model is configured to speak Motorola binary
//   (rather poorly).  The !M keyboard command will switch it to TSIP mode.
//   A hard reset (!H) will do a factory reset back to Motorola mode.
//
//
//
//   Special note for Trimble telecom GPSDOs like the NTWB and NTPX: these
//   devices can speak either TSIP binary (/rxt) or SCPI (/rxy).  TSIP
//   provies much more information and a much more robust interface.  
//   Auto-detect will find these units as TSIP devices.
//
//
//
//   The TruePosition GPSDO has factory and warm reset commands, but these
//   dont seem to restore things like cable delay and attenuator settings
//   to their default values.
//
//
//
//   Special note for Ublox receivers:  Later models of the Ublox receivers
//   use the CFG_TP5 message to config the PPS and TIMEPULSE outputs.  Heather
//   can automatically detect the receivers and use the proper message. But
//   if you use the '@P...' command in a heather.cfg file to config the pulse
//   outputs on startup Heather will not yet know the exact receiver type.
//   You can use the /rxut command line option to force Heather to use the 
//   CFG_TP5 commands.  Also Ublox receivers can send mixed NMEA and binary
//   messages.  This can confuse the auto-detect routine into reporting the
//   receiver as a NMEA receiver (particulalry if the receiver is configure
//   for multiple GNSS systems) .  Use the /rxu command line option to force
//   Ublox mode and prevent this.
//
//
//
//   Special note for Venus/Navspark RTK receivers.  These receivers need to
//   be put into base or rover mode before they will send RTK/RAW data. A 
//   RTK receiver that is in a RTK mode will show the device as "Venus-R" (the
//   Venus timing receivers show as "Venus-T").  Heather tries to enable
//   base mode when it initializes the receiver.  If this does not work 
//   (sometimes the receiver seems to ignore the command) you can try
//   the !k keyboard command which will re-send the base mode command.  If
//   the receiver is in ROVER mode when Heather is started, it cannot be
//   auto-detected.  If you are using a Venus RTK receiver it is best 
//   to start Heather using one of the following commands.  Heather will
//   force ROVER mode if you dont use one of these commands.
//      /rxvb - for BASE mode
//      /rxvr - for ROVER mode
//
//   The !k command lets you enable binary RTCM output mode.  If this is
//   selected then Heather will stop seeing valid messages, timeout, and 
//   re-start the receiver.  The re-start will disable RTCM output mode.
//   If you wish to keep RTCM output enabled you MUST exit the program before
//   the timeout (5 seconds).  Whenever Heather starts up, RTCM output is
//   disabled.  Heather cannot auto-detect a receiver that is in RTCM
//   output mode.
//
//
//
//
//   Special note for X72/SA22 rubidium oscillators: these cannot be
//   auto detected.  The plot queue is automatically reset the
//   first time all of the available infomation is received.  This
//   is done because the plot queue will contain bogus zero values for any 
//   data that had not yet been received.  
//   You might want to disable the digital clock display... you will then
//   be able to see more of the X72 status values on the main screen.
//   The ZD command will zoom the screen to show all values read from the
//   device.
//
//   Most X72/SA22.c devices use a 60 MHz oscillator and generate a 10 MHz
//   output.  Some telecom models (ussualy SA22.c devices... use a 58.982400 
//   oscillator and generate a 9.8304 MHz output.  The /rxsb command line
//   option configures Heather for these units.  If you happen to have a
//   X72 with these "telecom" frequencies try /rxsb /rxsy.  Note the "i"
//   status command reports clock frequencies that have no relation to
//   reality!
//
//   The X72/SA22 firmware does not have a way to read back a lot of the
//   current configuration settings.  Heather implements a "software eeprom"
//   that stores the current settings in the file "tbeeprom.dat".  If you
//   use more than one X72 and/or SA22 device you should start up Heather
//   with the "/wp=xxx" (write prefix) command line option that specifies
//   which software eeprom file to use with that device.  For instance 
//   "/wp=sym" will use the file "symeeprom.dat", /wp=xyz will use the file
//   "xyzeeprom.dat", etc.
//
//
//
//   Special note for Zyfer Nanosync units: these power-up "mute" and do not
//   send any data until commanded.  The unit cannot be auto-detected. You
//   must use the /rx3 command line option to use them.  Once they have been
//   initialized with the /rx3 command they should be able to be auto-detected.
//
//
//
//   If no recognizable device is auto-detected,
//   Heather assumes that no receiver is connected and
//   defaults to a time-only mode using the system clock.
//   This will also happen if you specify the wrong com device or 
//   it is in use by another program.
//
//
//   /rxx system clock mode does not need a GPS receiver, it uses
//   the system clock to drive Lady Heather as a time display.
//   Use /rxx=17, etc to set the UTC/GPS leap second offset
//   (needed only for some of the astronomical time formats)
//
//
//   The /rx0 "gravity clock" that calculates solid earth tides and vertical
//   gravity offstes also uses the system clock to drive the program.  To 
//   use the gravity clock display, you must set your location using the 
//   /po command line or SL keyboard commands.
//
//   Also Heather likes to know your location so that the
//   sun and moon info and the astronomical time formats will work.
//   To set your lat/lon/alt use:
//      SL              - from the keyboard
//      /po=lat,lon,alt - from the command line
//
//   Heather can also get the default location from the file "heather.loc"
//   This file is read until a line is found that has a valid lat/lon/alt
//   position. The file should be saved in the heather installation
//   directory.  It is normally only used if the input device does not report
//   a location (like for rubidium oscillators, etc). It is also used if you
//   use the string "loc" when Heather requests a lat/lon/alt setiing.
//
//   The lat/lon values can either be decimal values or degrees/minutes/seconds
//   format like: 30d40m50.2s   Negative values are west longitude, southern
//   latitude.  
//
//   The altitude value is normally in meters, but can be in feet if the value
//   is followed by an "f" or "'" like  500f or 500'
//
//   In "/rxx" receiver-less mode most of the keyboard commands are 
//   meaningless (mostly the the "T" and "G" menus have relevant options)
//
//   
//   You can force the Heather display window title to an indication of the
//   receiver type with the /pt command line option.  /pt=title_string will
//   set the title to whatever you want ('_' chars are replaced with blanks).
//   /pt with no title string uses the the receiver type as the title.
//
//
//
//
//-CONFIGURING THE TIME ZONE:
//
//   You should tell Heather what time zone you are in so that the
//   proper local time can be displayed. You can set the time zone 
//   with the command line option:
//       "/tz=#sssss/ddddd" where # is the standard
//   time zone offset in hours from GMT and "sssss" is up to 5
//   characters of standard time zone ID and "ddddd"
//   is the daylight savings time zone id.  
//
//   Fractional time zone offsets can be specified 
//   like "/tz=9:30ACST".  NOTE THAT WESTERN HEMISPHERE
//   TIME ZONES ARE NEGATIVE NUMBERS! (i.e. /tz=-6CDT/CST)
//
//   The time zone ID strings can be up to 5 characters
//   long (default=LOCAL).  If no "ddddd" daylight savings
//   time zone ID is given, the program does not do
//   any daylight savings time conversions.
//
//   If a standard time zone in use,  the time shows in 
//   BLUE.  If a daylight savings time is in use, it shows
//   in CYAN.  If no local time zone is in use, it shows
//   in WHITE.
//
//   The time zone string can also be specified in the standard
//   Linux time zone format like CST6CDT (note: western
//   hemisphere time zone offset values are POSITIVE values in
//   this format)
//
//   Time zones can also be set from the keyboard with 
//   the TZ command.
//
//
//   If the user does not specify a time zone on the command line or in the
//   "heather.cfg" file, Heather attempts to get the time zone from the "TZ=" 
//   environment variable. Heather only checks the "TZ=" environment variable 
//   when starting up.  If you change it while Heather is running, the change 
//   will not be seen.
//
//
//   Many of Lady Heather's time calculations depend upon having the correct
//   "UTC offset".  This is a count of the number of leap seconds that that
//   have accumulated since the GPS system was first implemented.  It is the 
//   number of seconds of difference between GPS time and UTC time.  
//   Lady Heather normally automatically gets this value from the GPS receiver.
//   It is part of the GPS almanac data which can take over 15 minutes to 
//   arrive from the GPS satellites.  Until the UTC offset is received, 
//   Heather will display a "NO UTC OFFSET" warning.  
//
//   Some receiver data formats (like NMEA) do not provide the UTC offset
//   value. You can specify the value to use with the "/uo=" command line 
//   option. You  can also force the UTC offset value with the "/rx#=offset" 
//   command line option that sets the receiver type.  For instance with 
//   a NMEA receiver use "/rxn=18"  User specified UTC offset values are 
//   shown in YELLOW.
//
//   If no UTC offset value has been set, Heather attempts to guess an
//   approximate value.  Guessed values will be shown in RED.
//
//   Heather uses the availability of the UTC offset value from the GPS
//   receiver as an indicator that the date/time values reported are valid.
//   Until the UTC offset has been received, the date/time and other info
//   is assumed to be incorrect.  When the UTC offset value has been received,
//   the plot data queue is flushed and normal operation is started.
//
//
//   There are several special time zone names. These special time zones
//   only affect the displayed time unless you specify OT from the keyboard.
//   Note that there can be multiple names for the same special time zone.
//
//       GPS      - GPS time  
//       GPST     - GPS time  
//       UTC      - UTC time  
//       UT1      - UT1 time  
//       UT       - UT1 time  
//
//       LOR      - Loran time (9 seconds ahead of GPS)
//       LORAN    - Loran time (9 seconds ahead of GPS) 
//
//       SST/SDT  - Solar time
//       SOL      - Solar time
//       SOLAR    - Solar time
//
//       GMST     - Greenwich Mean Sidereal Time
//       GAST     - Greenwich Apparent Sidereal Time
//       LMST     - Local Mean Sidereal Time
//       LAST     - Local Apparent Sidereal Time
//
//       TAI      - TAI time (19 seconds ahead of UTC)
//       TT       - Terrestrial time
//       TDT      - same as Terrestrial time
//       TCG      - Geocentric Terrestrial Time
//       TCB      - Barycentric Coordinate Time
//       TDB      - Barycentric Dynamical Time
//       BES      - Besselian time
//       HJD      - Heliocentric Julian Date
//
//       MAR      - Mars date and time (official)
//       MARS     - Mars date and time (official)
//       MARSD    - Mars date and time (official)
//       MSD      - Mars date and time (official)
//       MTC      - Mars date and time (official)
//       AMT      - Mars date and time (official)
//
//       VEN      - Venus date and time (referenced to J1900 epoch, GPS time scale)
//       MER      - Mercury date and time (referenced to J1900 epoch, GPS time scale) 
//       PLU      - Pluto date and time (referenced to J1900 epoch, GPS time scale) 
//
//   Note that when setting one of these astronomical time
//   scales you should still specify your local time zone
//   offset (e.g.  /tz=-6LAST/LAST) so that the various
//   features (like the audible clocks and alarms) that work
//   with local time will know the correct local time.  
//   You can use the (rather obscure) OT keyboard command 
//   to cause Heather to use the displayed time for these
//   features.  See the description of the audible clocks for more details.
//
//   You can also start up in Solar Time mode with the "/bs" command line 
//   option.
//
//
//   The astronomical time scales UT1/TT/TCG/TDB/TCB/MARS,etc
//   depend upon the current utc "delta-T" value.  This
//   is normally derived +/- 0.5 seconds from the receiver
//   UTC time using the current leap second offset:
//      delta-T = UTC offset + 51.184 seconds. 
//
//   Delta-T actually changes constantly in an unpredictable manner
//   and if a more precise value is desired, you can specify it
//   with the "/uc=" command line option or TE keyboard command.
//   Heather can also read the delta-T value from the file
//   "deltat.dat". It tries to do this on startup and at
//   00:00:16 UTC every day.
//
//   If you follow the delta-T value in the TE keyboard command with an "*"
//   then the deltat.dat file will be updated with the new value.
//
//   You can set up a operating system chron job or script to fetch 
//   the current delta-T value from the net and write it to 
//   the file "deltat.dat".  On startup or at 00:00:16 UTC every day
//   Heather will try to read the current delta-T value from the file.
//
//   The special time zone name "UT1" can only be set
//   using the "-6UT1/UT1" format... the Linux format cannot
//   be used (since the "1" int "UT1" looks like a time zone offset).  
//   Use the equivalent time zone name "UT" instead.
//
//   Also supported are various planetary times: Mars ("MAR", "MSD", etc)
//   Venus ("VEN"), Mercury ("MER"), and Pluto ("PLU").  Mars time is based
//   upon the NASA definition of Mars time.  Mercury, Venus, and Pluto time
//   are based upon the number of revolutions of the planet around the sun
//   since 1 Jan 1900 (J1900).
//
//   Sorry, no time for Uranus... or Jupiter or Saturn...
//   these are big blobs of smelly gasses with no
//   fixed rotation time.
//
//   Besides specifying your time zone you should also specify your
//   Daylight Savings Time (aka Summer Time) calculation method.
//   The default daylight savings time switching dates are 
//   the US standard.  The "/b=" command line option lets you specify
//   your daylight savings time calculation.
//
//   Use "/b=1" for USA, "/b=2" for UK/Europe, "/b=3" for
//   Australia or "/b=4" for New Zealand.  "/b=0" turns off
//   daylight savings time conversions.  If you have not specified a DST zone
//   and set the DST time zone name to "BST" then zone 2 is automatically
//   set (otheriwse zone 1 is set).
//
//   If the rules change or you live in a backwater,  you can 
//   specify a custom daylight saving time rule:
//       /b=nth1,start_dow,start_month,nth2,end_dow,end_month,hour
//
//       nth1 = start DST on nth occurance of the day-of-week
//            if nth1 > 0,  count day-of-week from start of month
//            if nth1 < 0,  count from end of month
//
//       start_dow - start DST day-of-week (0=Sunday, 1=Monday, ... 6=Saturday)
//
//       start_month - 1..12 = January .. December
//
//       nth2 = end DST on nth occurance of the day-of-week
//            if nth2 > 0,  count day-of-week from start of month
//            if nth2 < 0,  count from end of month
//
//       end_dow - end DST day-of-week (0=Sunday, 1=Monday, ... 6=Saturday)
//
//       end_month - 1..12 = January..December
//
//       hour - local time hour of switchover (default = 2)
//
//     Example:  /b=-1,0,9,2,3,4,6 says to start daylight 
//               savings time on the last Sunday in September
//               and return to standard time on the second
//               Wednesday in April at 6:00 local time.
//
//
//
//
//-CONFIGURING THE UTC OFFSET (LEAPSECOND COUNT):
//
//   The difference between GPS and UTC time is known as the UTC offet.  It
//   is the number of leapseconds that has accumulated since the GPS system
//   was started.  Most GPS receivers get this from the satellites (after
//   the almanac and ephemeris data has been received).  For devices that do
//   not send a UTC offset, you can set the value with the /uo= command
//   line option:
//       /uo=seconds
//   or you can set it with the /rx## receiver type command line option
//   like:
//       /rxt=18
//
//   Furuno ESIP receivers let you store a default UTC offset value in
//   EEPROM.  This value is used until the receiver can provide the current
//   value.  The SU keyboard command lets you set the default value.
//
//   Until Heather has a UTC offset value, it is assumed that the time
//   is not valid.  If no leapseoncd value is available, Heather estimates
//   a leapsecond value to use based upon the date.
//
//   Heather shows UTC offset values obtained from the satellites in WHITE.
//   User specified UTC offsets are shown in YELLOW.  Esitmated UTC offsets
//   are shown in RED.
//   
//
//
//
//-CONFIGURING THE VIDEO SCREEN SIZE:
//
//   Lady Heather works best with a screen size of at least 1024x768 pixels.
//   This is the default screen mode.  You can specify other fixed screen
//   sizes or a custom screen size with the "/v#" command line option or 
//   via the '$' keyboard menu.  The keyboard menu also allows you to tweak 
//   the size of the text font (Tiny=8x8  Small=8x12  Medium=8x14  Large=8x16). 
//
//   Heather also now has support for an EXPERIMENTAL scaled vector font that
//   allows larger, more readable text on big screens.
//
//
//   WARNING: under Windows the F11 key is used to maximize the display 
//            true full screen mode (no title bar or edge decoration).
//            This will ONLY work if your MONITOR size is supported by 
//            old-style DirectDraw (i.e. 640x480, 800x600,1024x768,1280x1024).  
//
//            If your system does not support DirectDraw and/or your monitor 
//            size is not supported, HEATHER WILL CRASH.  If this happens, 
//            Use CTRL-ALT_DEL to bring up the Windows Task Manager and 
//            kill the heather.exe process.  If your system does support it,
//            you can start Heather in true full-screen mode with the /fu 
//            command line option. The MAXIMIZE button on the Windows title
//            bar is only enabled in "/fu" mode.  
//
//            Pressing F11 in maximized true full screen mode will restore 
//            the screen size.
//
//
//   WARNING: The macOS version of Lady Heather using XQuartz for the display
//            manager does not let you restore the window size to its previous
//            size if you maximize the window size.  You must manually resize
//            the window by dragging the lower right corner of the window.
//
//   Linux can use the F11 key to toggle to/from full screen mode.  Under
//   macOS, F11 will switch to full screen mode (but may not be able to
//   restore the previous screen size).
//
//   Screen resolutions marked ** are designed for small-ish touchscreen LCD
//   panels.  
//
//   In Linux/macOS/FreeBSD specifying these screen resolutions automatically
//   enables true fullscreen mode.  If your monitor screen size does
//   not match the selected resolution, the screen might go bonkers or
//   go to full screen mode for your monitor size. You can disable the 
//   automatic setting of full screen mode for these video modes by 
//   using "/fu /fu" commands before the /v? command.  
//
//   These modes also default to mapping all mouse buttons to the left button
//   (to get around potential bugs in the touchscreen driver). To disable this 
//   use "/mb /mb" on the command line.
//
//      /vt           - Text only Video screen
//      /vu           - Undersized (640x480) Video screen
//      /vp **        - Raspberry PI (800x480) touchscreen screen
//      /vs           - Small (800x600) Video screen
//      /vn           - Netbook (1000x540) Video screen
//      /vr **        - Reduced (1024x600) Video screen
//      /vm           - Medium (1024x768) Video screen (default)
//      /vj **        - Large (1280x800) Video screen
//      /vk           - Large (1280x960) Video screen
//      /vl           - Large (1280x1024) Video screen
//      /vv           - Very large (1440x900) Video screen
//      /vx           - eXtra large (1680x1050) Video screen
//      /vh           - Huge (1920x1080) Video screen
//      /vz           - 2048x1536 Video screen
//      /vc=colsXrows - custom screen size (e.g. /vc=1200x800)
//                      Heather supports screen widths up to 4096 pixels.
//
//      /vd **        - experimental 480x320 ultra-small screen mode
//                      (for things like Raspberry PI touchscreens).
//                      This mode uses vector fonts and the srceen formatting
//                      can be rather poor!
//
//                      Note that for several small Raspberry PI SPI interfaced
//                      touchscreens the touchscreen driver does not work
//                      well (or at all).  It ignores touches!.  You can
//                      improve this by using the /mb command line option.
//                      This maps the scroll wheel and RIGHT buttons to be
//                      the same as the LEFT button.  The touch response will
//                      be rather slow... you have to hold the touch for 2-3
//                      seconds before it will be recognized.
//
//      /ve **        - experimental 320x480 ultra-small screen mode
//                      (for things like Raspberry PI touchscreens).
//                      This mode uses vector fonts and the srceen formatting
//                      can be rather poor!
//
//      /vf           - startup in (nearly) full screen window mode - this
//                      should not be confused with true full screen mode.
//      /vq=scale     - uses a scaled vector font.  "scale" is the desired
//                      scale factor (50 to 500 percent).  This allows for
//                      better readability on large screens.
//                      Suggested values are 150 and 200 percent.
//                      VECTOR FONTS ARE CURRENTLY EXPERIMENTAL AND MAY CAUSE
//                      SOME SCREEN FORMATTING ISSUES!  They also take
//                      sligtly mode CPU power to draw.
//
//      /vi           - invert black and white on screen
//
//      /vo           - rotate image in screen window - can be useful with
//                      small LCD displays, etc.  Generally, you should 
//                      specify /vo before any /v? screen size command line
//                      option.
//                      
//
//   The "$" keyboard menu also lets you change the screen resolution.  The
//   command letters are the same as used with the "/v" commands.  Note that
//   under Windows if you select a display size that is larger than your
//   screen, Heather will down-scale the screen by dropping pixels/lines...
//   which usually looks awful.  
//
//   Changing the screen size from the keyboard may cause Heather to 
//   drop / add items from the display depending upon if it can find space 
//   to show them.
//
//   The /vu command (640x400 screen) will usually disable showing of DOP 
//   (dilution of precision) values.  Use the GX keybord command or the /gx 
//   command line option to re-enable showing the DOP values.
//
//   The "/vi" command line option and "$i" keyboard commands swap WHITE and
//   BLACK on the screen.  It looks horrible, but can be useful for doing
//   screen dumps that will be printed on paper... you remember paper, 
//   don't you?
//
//   The "G~" keyboard command lets you configure the global screen color 
//   palette. Heather uses a palette of 14 colors plus BLACK and WHITE. This
//   command lets you edit the RGB values for any of the 16 colors.  The
//   GxC keyboard command lets you assign one of the 16 colors to plot "x".
//
//   The color palette entry assigned to each of the the various plots can be 
//   changed on a plot-by-plot basis.  See the PLOTTING section for details...
//
//
//
//
//
//-CONFIGURING DATA CAPTURE SIZES:
//
//   Lady Heather records several data values from the GPS receiver into
//   a circular buffer (called the "plot queue").  Once the plot queue
//   fills up, the oldest values are replaced with the newest values.
//   The default value for the plot queue size is 3 days of data (at one 
//   second per point).  
//   
//   You can change the plot queue size with the "/q=" command line option.
//      /q=100000   - 100,000 second queue size
//      /q=2000m    - 2000 minute queue size
//      /q=300h     - 300 hour queue size
//      /q=40d      - 40 day queue size
//      /q=5w       - 5 week queue size
//
//   Each day of plot queue data (at one entry per second) uses around 15
//   megabytes of memory. Heather's basic memory usage (on Windows) is around.
//   10 megabytes. The plot queue and adev queues are the largest users of
//   of memory (in addition to the basic memory footprint).  Heather's default
//   configuration of a 3 day plot queue and 43,200 ADEV queue entries uses
//   around 90 megabytes of memory.
//      
//   Normally the plot queue is updated once a second.  You can change the
//   queue update interval with the "/i=" command line option.  For queue
//   update intervals longer than 1 second, the GPS receiver data values are 
//   averaged over the queue update interval and the averaged value is stored.
//     /i=60       - averages 60 GPS device readings and stores the result
//                   in the plot queue.
//
//   These values assume that your GPS receiver outputs data once per second.
//   If your GPS device outputs data faster than once per second (see the "!r"
//   keyboard command),  then these values must be scaled.  For instance, if 
//   your receiver is sending 10 updates per second, "/q=100000" would hold
//   10000 seconds of data and "/i=60" would update every six seconds.
//
//   If you change the queue size from the keyboard (using the "/q"
//   keyboard command) the queue data will be erased.  Changing the plot queue
//   update interval does not automatically erase the queue data, but the
//   plot time horizontal scale factor indication (like VIEW: 5 min/div) will
//   not be correct for data that was captured before the update interval was
//   changed.
//
//
//   You can clear the plot queue via the "C" keyboard menu.
//
//
//   You can disable updating of the plot queue with new data:
//      UU  - from the keyboard toggles plot queue updating
//      /u  - from the command line toggles plot queue updating
//
//      Note that if a timestamping time interval counter is in use, the
//      ADEV queues will be reset because pausing the data stream disrupts the
//      timestamp sequence which will cause the ADEV values to be corrupted.
//
//
//
//
//
//-GPS WEEK ROLLOVER ISSUES
//   
//   The GPS system does not actually broadcast a date.  It does broadcast
//   the number of weeks that have elapsed since the GPS system was first 
//   activated. However this week counter is only 1024 weeks (around 19 years)
//   long.  Once the week counter passes 1024 weeks, the date sent by the 
//   GPS receiver will be wrong (like 20 years in the past wrong).  
//
//   Modern GPS receivers attempt to get around this limitation in various ways
//   which may delay when the rollover error occurs, but it will eventually
//   happen. If Lady Heather sees a date before 2018 from the receiver, it will
//   attempt to fix it by adding 1024 weeks to the GPS date/time until the date
//   appears to be reasonable.  If Lady Heather has "fixed" the GPS date, the
//   letters "ro" appear after the date in the upper left corner of the screen
//   and the date will be shown in YELLOW.
//
//   Note that if an automatic rollover correction is applied, the time will
//   jump.  Data in the plot queue that was collected before the rollover
//   correction will have the uncorrected time stamps.  This can cause the
//   the time interval data (shown as "<interval>" in the plot header to be
//   off from the true interval.  It is recommended that if you are using a
//   receiver with known rollover issues to use the "/ro" command line option
//   to force the rollover correction befor data collection starts. 
//
//   Heather resets the plot queues if it detects a rollover fix within
//   20 seconds of starting the program.
//
//
//   You can force a rollover compensation value with the "/ro=" command line
//   option.  The rollover correction value can be either the number of 1024
//   week cycles to add to the date, or the number of SECONDS to add to 
//   the date.  You can also specify an adjustment time in 
//   weeks/days/hours/minutes/seconds by including w,d,h,m, and/or s values.
//   This feature was implemented for testing the calendar function, but
//   might have other uses.
//
//        /ro=0      - disable automatic GPS date rollover correction
//        /ro        - apply 1 1024 week rollover to the date 
//        /ro=1*     - apply 1 1024 week rollover to the date
//        /ro=2*     - apply 2 1024 week rollovers to the date
//        /ro=12345  - add 12345 seconds to the date
//        /ro=-6w4d2h30m20s - subtract 6 weeks,4 days, 2 hours, 30 mintues, 
//                     20 seconds from the date.
//
//   Two other options are available for testing calendar/DST code.  These
//   adjust the current rollover adjustment by the indicated value.  These
//   should normally only be used from the keyboard.
//        /ro-30m20s - subtract  30 mintues, 20 seconds from the current 
//                     rollover value
//        /ro+20s    - add 20 seconds to the current rollover value
//  
//
//
//
//
//-CONFIGURING FILTERS:
//
//   Many GPS receivers have options for filtering their position data in
//   various ways and optimizing them for the expected movement environment.
//
//   These command line options allow configuration of the
//   various receiver filters from the command line.  Note that not all
//   receivers support all of these filters.  These filters are also
//   usually changeable from the "F" keyboard menu.
//
//     /fa - toggle altitude filter
//     /fi - toggle ionospheric filter (Motorola)
//     /fk - toggle Kalman filter
//     /fp - toggle PV filter (position/velocity filter)
//     /fs - toggle static filter
//     /ft - toggle tropospheric filter (Motorola)
//
//           For STAR-4 receivers the FT command controls fixing timestamp
//           errors.  The STAR-4 occasionally skips a time stamp.  Setting
//           this flag will attempt to compensate for the missing timestamp,
//           but this can cause the time to actuaaly be off by one second
//           until the receiver requests satellite info at time hh:mm:33
//
//
//     /fd=# - display filter - the display filter averages # consecutive plot
//             queue values to produce a plot point.  This display filter does
//             not change the values stored in the plot queue so can be 
//             changed freely.
//
//             When you are viewing a section of the plot queue that is
//             longer than the plot area in pixels, the extra plot values are
//             generated by skipping plot queue values.  This can hide short
//             "glitches" in the data and things like the time skip, holdover,
//             and satellite changes.  The display filter helps these missing
//             values become visible (particularly using the "FD -1" setting).
//
//             If the display filter is turned on,  the values shown
//             at the mouse cursor are the filtered values.
//
//             Be careful when using large display filter values
//             with long view time displays.  It can take a lot
//             of time to process the data on slower machines.  
//
//             If the filter count is a negative value a "per-pixel" filter 
//             count is automatically determined based upon the plot view
//             interval and the plot display width.  If the "per-pixel" filter
//             is selected the calculated filter count in shown in square
//             brackets like [30].  
//             A value of -1 averages (view_interval / PLOT_WIDTH) values
//             A value of -2 averages 2*(view_interval / PLOT_WIDTH) values
//             A value of -3 averages 3*(view_interval / PLOT_WIDTH) values
//             etc...
//
//             The display filter averages the "n/2" data points each side
//             of the queue entry to create the displayed data point.  If the 
//             queue entry being averaged is less than "n/2" points from
//             the end of the captured data, the previous points in the
//             queue are averaged.  If there are less than "n" data points in
//             the queue then all the data points available are averaged.
//
//             The display filter can generate some discontinuities in the
//             plots at points within "n" points of the plot queue start
//             and end values.
//             
//
//   There are also some filter settings only changeable via keyboard commands
//   in the "F" menu.  If the receiver does not support one of these filters
//   it will not appear in the "F" menu.  The "/f" filters listed above are
//   also accessible from the "F" keyboard menu.
//
//      FC - coordinate filter
//      FE - satellite elevation mask angle - satellites below this angle
//           above the horizon will not be tracked
//      FF - foliage filter
//      FI - set ionosphere filter (Motorola receivers can do this)
//      FJ - jamming mode filter
//      FL - satellite signal level mask - satellites with signals below this 
//           setting will not be used
//      FM - movement / marine filter
//      FT - set troposphere filter (Motorola receivers can do this)
//           (or filter timestamp errors for STAR-4 receivers).
//      FX - PDOP mask / switch setting (causes receiver to switch to 2D mode
//           if PDOP is less than the specified value).
//
//   Many of the filter settings are shown in the system status column of
//   the screen display.  You can disable showing the filters:
//      GY  - toggle filter display on/off
//      /gy - toggle filter display from the command line
//
//
//      GX  - toggle the DOP (dilution of precision) value display in the 
//            receiver status information column.
//      /gx - toggle DOP display from the command line
//
//
//   The Thunderbolt GPSDO firmware smooths the output of the
//   temperature sensor with a filtering algorithm. This
//   filtering can mask and prolong the occasional single
//   point glitches that the temperature sensor produces.  Lady 
//   Heather's default action is to reverse the filtering
//   that the Thunderbolt firmware does.  
//   Removal of the temperature sensor filter makes the sensor
//   glitches much more obvious in the temperature plots and 
//   minimizes their effect in the active temperature
//   control mode.  It also makes the temperature display
//   a little less smooth since you now see the raw sensor
//   readings that have around 0.01C increments (0.16C on receivers
//   that have the newer, but lower resolution, temperature sensors).
//   The "/tj" command line option toggles the temperature sensor
//   un-filtering mode and the smoothed temperature data is used.
//
//   On Thunderbolts and other Trimble receivers you can save the filter
//   configuration into EEPROM using the "EE" keyboard command.  
//   This will write the complete current receiver configuration into EEPROM.
//
//
//
//
//
//-LOG FILES
//
//   Lady Heather can write log files of the receiver data and program status.
//   The log files can be written in real-time as the data comes in from
//   the receiver or from data saved in the plot queue.
//
//   Log files are automatically closed and re-opened once per hour.  This
//   provides some protection from data loss if your system crashes or loses
//   power.
//
//   The contents of the log files depends upon the receiver type.
//
//   Lady Heather supports several different log file formats.  The file format
//   is determined by .EXTension of the log file name:
//      .log  - a simple ASCII format log
//      .xml  - a GPX 1.1 format file that supports extended / user defined
//              data types.
//      .gpx  - a standard GPX 1.0 format file (a standardized XML file
//              oriented towards time and location data.
//      .kml  - a Google KML format location file (only stores time and 
//              lat/lon/alt)
//      .obs  - RINEX format raw observation data (pseduorange, carrier phase,
//              doppler, signal level) output of receivers that can supply this
//              data.  RINEX data can be post-proceesed to provide precise
//              locations.  See the section below on RINEX files.
//
//   Note that .gpx / .xml / .kml / .obsfiles are larger than the .log ASCII
//   files.  The .xml (GPX 1.1) log format contains the most comprehensive 
//   data including pretty much the complete receiver configuration.
//
//
//   To start logging data from the keyboard:
//      WLW or LW - write a new log file from real-time data
//      WLA or LA - append real-time data to a log file
//      WLS or LS - stop logging real-time data
//      WLH or LH - write a new log file from real-time data in formatted 
//                  HEX/ASCII packet format 
//
//   From the command line:
//      /w=file   - set log file name to Write to
//      /wa=file  - set log file name to Append to
//
//      /wh       - toggles writimg the log file as a formatted  HEX/ASCII
//                  packet log file instead of a data log.
//
//
//   You can also write RINEX files as a separate file.  This allows you to
//   write a standard log file and a RINEX file at the same time:
//      MW - write a separate RINEX file  (from the keyboard).
//      /mw=file  - set RINEX file name to write to (from the command line)
//
//   If you add an "*" to the end of the log file name, the log file write
//   buffer is flushed to disk on every write.  If log flush mode is enabled
//   the "Log:" file name indicator is shown as "LOG:"  If the log file is
//   already open then the /wq command line option will toggle log flush mode.
//
//
//   You can also write a file of tracked satellite time, PRN, azimuth,
//   elevation, and signal level data:
//      WLP or LP - write a sat .prn log file from real-time data.
//
//   If you add an "*" to the end of the PRN file name, the prn log file write
//   buffer is flushed to disk on every write.  If prn flush mode is enabled
//   the "Prn:" file name indicator is shown as "PRN:" 
//
//
//   You can write a log file from data in the plot queue:
//      WA  - writes ALL data in the plot queue to a log file
//      WP  - writes the data from the area of the plot queue that is 
//            being displayed on the screen.
//
//            Note that the *tow* time-of-week field in logs generated from 
//            queue data is not the official GPS time-of-week,  but is just 
//            a sequential number.
//
//            If writing the plot window queue data to a log file
//            AND the plot queue is full and warping AND the queue
//            updates are not paused AND the plot window covers
//            all of the queue data,  then there may be a glitch
//            at the beginning of the log output file.  Several
//            seconds of the latest data can appear at the start 
//            of the log data.
//
//            You cannot write a RINEX file from plot queue data.
//
//
//   You can delete files:
//      WD  - deletes a file
//
//
//   Normally Heather updates the log file every second (or every time a 
//   new receiver data point come in).  You can configure the log update
//   interval.
//      WLI or LI     - set the log update interval  -or-
//      /l[=seconds]  - from the command line
//
//
//   Normally Heather does not write the satellite constellation data (sat
//   PRN, azimuth, elevation, signal level) to the log file.  You can enable
//   logging of the satellite constellation data:
//      WLC or LC - toggle logging of satellite constellation data
//      /ld       - from the command line
//                  Note that the sun is logged as satellite PRN 1000 and 
//                  the moon as PRN 1001.  (WAS 256 AND 257 IN PREVIOUS
//                  RELEASES)
//
//
//   Normally Heather writes unfiltered data to log files.  If the display
//   filter is enabled (FD keyboard command) you can toggle the writing of
//   filtered data to the log file:
//      WF  - toggle writing of filtered data to the log file.
//
//
//   Normally Heather waits for any receiver id information before writing
//   data values to log files. You can configure heather to write log data
//   brfore the receiver id information has arrived.
//   This command can be useful if Heather thinks that a receiver should be
//   sending id information, but the receiver has non-standard firmware that
//   does not send id information.
//      /li - from the command line - toggles the "log id wait" flag.
//
//
//   Besides data logs, Heather also supports writing a debug log file:
//      WX  - write debug log file  -or-
//      /dl[=file]  - from the command line (if a file name is not given
//                    "debug.log" is used.
//      The content of the debug log is device dependent and subject to
//      change.
//
//
//   Heather also supports writing a receiver data capture file:
//      WY          - write receiver data capture file from the keyboard
//      /dr[=file]  - from the command line (if a file name is not given
//                    "heather.raw" is used.)
//
//      If you add a '*' to the end of the data capture file name, then the
//      data is flushed to disk every byte (default is to let the OS write the
//      data to disk whenever its internal buffer is full.  Flushing to disk
//      every byte is OS resource intensive but helps make sure all data
//      has been written to disk if an unexpected program crash occurs.
//      In raw flush mode the "Cap:" log file name is shown as "CAP:".
//     
//
//
//   If a time interval counter is being used Heather also supports writing 
//   a raw counter data capture file:
//      WT          - write counter data log file from the keyboard
//      /dq[=file]  - from the command line (if a file name is not given
//                    "ticc.raw" is used.)
//
//
//   In ASCII format logs, the data separator can be changed from a TAB to
//   a comma with the command line option:
//      /ls   - toggle log file value separator between TABs and COMMAs
//      /ls=c - set separator char to "c".
//
//
//   You can disable comments in log files from with the command line option:
//      /lc  - toggle writing any comments to the log file
//             Note that disabling log comments means Heather cannot
//             calculate the date of a log entry or the log data interval
//             because these values are stored as special comments.
//
//             ALSO: to read a log file that was written without comments, 
//             the /lc command must be in effect,  otherwise the file will not 
//             be recognized as a log file because Heather uses the "#" comment
//             line on the first line of the file to help it recognize the
//             file is a potential log file.  XML/GPX logs don't have this 
//             limitation.
// 
//
//
//   You can disable logging of detected errors with:
//      /e   - toggle logging of detected errors in the log file
//
//
//   Lady Heather can read in log files and show the data in the plot area.
//   Reading in a log file first pauses the plot queue updates from live 
//   incoming data.  The current plot queue data is cleared out unless
//   you preceed the file name with a '+' to append the log data to the
//   current data. You can then scroll around the the log file data 
//   using the normal plot viewing commands.  You can resume processing
//   of receiver data using the "U" keyboard command... you might want
//   to first clear the plot queue data ("C" keyboard menu).  RINEX files
//   cannot be read in.
//  
//      R       - read a file (with .log .xml .gpx file extension)
//      /r=file - from the command line
//
//                Note that If you  read in a log file, Heather should first
//                be configured ("/rx#" command line option) for the receiver 
//                type that created the log file. 
//
//                Note that only one log file can be read using the "/r="
//                command line option.  You cannot use multiple /r= options
//                to read and append multiple log files.
//
//
//
//   Log files can be automatically written on a scheduled basis.  See the
//   section on SCHEDULED EVENTS for details.
//
//
//
//
//-RINEX files
//
//   Some receivers can supply "raw" data observations from the GPS satellites
//   (not to be confused with Heather's "raw receiver data capture files" which
//    record all data sent from the receiver to a file).
//   Raw observation data includes pseudoranges, carrier phase data, doppler, 
//   and signal levels.  Heather can write this data to a RINEX format 
//   observation file.  RINEX is an insustry standard file format used to 
//   transfer raw data observations to post-processing services to get a 
//   precise location.
//
//   Currently supported receivers that can supply "raw" observations include:
//      Ashtech Z12 (L1 and L2 observations)
//      Furuno ESIP receivers  (if baud rate is >= 115200 baud).
//      Motorola Oncore VPZ receiver (with raw measurement data firmware)
//      NVS-08 receiver
//      Ublox timing receivers
//      Most Trimble TSIP receivers and GPSDOs (SV6 does not work).
//      Trimble RT17 format receivers like the NetRS
//      Venus/Navspark RTK capable receivers
//
//      The ESIP and TSIP receivers output only pseudorange, doppler, and
//      signal level observations.
//
//      The Trimble telecom GPSDOs (NTBW,NTPX,NTGS,etc) can produce rather
//      noisy results and may not yield a usable solution.  This may be
//      related to their tendency to cause data jumps when satellites enter
//      and leave the tracked constellation.  Increasing the satellite
//      elevation and/or signal level filters may help... but settings that
//      are too high can cause less than 4 satellites to be tracked... which
//      is a bad thing...  (Update: recent changes to Heather has greatly
//      improved the resuluts with these receivers).
//
//      The Trimble receivers can take around 30 seconds before all satellite
//      ephemeris data has been collected and is available for generating
//      RINEX files.  The original Resolution-T takes around 90 seconds to
//      gather all the ephemeris data.  Also this reveiver requires thet the
//      RINEX data rate be set to 3 seconds.  Note that since CSRS-PPP updated
//      their processing system, performance with Trimble receivers was
//      greatly reduced!!!  Typically over 50% of observations are rejected.
//
//      The Ashtech Z12 receiver gets its time display from the system clock.
//      It also uses the system clock for determining the GPS week number
//      rollover correction value.  If the system clock is not accurate you
//      should avoid collecting data that includes the GPS week number change
//      (00:00 GPS time on Sunday).  This can cause a glitch in the calculated
//      observation timestamps and most RINEX processing services will reject
//      the file.
//
//      You can verify that the receiver can generate a RINEX file by clicking
//      on the satellite information table.  If you see a PSEUDORANGE or
//      CARRIER column, you shouild be able to generate a RINEX file.
//
//   Before a RINEX file will be written, the receiver must have a valid time
//   and UTC offset value.
//
//   A lot of receivers seem to have a problem with their raw data observations
//   around the time of the GPS week rollover (00:00 UTC on Sunday).  It is
//   best to not collect data that spans this time.
//
//   For best results the receiver should be in position hold mode with a 
//   self-surveyed or reasonably accurate position, but this is just a 
//   suggestion.
//
//   Note that there can be a LOT of raw data.  You will probably need to
//   configure the receiver to a high baud rate to prevent over-running the
//   receiver transmit buffer.  Heather now has the "!x" and MX keyboard
//   commands for setting the receiver baud rate for devices that support raw
//   data.  IF YOU SET THE RECEIVER TO A NON-DEFAULT VALUE YOU WILL NEED TO
//   SPECIFY THE BAUD RATE ON THE COMMAND LINE (/br=...) WHENEVER YOU START
//   HEATHER.  If the receiver type can be auto-detected and the baud rate is
//   one of the supported auto-detect rates (9600,19200,38400,57600,115200
//   baud) then you may not need to force the baud rate setting.
//
//   You can write the RINEX file using log file commands and specify an
//   file name extension of .obs or you can write the RINEX file as a separate
//   file (this allows you to write a normal log file and a RINEX file at
//   the same time.  See the section above on the commands used to enable
//   RINEX format files.  Update: Writing RINEX files as a log file is now 
//   deprecated and should not be used.  
//
//   The receiver should be configured for a navigation message output rate
//   of one Hz (!r command).  Heather does have some code for working
//   with receivers that are outputing position data at faster rates... but
//   it is a bit wonky and may not work properly in all cases.  Also many
//   receivers seem to mess up / skip raw data messages at faster nav rates.
//
//
//   Heather has several commands for configuring RINEX files.  You should NOT
//   use any of these commands while a RINEX file is being written.
//
//     /rr=secs -  sets the receiver raw data mesage output rate (in seconds).
//                 RINEX files can be very large.  The /rr command lets you
//                 specify the raw data observation rate.  Faster rates can
//                 produce more accurate results, but generally rates of
//                 10-30 seconds are about as good as faster rates.  Heather
//                 does not currentlt support fractional second raw message 
//                 rates or rates faster than 1Hz.
//      MR         - from the keyboard
//
//                 For the Ublox M8N receiver, a negative value for raw rate
//                 enables the undocumented TRK_MEAS and TRK_SRFBX messages.
//                 These messages are only available for M8N receivers with
//                 early versions of the firmware.  Heather does not parse
//                 them, but the messages will be written to the reciver "raw"
//                 data capture file (WY command) if it is enabled.  RTKLIB 
//                 can be used to process the capture file into a RINEX file
//                 (don't confuse receiver raw data capture files with RINEX
//                 obervattion "raw" measurements / RINEX files).
//
//                 The original Trimble Resolution-T receiver has firmware
//                 issues that cause it to only be able to output RINEX data
//                 every 3 seconds.  Normally Heather does not enable the
//                 raw data for this receiver, but if you set the raw rate
//                 to 3 seconds, it will do it... but the clock will only tick
//                 every 3 seconds. Setting the rate < 3 seconds  disables 
//                 raw data.  Setting values over 3 seconds will use 3 seconds.
//
//                 For all all the Trimble receivers you should click on the
//                 satellite information table and verify that the receiver
//                 is showing PSEDORANGE data for all tracked satelliites
//                 before starting to write a RINEX file.  This usually 
//                 takes around 30 seconds or less.
//
//                 Some receivers only output observations at 1 Hz.  For
//                 thse receivers, when you set the raw rate to other than 
//                 1 Hz,  Heather drops unwanted observations by calculating
//                 (GPS time-of-week mod raw_message rate).  You must specify
//                 a raw message rate that divides evenly into 604800.
//
//
//      /mw=name   - from the command line (this is not recommended because
//                   not all satellite information may be available before
//                   the file starts writing)
//      MW         - from the keyboard - opens/closes the RINEX file to write.
//
//
//      MX         - from the keyboard - sets the receiver baud rate.
//                 See the warning above about the implications of setting
//                 the receiver baud rate to its non-default value.
//
//      MI         - set bad observation data fixup mode (default is enabled).  
//                 If enabled, Heather attempts to fix potential errors in 
//                 the RINEX data.  Values that are "stuck" and not changing 
//                 are blanked.  Duplicate observation time stamps are deleted,  
//                 missing observations are replaced with null records, etc.
//
//
//      /at=antenna - sets the antenna type to include in the RINEX file.
//                 Many survey grade antennas have precisely measured 
//                 characteristics (like their phase center) and if these
//                 are known they can be used to improve the post-processing
//                 results.  Most post-processing services have a library
//                 of these antenna types which can be selected using an
//                 antenna type code.  The /at or MA commands lets you specify
//                 the antenna type code.  Or, you can manually edit the
//                 RINEX file to include the proper antenna type code.
//                 Any '_' in the antenna name are replaced with a ' '. If
//                 the offical antenna name has an '_' in it, you will need
//                 to manually edit the RINEX file antenna number/type record
//                 in the file header.
//      MA         - from the keyboard  (the MA command does not have any
//                   limittations on '_' or ' ' in the antenna name).
//
//
//      /ah=antenna_height - Lets you specify the height of the antenna above
//                 the ground.  If you don't specify an antenna height, the
//                 post processing services will calculate the location of
//                 the antenna (which is what you probably want if you
//                 are configuring a timing receiver).  If you specify the
//                 antenna height then the services will return the location
//                 of the point on the ground directly below the antenna.
//                 Besides the antenna height displacement you can also set
//                 the east-west and north-south displacements:
//      /ah=height,ew,ns - sets the antenna height and east-west and
//                 north/south displacements (in meters).
//      MH         - from the keyboard
//
//
//
//   The following antenna and marker commands provide descriptive information
//   to be included in the RINEX file.  This information is optional and does 
//   not alter the the location results.
//
//      /an=number - sets the antenna number to include in the RINEX file.
//                The number can be alphanumeric.
//      MU         - from the keyboard
//
//
//
//      /ak=marker - sets the marker name
//      MK         - from the keyboard
//                 If a marker name is not given, Heather creates one from
//                 the receiver type (and a string of characters that
//                 represent the satellite systems that are being used (if
//                 available and the receiver supports multiple GNSS systems).
//
//      /av=marker - sets the marker number
//      MV         - from the keyboard
//
//
//
//
//      /rm=raw_meaurements - Heather defaults to including all available
//                 raw measurements in the RINEX file.  The /rm command
//                 lets you control which measurements that you want to
//                 include in the RINEX file (and also the order they are
//                 written in.  The /rm command is used for RINEX v2.11 files.
//                 RINEX v3.xx has separate observaion lists for each satellite
//                 system and uses different (3 character) measurement type
//                 codes.
//
//                 Supported v2.11 measurments are:
//                    C1 - C/A code pseudorange
//                    L1 - L1 pseudorange
//                    L2 - L2 pseudorange
//                    L5 - L5 pseudorange (GPS/GLONASS/GALILEO)
//                    L6 - L6 pseudorange (Galileo)            
//                    L7 - L7 pseudorange (Galileo)            
//                    L8 - L8 pseudorange (Galileo)            
//
//                    P1 - L1 carrier phase
//                    P2 - L2 carrier phase
//                    P5 - L5 carrier phase (GPS/GLONASS/GALILEO)
//                    P6 - L6 carrier phase (Galileo)            
//                    P7 - L7 carrier phase (Galileo)            
//                    P8 - L8 carrier phase (Galileo)            
//
//                    D1 - L1 doppler
//                    D2 - L2 doppler
//                    D5 - L5 doppler (GPS/GLONASS/GALILEO)
//                    D6 - L6 doppler (Galileo)            
//                    D7 - L7 doppler (Galileo)            
//                    D8 - L8 doppler (Galileo)            
//
//                    S1 - L1 signal level
//                    S2 - L2 signal level
//                    S5 - L5 signal level (GPS/GLONASS/GALILEO)
//                    S6 - L6 signal level (Galileo)
//                    S7 - L7 signal level (Galileo)
//                    S8 - L8 signal level (Galileo)
//                  Note: Heather curently does not support any receivers
//                  with L5/L6/L7/L8 signals.
//
//         /rm       - limits measurements to the L1 data
//         /rm=list  - 'list' is a comma separated list of the measurement
//                     types to include like:
//                     /rm=C1,D1 - put only C1 and D1 data in the RINEX file
//         MM        - from the keyboard
//
//   For RINEX v3.xx the various GNSS satellite systems have separate
//   independent observation lists.  You can set the observation types to 
//   be used for each system:
//         /rmb=list - BEIDOU
//         MB        - from the keyboard
//         /rmg=list - GPS
//         MG          from the keyboard
//         /rmn=list - GLONASS
//         MN          from the keyboard
//         /rml=list - GALILEO
//         ML        - from the keyboard
//         /rms=list - SBAS
//         MS          from the keyboard
//
//   Heather normally writes a RINEX v2.11 format file.  There is also
//   support (currently incomplete) for writing v3.xx files.  You can select
//   the RINEX format with the /rf command line option.  Note that none of
//   the standard online post-processing services seems to accept RINEX v3.xx
//   files.
//      /rf         - toggle between v2.12 and v3.03
//      /rf=version - set specific version type.
//      MF          - set RINEX version from the keyboard
//      
//   Heather includes raw measurement data from all the satellites that it
//   sees.  If the receiver supports multiple satellite systems (GPS/SBAS/
//   GLONASS/GALILEO) and you want to exclude a particular satellite system's
//   data from the RINEX file use the SG keyboard command to disable tracking
//   that system.
//
//   Another way to get RINEX files from Lady Heather is to write a raw
//   receiver data capture file (WX command) and use a program like RTKLIB 
//   or TEQC to process the raw receiver data capture file into a RINEX file.
//
//   Once you have a RINEX file you will need to process it to get precise
//   position data.  The easiest way to do this is to submit it to an
//   online processing service.  There are several free services available
//   but most only accept data from dual frequency (L1/L2) receivers.  You
//   should probaly .ZIP the file before submitting it since they can be
//   very large.  AUSPOS does not accept .ZIPed files.
//
//   The CSRS-PPP service from NRCAN (Natural Resouces Canada) can handle
//   L1 only data.  Also, they probably have the best output reports. They
//   are the currently recommended processing service and the only one
//   that currently handles L1 only data.  Their results are available
//   2-3 hours after the last record in the file was writen.  If the file 
//   contains GLONASS data it can take a bit longer for them to get the 
//   GLONASS orbits.  If you  submit a file before the GLONASS orbits are 
//   available, they will process the GPS data and send a report.  Later 
//   they will send another report with the GPS and GLONASS data.  NOTE:
//   for L1 only receivers, CSRS-PPP currently seems to only process the 
//   pseudorange data!!!  Carrier phase and dopper measurements are
//   ignored!!!   CSRS-PPP's current (upgraded?) processing system does
//   NOT work well with Trimble receivers... typically over 50% of the
//   observations are rejected!
//
//   AUSPOS in Australia seems to report the smallest error ellipse sizes,
//   but the actual positions seem to differ from the results of other
//   processing services (perhaps due to the long base-lines to the referecnce
//   stations that they use). Note that you have to wait 24 hours after the
//   RINEX file was written before submitting the file.  AUSPOS does not
//   seem to like .ZIPed files.  They do support FTP uploads.
//
//   OPUS in the United States seems to be VERY finicky about the input files.
//   They seem to reject a lot of files that CSRS-PPP and AUSPOS have no
//   problem with.  Note that if you use a Z12 receiver, OPUS does not work
//   with the Z12's default 20 second raw data rate.  You will need to use
//   the /rr= or MR command to set the raw data message interval to something 
//   it can use.  OPUS does not work with L1 only data.  Although OPUS says
//   they can process files up to 48 hours long, but those 48 hours can only
//   span two calendar days. So, if you start a 48 hour run in the middle of
//   the day, OPUS will not process the data... bastards!
//
//   Also note that all the post processing services have VERY poor error
//   reporting if something goes wrong.  The typical error message is along
//   the lines of "Error in file" with very little hint as to what or where
//   the error is.
//
//   The post-processing services use precise satellite orbit measurements,
//   etc to massage the receiver RINEX data to get precise locations.  There
//   are three main types of orbit data that they use:
//      Ultra-rapid - based upon current and predicted measurements of the
//                    satellite orbits.  The ultra-rapid results are the
//                    least accurate, but still are pretty good.  Typical
//                    results may be a few centimeters worse than the
//                    more precise orbits.
//      Rapid       - The rapid orbits are based upon data from worldwide
//                    monitoring stations.  They are available around 24
//                    hours after the RINEX file was written.  
//      Precise     - the precise orbits are available 1-2 weeks after the
//                    RINEX file was written.  They give the most accurate
//                    results (but usually not significantly better than
//                    the rapid orbits).
//
//   Note that some receivers (like the Furuno ESIP receivers) report/want
//   altitude as "Orthometric" height / height above geoid.  Most receivers
//   use GPS (geoid) altitude If you are using the post-processing results 
//   to set your receiver's position hold location, make sure that you use 
//   the correct altitude value (WGS84 geoid or Orthometric).  
//   Also, different receivers may use different geoid models than the 
//   post-processing service to get ortometric altitudes.  This can lead to 
//   reduced accuracy.  Consult your receiver manual to find out if it uses
//   GPS or othometric altitude... hopeully they bother to tell you which one
//   they use... but don't count on it!  At my location the GPS and
//   orthometric altitudes differ by around 25 meters so using the correct
//   altiude that the receiver expects is important.
//
//
//
//
//-TIME DISPLAYS 
//
//   Lady Heather has three main time displays:
//      1) The date/time block in the upper left hand corner of the screen
//      2) A digital clock display
//      3) An analog watch display.
//
//
//   The date/time block is always shown. It contains the time / time zone, 
//   the date,  the GPS week number,  the GPS time-of-week, and the "UTC offset"
//   leap second count.  It also indicates whether the GPS receiver is running
//   in GPS time mode or UTC time mode and the validity of the receiver time.
//
//   If the receiver does not report the GPS week or time-of-week then
//   Heather will derive these values from the time and both the WEEK: and 
//   TOW: values will be shown in YELLOW (instead of WHITE).
//
//   If a GPS week rollover condition has been detected and is being
//   compensated for, the date is shown in YELLOW and is followed by " ro".
//
//   The time in the time block is normally shown if BLUE if daylight savings
//   time is not being applied,  CYAN if daylight savings time is in effect,
//
//   The time can be shown in a few different formats:
//     /tp  - shows time as fraction of a day
//     /tq  - shows time as total seconds of the day
//
//
//
//   The digital clock display is located between the satellite information
//   data and the plot area,  It is normally CYAN in color.  If the GPS
//   receiver reports invalid time, it shows in RED.  If no UTC leapsecond
//   offset is available, it shows in YELLOW.
//
//      GZ  - from the keyboard toggles the digital clock on/off
//      /gz - from the command line
//
//   Clicking on the digital clock display (or just under the satellite 
//   information display) will zoom the digital clock display to full screen.
//   Cicking again will restore the screen to its previous state.
//   Note that short clicks might be ignored... particularly on devices like
//   UCCM receivers that only output time updates every two seconds.  It can
//   help to hold down the mouse button until the screen changes.
//
//
//   You can control the format of the digital clock:
//      TM   - toggles between a seconds resolution clock or a millisecond clock
//      /tsz - from the command line
//
//      TW   - toggles between a 24 hour clock and a 12 hour AM/PM clock
//      /ti  - from the command line
//
//      TJ   - toggles between a Julian date.time clock and a normal clock
//      /tsj - from the command line
//
//      TQ   - toggles between a Modified Julian date.time and normal clock
//      /tsk - from the command line
//
//      TN   - normal 24 hours seconds clock
//      /tsn - from the command line
//
//      /tsu - display time in Unix epoch seconds.
//             This time is adjusted for the currently set local time zone.
//             For actual Unix time, set the time zone offset to 0.
//
//      /tsg - display time in GPS epoch seconds.
//             This time is adjusted for the currently set local time zone.
//             For actual GPS time, set the time zone offset to 0.
//
//      TI   - time interval (stopwatch)
//      /tsw - from the command line
//
//             This toggles the digital clock display between the last selected
//             clock format and the number of seconds between the current time
//             and the time the last clock format command was issued (or the
//             time Heather was started up if no clock format command was
//             ever set).  So, to reset and stop the "stopwatch", issue a time
//             format command (such as TN). Then you can issue the TI command
//             to restart the stopwatch.
//      
//
//
//   The watch display is located either in the upper right hand corner of
//   the screen or to the right of the plot area.  The watch outline is
//   normally shown in BLUE or CYAN.  It is drawn in RED if the GPS reports 
//   that the time is not valid,  and in YELLOW if no UTC leapsecond offset 
//   is available.
//
//      GW  - from the keyboard toggles the watch on/off
//      /gw - from the command line
//
//   Clicking on the watch display on the screen will zoom it to full 
//   screen.  Clicking again will restore the screen to its previous state.
//   Note that short clicks might be ignored... particularly on devices like
//   UCCM receivers that only output time updates every two seconds.  It can
//   help to hold down the mouse button until the screen changes.
//
//
//   You can label the watch face with a "brand name".  On small screens there
//   might not be room to show the brand name:
//      /tb      - toggles labeling of the watch face
//      /tb=name - sets a brand name on the watch face. Any "_" in the brand
//                 name is converted into a space.  The brand name can be two
//                 lines long.  Separate the lines with a "/".  A two line 
//                 watch name does not show the date in the clock face.
//      /tb=     - sets the watch "brand name" to the day of the week.
//                 This is the default setting.
//
//
//   You can specify the watch face style with the /wf= command line option
//     /wf=0  - normal Roman numeral clock
//     /wf=1  - decimal hours clock
//     /wf=2  - "*" hour markers
//     /wf=3  - 24-hour Roman numeral clock
//     /wf=4  - 24-hour decimal hours clock
//     /wf=5  - 24-hours "*" hour markers
//
//     /wt    - straight shaped hour/minute hands
//     /wt=0  - straight shaped hour/minute hands
//     /wt=1  - filled trapazoidal shaped hour/minute hands (default)
//     /wt=2  - hollow trapazoidal shaped hour/minute hands
//        
//
//
//   The watch display includes a representation of the moon at its current
//   location in the sky and with its current phase.  The moon is shown in
//   YELLOW if it is visible and GREY if it is below the horizon.  The sun
//   is shown as a filled in yellow circle with "rays" if it above the horizon 
//   and as an empty yellow circle with rays if it below the horizon.  
//   The watch display also flags when the moon is new, quarter, or full.  
//   Also "blue" and "black" moons are shown.
//
//   You can disable the sun/moon images in the satellite map and watch
//   displays using the command line options:
//      /kj   - toggle sun/moon drawing
//      /kj=0 - disable sun/moon drawing
//      /kj=1 - disable sun drawing
//      /kj=2 - disable moon drawing
//      /kj=3 - disable sun and moon drawing
//   
//
//   Note that the watch display is not updated while a keyboard command
//   menu is being displayed and the "GB" option is in effect that allows
//   maps and/or the watch to be displayed in the plot area.
//
//
//   The ZC keyboard command will zoom the clock display to full screen.
//
//   The ZW keyboard command will zoom the watch display to full screen.
//      Clicking the mouse will toggle between the zoomed watch and digital 
//      clock displays. 
//      Clicking in the upper left hand corner of the screen will restore
//      the screen to normal mode.
//      Note that short clicks might be ignored... particularly on devices
//      like UCCM receivers that only output time updates every two seconds.
//      It can help to hold down the mouse button until the screen changes.
//
//   The ZB keyboard command will zoom the watch and satellite map displays 
//   to full screen overlayed on each other.
//      Clicking the mouse will switch to the ZV display where you can then
//      click again to select another display to zoom to full screen.
//      Clicking in the upper left hand corner of the screen will restore
//      the screen to normal mode.
//      Note that short clicks might be ignored... particularly on devices
//      like UCCM receivers that only output time updates every two seconds.
//      It can help to hold down the mouse button until the screen changes.
//
//
//   Note that the watch or clock do not have to be enabled on the main
//   screen for the zoomed displays to work.  Pressing any key (except '\') 
//   will restore the main display screen if it has been zoomed. '\' will
//   dump a .GIF image of the zoomed screen to the file "xxxx.gif" where xxxx
//   is the receiver type (if you press SPACE to bring up the keyboard help
//   screen, the file name used will show up by the '\' entry).
//
//   You can also force a screen dump by left-clicking on the screen where
//   the "Receiver data" info is near the upper left hand corner of the
//   screen.  This is handy if you are using a touch-screen.
//
//
//   The "/ta" toggle command line option shows dates in the European
//             the European dd.mm.yyyy format instead of the normal 12 Oct 2016
//             format. 
//
//   The "/tl" toggle command line option shows dates in the ISO
//             yyyy.mm.dd format instead of the normal 12 Oct 2016
//             format. 
//
//
//
//
//
//--PENDING LEAPSECOND DISPLAY
//
//   Many GPS devices report when a leapsecond adjustment has been announced.
//   Heather shows this in the receiver status column. Leapsecond
//   announcements are generally made 6 months in advance.  
//
//      If the receiver supports leapsecond announcements but no leapsecond
//      is pending it shows "No leap pend" in GREEN.  If a leapsecond 
//      adjustment has been announced it shows "Leap pending" in YELLOW.  
//
//      Many receivers send enough enough information to determine the date of
//      the leapsecond event.  If this information is available the leapsecond
//      status shows a countdown clock like "Leap 45 days".  If the receiver
//      does not report the exact date of the leapsecond, Heather assumes it
//      will be on the last day of June or December and indicates this guess
//      by "Leap 45 days?".
//
//      As the time of the leapsecond nears, the countdown clock starts showing
//      hours, then minutes, then seconds until the leapsecond.  When showing 
//      hours, any fractional hour count is rounded up,  so the countdown
//      clock will show 2 hours then 59 minutes.
//
//      Some receivers (like the Z3801A and Z3812A have firmware bugs that 
//      expect a leapsecond announcement no more than 3 months in advance.
//      These receivers will display an invalid leapsecond date while the
//      pending leapsecond is more than three months in the future and may
//      take several days to figure out the proper leapsecond date once the
//      erroneous date has passed.
//
//
//
//
//
//
//--DATE AND CALENDAR DISPLAYS 
//
//   Lady Heather can display the date in various calendar formats. The
//   calendar type is selected by a command line option:
//      /d  - default Gregorian calendar
//      /da - Afghan calendar
//      /db - Mayan Haab calendar
//      /dc - Chinese calendar
//      /dd - Druid calendar
//      /dh - Hebrew calendar
//      /di - Islamic calendar
//      /dj - Julian date
//      /dk - Kurdish calendar
//      /dm - Modified Julian Date (MJD)
//      /di - Indian civil calendar
//      /dp - Persian calendar
//      /ds - ISO date (yyyy-day_of_year)
//      /dt - Tzolkin calendar
//      /dv - Bolivian calendar
//      /dw - ISO week format (yyyyWww-dow)
//      /dx - Xiuhpohualli (Aztec Haab) calendar
//      /dy - Mayan calendar
//      /dz - Aztec Tonalpohualli calendar
//      /dyyyymmdd - force date to year yyyy, month mm, day dd for testing
//                   (use a leading zero for months/days less than 10)
//
//   For several of the calendars you can specify an epoch correction factor
//   for the date calculations.  The correction factor is the number of days
//   (+ or -) to add to the default date calculation.  This is to compensate
//   for various interpretations of when the calendar should begin.
//
//      /db=days   -  AZTEC_HAAB
//      /dc=days   -  CHINESE
//      /dd=days   -  DRUID
//      /dt=days   -  TZOLKIN
//      /dv=days   -  Bolivian
//      /dx=days   -  Xiuhpohualli
//      /dy=days   -  MAYAN
//      /dz=days   -  AZTEC Tonalpohualli 
//
//
//   Heather has a "greetings" calendar function.  This displays a message
//   at the bottom of the plot area whenever a special event or day occurs.
//   The greetings calendar is read from the file "heather.cal".  If no
//   calendar file is seen, Heather uses an default internal calendar file.
//
//   In addition to displaying a greeting, you can specify a time to sound
//   the alarm on the day of a greeting.
//
//
//   You can disable the greeting calendar with:
//      /gn  - toggles the greetings calendar from the command line
//
//
//   The calendar file should be placed in the same directory as the 
//   "heather.cfg" file.  The proper directory is shown when you do a 
//   "HEATHER /?" command line or enter ? from the keyboard.
//
//   When a calendar file date is matched to the current date, the message is 
//   displayed at the bottom  of the plot window until erased (G G command) 
//   or the start of the next day.  Up to 5 calendar match entries can be
//   shown for one day.
//    
//   Fields on each line in "heather.cal" are:
//      nth   - event happens on the n'th occurance of DAY in the month
//              (negative values are from the end of the month)
//              (positive values are from the start of the month)
//              (zero means the event occurs on a fixed day number)
//              Values >= 100 are codes for holidays that must be specially
//              calculated.
//
//      day   - The DAY of the month if nth is 0
//              The DAY of the week if n'th is not zero
//              (0=Sunday,  1=Monday,  ...  6=Saturday)
//
//      month - (1=January ... 12=December  0=ignore this entry)
//
//              If DAY < 0 then MONTH is the day-of week code.
//              This allows for doing days like Friday the 13th (0, -13, 5)
//
//
//      text  - The text to display when the event occurs.  If the text begins
//              with "@hh:mm:ss" this will set the alarm to sound at the
//              specified time on the day of the alarm. For example a calendar
//              file enrty of:
//                 0 1 1 @00:00:00 Happy New Year
//              will sound the alarm at midnight on New Year's Day.
//
//              Note that if an alarm is alreay set, the calendar alarm will
//              not override it.
//
//   Comment lines can start with # * / or ; in column 1
//
//
//
//
//
//-AUDIBLE CLOCKS, ALARMS, and SCHEDULED EVENTS
//
//   Lady Heather has several audible clock modes that signal the time via
//   the computer's sound system.
//
//   The singing clock:
//     The singing clock signals the time by playing .WAV files at fixed
//     intervals throughout the hour.  It is activated via:
//        TH #S   - from the keyboard
//        /th=#s  - from the command line
//
//     The number (#) is the number of times per hour to play the files.
//     For instance /th=4s says to play a sound file 4 times per hour (every
//     15 minutes).   The files to play should be placed in the default
//     heather directory are named:
//        "heather_songxx.wav"  where xx indicates the minutes.
//
//     if # is 0 or not given, the singing clock is disabled.
//
//     If the singing clock is activated a double musical note symbol is
//     shown near the upper left hand corner of the screen.
//
//     At 1 second past midnight on New Years, the file "heather_new_year.wav"
//     will be played (if it exists in the current installation directory).
//
//
//   Westminster Chime (Big Ben) mode:
//       TH 4W   - from the keyboard
//      //th=4w  - from the command line
//
//      This mode is very similar to the singing clock, except on the hour
//      the file played is "heather_hourxx.wav"  NOTE THAT THE LADY HEATHER
//      DISTRIBUTION DOES NOT INCLUDE THE NEEDED .wav files.  To implement a
//      proper Big Ben clock, you would need twelve .wav hour files:
//      (heather_hour00.wav through heather_hour11.wav) with the full
//      Westminster chime sequence and gongs for each hour.  You would also
//      need heather_song15.wav, heather_song30.wav, and heather_song45.wav
//      files with the appropriate Westminster chime sequences.
//
//
//   The cuckoo chime clock:
//     The cuckoo chime clock signals the time by playing .WAV files at the
//     hours and at intervals throughout the hour.  It is activated via:
//        TH #H   - from the keyboard
//        /th=#h  - from the command line
//
//     The "heather_chime.wav" file is played x times on the hour (where x is
//     the current hour).  In addition the file is played once (#-1) times 
//     during hour.  For instance /th=4h says to play the file x times at the 
//     hour and  3 more times times during the hour (every 15 minutes).  The 
//     file "heather_chime.wav" should be less than once second long.
//
//     If # is 0 or not given, the chime clock is disabled.
//
//     If the cuckoo chime clock is activated a single musical note symbol is
//     shown near the upper left hand corner of the screen.
//
//
//   The ships bell clock:
//     The ships bell clock signals the time in ships bells format. Ships bells
//     sound on the hour and half hour.  Ships bells mode is activated by:
//       TH 1B   - from the keyboard enables ships bell mode
//        /th=1b - from the command line enables ships bell mode
//     The bell sound is from the file "heather_bell.wav"  This file should be
//     less than two seconds long.
//
//     if 0B is used instead of 1B, the ships bell clock is disabled.
//
//     If the ships bell clock is activated a '#' symbol is shown near
//     the upper left hand corner of the screen.
//
//
//   The tick clock:
//     Entering  "1T" for the clock type enables the ticking clock.
//     This mode sounds a tick on the second.
//
//     Entering  "2T" for the clock type enables the minute clock.
//     This mode sounds a beep on the minute.
//
//     Entering  "3T" for the clock type enables the minute beep / ticking
//     second clock.  This mode sounds a beep on the minute and a tick 
//     sound on the second.
//
//     Normally the tick clock sounds when the receiver time message comes
//     in.  By adding a "F" to the command, the "fine tick clock" will be
//     enabled.  This mode attempts to align the ticks to real time by
//     adjusting the ticks for the /tsx (or TO) message delay offset.
//     Note that the fine tick clock may not work well with some "polled" 
//     receivers... the Brandywine GPSDO is particularly bad in tick clock
//     mode   ... 
//      
//     If the file "heather_minute.wav" exists in the heather installation
//     directory exists, this file is played on the minute instead of the
//     beep sound.
//      
//     If the file "heather_second.wav" exists in the heather installation
//     directory exists, this file is played on the second instead of the
//     heather_click.wav sound file. If neither file exists then a BEEP
//     is used.
//
//     Entering "0T" for the singing clock type disables the tick/beep clock.
//
//
//
//    Note that the Windows versions of Heather plays sound files via the
//    PlaySound() system call,  the Linux versions use system() to spawn a 
//    /bin/sh command to the "aplay" program,  and macOS spawns a /bin/sh 
//    command to the "afplay" program.  If your system does not support these 
//    sound file player programs,  modify the function "play_tune()" 
//    in file heather.cpp
//
//  
//  EGG TIMER ALARMS
//
//  Heather supports two types of alarms:
//    An "egg timer" mode where a countdown timer is started and when it
//    reaches 0, the file "heather_alarm.wav" is played. The alarm sound is
//    usually played continuously (and the screen flashes) until a key
//    is pressed which cancels the alarm.  You can set the timer to only
//    play the sound file once by following the time interval with the
//    letter "o".  You can set the timer to automatically repeat by following
//    the time interval with the letter "r"
//
//
//    To start the timer from the keyboard:
//      TA 5S    - sound the alarm continuously after 5 seconds
//      TA 10M   - sound the alarm continuously after 10 minutes
//      TA 3H    - sound the alarm continuously after 3 hours
//      TA 2D    - sound the alarm continuously after 2 days
//      TA 10MO  - sound the alarm once after 10 minutes
//      TA 20MR  - sound the alarm continously every 20 minutes
//      TA 30MOR - sound the alarm once every 30 minutes
//
//    You also set the timer from the command line with the "/na=" command
//    line option:
//      /na=5s  - (see the keyboard commands listed above for the various
//                 timer modes)
//
//    If a countdown timer is enabled and the watch display is enabled, a
//    YELLOW tick mark is shown at the edge of the watch face.
//
//
//
//  ALARM CLOCK MODE:
//    Heather has an alarm clock mode where you specify a time (and optional 
//    date) for the alarm to sound. The commands are the same as for the egg
//    timer, but you specify a specific time (and optional date) for the 
//    alarm instead of an interval.  Alarm clocks are always a repeating
//    alarm and must be manually canceled unless a date has been specifed.
//    If a date has been specified the alarm setting is cleared once the
//    alarm has sounded and the user stops the alarm (by pressing a key).
//
//    TA 14:15:16   - sound the alarm continuously every day at 14:15:16
//    TA 14:15:16o  - sound the alarm once every day at 14:15:16
//    TA 8:0:12 2016/12/25  - sound the alarm at 8:00:12 on 25 December 2016
//    TA 8:0:12 12/25/2016  - sound the alarm at 8:00:12 on 25 December 2016
//
//    If you set an alarm time that is before the current time, the alarm
//    sounds on the next day.
//
//    You also set the alarm from the command line with the "/na=" command
//    line option:
//      /na=14:15:16  
//      /na=14:15:16,2016/12/15 (note non-space char between time and date
//      /na=14:15:16o2016/12/15  is needed on command line alarms)
//
//    Dates can be of the form yyyy/mm/dd, dd/mm/yy, or dd/mm/yyyyy.
//    If only a date is given, the time is assumed to be 00:00:00 on that date.
//
//    If an alarm clock is enabled and the watch display is shown, a
//    RED tick mark is shown at the edge of the watch face.
//
//    Note that if you have one of the astronomical time zones set (such 
//    as GMST) alarms are normally based upon your LOCAL time zone time and  
//    NOT the displayed astronomical time.  You can force the alarms to be
//    triggered based upon the displayed astronomical time with the "OT" 
//    keyboard command. This is the reason you should include your time zone 
//    hour offset when using an astronomical time scale. e.g.  /tz=GMST6GMST
//
//
//    Following the setting string with an "A" enables "modem alarms". This
//    uses the modem control signals DTR and RTS to signal when an alarm
//    is sounding.  The modem control signals default to DTR=+12V RTS=-12V.
//    When the alarm is sounding DTR will be -12V and RTS will be +12V. 
//    (OK, the actual voltage is dependent upon your serial port driver).
//    For instance: 
//       T4SA 
//    will use the modem control signals to inform an external device that
//    an alarm or egg time has triggered.
//    YOU SHOULD NOT USE MODEM ALARMS WITH an ACRON ZEIT receiver or if
//    active temperature control is in use... these use the modem control
//    signals for other stuff.
//       
//
//
//  SCHEDULED KEYBOARD SCRIPT RUN:
//    Heather has a mode where the keyboard script file "timer.scr" can be
//    automatically run after a specified time interval or at a specified 
//    time and/or date.  You specify a time (and optional date) for the
//    timer script to be run. The keyboard script commands are very
//    similar to the egg timer and and alarm clock commands.
//
//    TP 14:15:16            - run the script every day at 14:15:16
//    TP 8:0:12 2016/12/25   - run the script at 8:00:12 on 25 December 2016
//    TP 8:00:12 12/25/2016  - run the script 8:00:12 on 25 December 2016
//    TP 1h                  - run the script in one hour.
//    TP 100mr               - run the script every 100 minutes.
//
//    You also set script time from the command line with the "/np=" command
//    line option:
//      /np=14:15:16  
//      /np=14:15:16,2016/12/15 (note non-space char between time and date
//      /np=14:15:16o2016/12/15  is needed on command line alarms)
//
//    Dates can be of the form yyyy/mm/dd, dd/mm/yy, or dd/mm/yyyyy.
//    If only a date is given, the time is assumed to be 00:00:00 on that date.
//
//    Note that if you are typing on the keyboard while the timer script
//    is being run, the script will be interrupted.
//
//
//
//
//  KEYBOARD SCRIPT FILE ALARM WAITS
//    If, in a keyboard or timer script file, you follow an egg timer or alarm
//    clock time with the letter "W",  the processing of the script file will
//    be paused until the alarm triggers.  The command that sets the alarm
//    time MUST be the last command on the line AND the next line in the
//    script file MUST be a blank line or comment!
//
//
//
//  SCHEDULED EXTERNAL PROGRAM EXECUTION:
//    Heather has a mode where an external program can be automatically
//    run after a specified time interval or at a specified  time or date.
//    You specify a time (and optional date) for the program to be run.
//    The scheduled program execution commands are similar to the
//    egg timer and and alarm clock commands.
//
//    TC 14:15:16            - run the program every day at 14:15:16
//    TC 8:0:12 2016/12/25   - run the program at 8:00:12 on 25 December 2016
//    TC 8:00:12 12/25/2016  - run the program 8:00:12 on 25 December 2016
//    TC 1h                  - run the program in one hour.
//    TC 100mr               - run the program every 100 minutes.
//
//    You also set the program execution time from the command line with 
//    the "/nc=" command
//    line option:
//      /nc=14:15:16  
//      /nc=14:15:16,2016/12/15 (note non-space char between time and date
//      /nc=14:15:16o2016/12/15  is needed on command line alarms)
//
//    Dates can be of the form yyyy/mm/dd, dd/mm/yy, or dd/mm/yyyyy.
//    If only a date is given, the time is assumed to be 00:00:00 on that date.
//
//    The name of the program to run is fetched from the "HEATHER_EXEC"
//    environment variable.  If HEATHER_EXEC has not been defined, the
//    program "heather_exec" is run.
//
//    The /ne command line option disables the file editing and execution
//    commands.  Once /ne is used, it cannot be re-enabled.  This command is
//    a security measure to block possible malicious exploitation of these
//    features.  On Linux/macOS "/ne /ne" also disables playing of sound files
//    vis system() calls to APLAY.
//    
//    
//
//  AUTOMATIC PROGRAM EXIT
//
//    You can configure Heather to automatically quit at a given time or after
//    a given time interval.  This works just like the egg timer mode or alarm
//    clock mode.  The commands to do this are:
//       TX   - from the keyboard - see TA command for details 
//       /nx  - from the command line  - see /na command for details  
//
//
//
//  AUTOMATIC LOG FILE DUMPS
//
//    You can configure Heather to automatically write the plot queue data
//    to a log file at a given time or after given time interval.  This works 
//    just like the egg timer mode or alarm clock mode.  The commands to do 
//    this are:
//       TL   - from the keyboard  - see TA command for details  
//       /nl  - from the command line  - see /na command for details  
//
//    The format for the scheduled log dump files defaults to ASCII (or XML
//    for the HP-5071A).  You can change this with command line options:
//       /fg  - toggle .GPX format for scheduled log file dumps
//       /fx  - toggle .XML format for scheduled log file dumps
//
//    If the command setting contains the 'o' character
//    the file "tblog.log" is re-written each time a dump
//    occurs.  Without the 'o' character,  the file 
//    "tbyyyy-mm-dd-#.log" is written (where #) is an incrementing
//    sequence number.  See the /fg and /fx commands for using .gpx and .xml
//    log formats.
//
//    Example:  to write the log dump to the file "tblog.log" every 30 minutes 
//    use the command line option "/nl=30mor" or "TL 30mor" from the keyboard.
//    (the 30m says do it every 30 minutes, the "o" says to do it to
//     one file,  the "r" says to do it on a repeating basis).
//
//    You can change the "tb" prefix using in automatic log dump file names
//    with the /wp=prefix command line option.   
//
//
//
//  AUTOMATIC SCREEN IMAGE FILE DUMPS
//
//    You can configure Heather to automatically write a screen dump image
//    to a .GIF file at a given time or after given time interval.  This works 
//    just like the egg timer mode or alarm clock mode.  The commands to do 
//    this are:
//       TD   - from the keyboard  - see TA command for details  
//       /nd  - from the command line - see /na command for details  
//
//    If the command setting contains the 'o' character
//    the file "tbdump.gif" is re-written each time a dump
//    occurs.  Without the 'o' character,  the file 
//    "tbyyyy-mm-dd-#.gif" is written (where #) is an incrementing
//    sequence number.  
//
//    Example:  to write the screen image to the
//    file "tbdump.gif" every 30 minutes use the command
//    line option "/nd=30mor" or "TD 30mor" from the keyboard.
//    (the 30m says do it every 30 minutes, the "o" says to do it to
//     one file,  the "r" says to do it on a repeating basis).
//
//    You can change the "tb" prefix using in automatic screen dump file 
//    names with the /wp=prefix command line option.   
//
//    Screen dump mode is indicated on the screen by a '!'
//    or !! next to the time mode indicator on the first
//    line of the screen.
//
//
//  If a leap-second is observed (seconds value = 60, duplicated xx:00:00 
//  time stamp, or duplicated xx:59:59 time stamp) then Heather automatically
//  does a screen dump to the file "leap_sec.gif"  On some receivers
//  this might capture the previous second (xx:xx:59)... such is
//  life.  When a leap-second screen dump is done, the leap second value
//  in the status column shows "Leap: captured" in YELLOW.  You can clear
//  this indication with the GR keyboard command.
//
//
//  Note that when a screen or log dump happens, Heather first creates the
//  the file "tblock", next the image/log file is written, and then the
//  "tblock" file is deleted.  This can be used by external scripts to 
//  minimize (but not totally eliminate) the chances of an external 
//  script/program accessing the dump file while it is being written.
//
//
//
//
//
//-SETTING THE SYSTEM TIME FROM GPS
//
//   By far the best way to keep your system time accurate is to use an
//   Internet time protocol like NTP.  This can keep the system clock highly
//   accurate and monotonic (i.e. it does not jump back and forth, it smoothly
//   increments at a rate to keep the system time accurate.
//
//   However, if you do not have an internet connection available, Heather can
//   set the system time from data available from the GPS receiver.  Heather
//   can set the system clock on demand,  every minute, every hour, every day,
//   or whenever the system clock diverges from the GPS time by more than "x"
//   milliseconds.
//
//      TS   - from the keyboard - set the system clock once to the current
//             receiver time.
//      /tso - from the command line - set the system clock once when Heather
//             starts up and has valid time from the GPS receiver.
//      /tsm - from the command line - set the system clock once a minute
//             (the time is set at hh:mm:06 local time)
//      /tsh - from the command line - set the system clock once an hour
//             (the time is set at xx:00:06 local time)
//      /tsd - from the command line - set the system clock once a day
//             (the time is set at 04:05:06 local time)
//      /tsa - from the command line - set the system clock anytime the system
//             clock differs from the GPS time by over 40 milliseconds (Windows)
//             or 10 milliseconds (Linux, macOS)
//      /tsa=msecs - from the command line - set the system clock anytime the 
//             system clock differs from the GPS time by over "msecs" 
//             milliseconds
//
//   Most operating systems require programs that manipulate the system clock
//   to have administrator / root permissions. You can check if Heather can
//   can set the system clock by issuing a "TS" command from the keyboard.
//   Within a few seconds you should hear a BEEP if the time set command was 
//   accepted.
//
//   Heather sets the system clock by "jamming" the time into the system. It
//   makes no attempt to keep the clock monotonically increasing.  This can
//   be a bad thing for some systems, but, well, beggars can't be choosers.
//
//   
//   GPS receivers typically send out a message once per second that contains
//   the time.  Heather uses when the last character of this message arrives 
//   to set the system clock.  One problem is that different receivers send the
//   the time message at different offsets from the true time.  Also variations
//   in the computer, operating system, receiver configuration, serial port, 
//   etc used can affect when the message actually arrives.
//
//   You can set the message offset time (in milliseconds) with the command
//   line option:
//      /tsx=milliseconds  or the TO keyboard command
//
//   Milliseconds can be positive (message arrives AFTER the true time value
//   encoded in the receiver time message) or negative (message arrives BEFORE 
//   the true time)  Most receivers have a 1PPS (pulse per second) output
//   signal that indicates true time.   Heather does NOT use the 1PPS signal.
//
//   If you do not set a message offset value, Heather uses a default value
//   for a typical model of that receiver.  For maximum accuracy you
//   you should set the message timing offset adjustment factor for your
//   particular system and receiver configuration.  Heather can help determine 
//   the message offset adjustment to use.
//
//   For this to work, your system time must be set accurately.  If you are
//   using a network time protocol like NTP, you should be good to go.
//   Otherwise let Heather set the system time with a "TS" command from the
//   keyboard.  
//
//   Then issue the "TK" keyboard command.  This starts measuring the
//   difference between the system clock and the receiver timing message times.
//   It builds a histogram table and also calculates an average value of the
//   message offset time.  For the histogram to work, the system and GPS time 
//   need to be within two seconds of each other.
//
//   When measuring the message timing the timing jitter is plotted in the G0 
//   plot and the message offset time is shown in the G9 plot.  Also ADEV
//   (Allan variance) tables are shown for the message offset time and jitter.
//   The G0 and G9 plots do not show up as options in the "G" keyboard menu,
//   but are available...
//
//   Let the system run for a minute or so.  Then issue the "TK" command 
//   again.  This should print a message at the bottom of the plot area like:
//
//      # msg offset time: /tsx=246.00 msec   max hits:10 points:34   avg:254.35 sdev:10.16
//
//   There are two values of interest in this message:
//      /tsx=246.00   and   avg:254.35 
//
//   These values should be close to each other.  The "/tsx" value is the
//   most common value in the histogram and the "avg:" value is the average
//   value seen.  Some receivers do not send the timing message in a consistent
//   manner.  If the "/tsx" value and the "avg:" value are not close or the
//   "SDEV:" (standard deviation) value is large then using the receiver for
//   setting the time may not give optimum performance.  The "TK" measurement 
//   mode also writes a ".jit" file with the histogram values and measurement
//   results.
//
//   With some receivers, Lady Heather's periodic polling
//   of the receiver for status info, etc can put spikes in
//   the timing measurements. If this is a problem use the
//   "/ix" command line option to disable the sending of commands
//   to the receiver.  The spikes should not affect the
//   message offset time measurements but can affect the
//   message jitter standard deviation measurements. Issue
//   the "/ix" command again to re-enable status polling.
//
//
//   Tell Heather what your system message offset is with the command line
//   option:
//      /tsx=msecs  - msecs is the value shown the the measurement results
//                    described above.  Or use TO from the keyboard.
//
//   Note that the "TK" timing measurement mode flogs the system CPU rather
//   hard.  You can see CPU usage stats approaching 100% in this mode. This
//   can produce heating that can affect the system clock rate after a while.
//   Ideally you should do the timing measurement test when the system has
//   been running normally (for you) for a while to let it settle down at your
//   typical operating temperature. The difference is probably not much, but
//   in the world of precision timing, every little bit helps.
//
//
//
//
//
//-SETTING THE GPS RECEIVER POSITION and DOING ANTENNA LOCATION SURVEYS
//
//   First a word about ALL the various values that Lady Heather reports...
//   The various values shown by Lady Heather are reported to a decimal
//   point precision represented by the data fields that the receiver
//   messages contain.  Just because your receiver says the altitude is
//   123.4567890 meters does NOT mean the altitude is actually ACCURATE to 
//   that many decimal places... Heather just shows what the receiver is
//   sending out...  garbage in, garbage out.
//   
//
//   Lady Heather shows the latitude/longitude/altitude position that the 
//   receiver is currently reporting.  It can show the position in various
//   formats.  From the keyboard:
//
//      GLD  - decimal format
//      GLS  - degrees/minutes/seconds format
//      GLR  - decimal radians
//      GLG  - decimal grads (400 grads in a circle)
//      GLI  - decimal mils  (6400 mils in a circle)
//      GLE  - ECEF (Earth Centered Earth Fixed) coordinates
//      GLH  - Maidenhead grid square (ham radio)
//      GLU  - UTM (Universal Transverse Mercator)
//      GLN  - NATO MGRS (Military Grid Reference System)
//
//      GLT  - toggle display of solid earth tide displacements and vertical
//             gravity offset (in uGals) instead of the normal lat/lon/alt
//             coordinates.  In GLT mode the lat/lon scattergram (GI keyboard
//             command shows the latitude/longitude earth tide displacement
//             in mm.
//
//      GLF  - show altitude in feet
//      GLM  - show altitude in meters
//      GLL  - show altitude in linguini (7.1429 standard linguini per meter)
//
//      GLP  - private location - latitude and longitude are not displayed.
//             (so you can publish screen shots without revealing the location
//              of your evil mad scientist volcano lair to the world)
//
//      GLA  - toggles autoscaling of the lat/lon/alt scattergram scale factor
//             to match the span of the lat/lon data values seen.  When 
//             autoscaling is enabled the "m/div" or "ft/div" value in the
//             scattergram header is shown in UPPERCASE.  Autoscaling the
//             scattergram can be useful if you are using the receiver in a
//             moving environment.
//
//             If you are in scattergram auto-scale mode and move the mouse
//             pointer into the scattergram area, the lat/lon location of the
//             mouse pointer will be shown below the scattergram.
//
//             WARNING: LLA autoscaling is currently experimental can can be
//             a bit flakey.  Before enabling autoscale mode make sure all
//             the lat/lon data in the plot queue is valid (i.e. no bogus or
//             0.0,0.0 lat/lon values due to receiver startup).  It's best
//             to clear the plot queue after the receiver starts producing
//             valid lat/lon values and before enabling autoscale mode.
//
//      /gld, etc - set the location format from the command line.  The
//                  command line option to use is the same as the keyboard
//                  commands listed above with a leading "/" or "-".
//
//      /t"  - toggle between degrees.minutes.seconds / decimal location format
//             (this is a legacy command for compatibility with earlier
//              version of Lady Heather).
//
//
//   Heather also records the lat / lon / alt data in the plot queue and
//   can display the location data in the plot area or as an X-Y "scattergram"
//   of distance from a reference point.  
//
//     G1  - from the keyboard - toggle the latitude plot on and off
//     G2  - from the keyboard - toggle the longitude plot on and off
//     G3  - from the keyboard - toggle the altitude plot on and off
//     GV  - from the keyboard - toggle the lat/lon/alt (G1 / G2 /G3) plots 
//           on and off
//
//     For the Zyfer Nanosync receiver the G1/G2/G3 plots show some 
//     undocumented information. These are HETE/HEFE/HEST.  These are thought
//     to be holdover estimated time error, holdover estimated frequency
//     error, and holdover estimated 24 hour error... but who knows
//
//     The G1/G2/G3 plots are also used to display other values for the
//     HP-5071A and TAPR TICC devices since these devices don't have
//     lat/lon/alt related values.
//
//
//   THE LOCATION FIX SCATTERGRAM
//
//     Heather can plot a "scattergram" of the location fix data relative to
//     a fixed reference point.  The reference point is the location  that
//     was active when the scattergram was activated.  The scattergram is
//     automatically enabled if a position survey is started.  Every hour the
//     color of the dots in the scattergram changes (14 colors are used).
//
//     You can change the scattergram reference point with the SR keyboard
//     command.  The SR command defaults to using the current lat/lon/alt.
//     If the lla scattergram reference has been manually set the lat/lon/alt
//     labels are shown in all upper case. They are normally in upper and
//     lower case.  Toggling the scattergram off and on cancels the user
//     set reference position.
//
//     If you use the letter 'A' for a location value then the current
//     average of the lat/lon/alt value will be used.  The average is
//     calculated from the data displayed in the plot area.  To use the
//     average of all data in the plot queue, first use the VA command to
//     display all plot data and "FD -1" to do a per-pixel average.
//
//     If you use '*' as a location value then the current value of the 
//     lat/lon/alt value will be used.
//
//     If you specify a sign of '++' or '--' before a lat/lon/alt
//     value the current location of that value will be moved by that
//     number of meters (or feet if in /t' mode).
//
//     The scattergram grid defaults to a resolution 3 meters or 10 feet 
//     per division (with +/- 5 divisions from the center reference point. 
//     You can change the scattergram grid scale factor with a command 
//     line option:
//        /tm=meters_per_division
//        /t'=feet_per_division
//        /tlg=linguini_per_division
//
//     You can also set the scattergram to auto-scale:
//     GLA  - toggles autoscaling of the lat/lon/alt scattergram scale factor
//            to match the span of the lat/lon data values seen.  When 
//            autoscaling is enabled the "m/div" or "ft/div" value in the
//            scattergram header is shown in UPPERCASE.  Autoscaling of the
//            scattergram can be useful if you are using the receiver in a
//            moving environment.
//     /gla - does GLA from the command line
//
//     GI   - toggle the lat/lon "scattergram" on and off from the keyboard.
//     /gi  - toggle the lat/lon "scattergram" on and off from the command 
//            line.
//     ZL   - zoom the scattergram to full screen
//     SR   - change the scattergram reference position
//
//            In earth tide display mode (GLT keyboard command) the lat/lon 
//            scattergram shows the latitude/longitude earth tide displacement
//            in mm. The scale is fixed at 12.5 mm per division.  This display
//            is not available with the HP5071 cesium beam oscillator.
//
//   Clicking the left mouse button on the lat/lon/alt information display
//   of the scattergram will zoom the lat/lon scattergram to full screen.
//   Clicking again will restore the normal screen display,
//   Note that short clicks might be ignored... particularly on devices
//   like UCCM receivers that only output time updates every two seconds.
//   It can help to hold down the mouse button until the screen changes.
//
//
//
//   ANTENNA LOCATION SURVEYS
//
//     Most GPS timing receivers and disciplined oscillators require a fixed
//     location for the antenna and its position must be known to very high
//     accuracy for optimum operations.  These devices can usually operate
//     in a "position hold" mode or a "3D fix / navigation" mode.  Position
//     hold mode is also called "overdetermined clock" mode.
//
//     The accurate fixed location can be input manually by the user or the 
//     receiver can automatically determine it by doing a "self-survey" where
//     it collects data for a period of time and averages/filters the readings
//     to come up with an accurate location.  Most receiver self-surveys last
//     for at least 20 minutes and may take hours.  Some devices let you
//     specify the time interval to survey for.
//
//     Lady Heather can also do a precision median survey to determine the
//     location.  This collects data for several hours (48 hours is the default)
//     and statisically processed the data using medians and averages over 
//     several time intervals to come up with a precise location that is usually
//     better than the standard receiver position survey.  The GPS satellite
//     orbits repeat on a roughly 12 hour basis (with 6 hours of visibility
//     for each orbit).  A 48 hour survey allows for 4 repeats of the complete
//     satellite constellation and allows the precision survey to mitigate
//     a lot of signal problems such as multi-path distortion.  If you cannot
//     wait for 48 hours,  24 hours works well, and 12 hours is OK.
//
//     If a precision survey is done, Heather logs the readings and results in 
//     a ".lla" file. Precision surveys can be done on receivers that do not
//     support a "position hold" mode.  After the survey completes you can
//     check the ".lla" file for the results.  The calculated position will be
//     shown at the end of the file.  Previous versions of Heather always 
//     wrote the file "lla.lla".  Heather now uses ????.lla where ???? is
//     based upon the receiver type.  To avoid lla log file name conflicts
//     you should not run more than one precision survey at a time if the
//     receiver types are the same.
//
//     Trimble Thunderbolt receivers do not have a command for entering the
//     position using double precision numbers.  Heather tries to write the
//     calculated precision location or the manually set location to the
//     device by doing single point self-surveys until one is within a foot
//     of the desired location.  This process takes an indeterminate amount
//     of time!
//
//     Interrupting a standard survey or precise position survey save 
//     will save the current location using the lower precision 
//     TSIP command.  So will exiting the program while a survey is
//     in progress.
//
//     Some GPSDO devices (mainly telecom surplus devices) do not have a
//     "navigation" mode that lets them output 3D fixes. You cannot do a 
//     precision survey on these devices.
//
//
//     To enter a location manually and set position hold mode:
//        SL   - from the keyboard.  The latitude and longitude can be in 
//               decimal or degrees/minutes/seconds format like 30d40m50.60s
//               Wherever Heather expects a lat/lon/alt string you can specify
//               a value of "loc" and the location will be read from the file
//               "heather.loc" (if it exists).
//
//     The SL command can also be used with devices that do not output
//     lat/lon/alt info. Entering a location for these devices allows the
//     astronomical / sun / moon features of Heather to work.  
//
//
//     The command that Trimble receivers use to set a position only uses
//     single precision floating point numbers.  These are not accurate enough
//     to resolve lat/lon to meter level precision.  The ST command can be
//     used to save a more accurate position by doing multiple single point
//     self surveys until one happens to land within 1 meter of the desired 
//     location.  This process can take an indeterminate amount of time
//     (incuding forever!).  Note that the ST command does not appear in 
//     the "S" keyboard menu.  To figure out which method of saving a position
//     on a Trimble receiver works best for your situation try:
//        1) set the precise location with the SL command
//        2) calculate the distance between the saved location and the entered
//           location with the SD commad (SD precice_lat precise_lon 0.0)
//        3) write down the calculated distance
//        4) do a precice location save of the precice location:
//           ST precise_lat precise_lon precise_alt
//        5) wait for the precice location save to end
//        6) calculate the distance between the new saved location and the
//           entered location with the SD command:
//               SD precice_lat precise_lon 0.0
//        7) if the new reported distance is greater than the old distance
//           from step 3, do step 1.
//
//     Heather can also get the location automatically from the file 
//     "heather.loc" in the Heather installation directory.  This file is 
//     only read if the main input device does not report a location (i.e. 
//     is not a GPS based device) or if you specify a value of "loc" when
//     Heather requests a lat/lon/alt location value.
//
//
//     If you use the letter 'A' for a location value then the current
//     average of the lat/lon/alt value will be used.  The average is
//     calculated from the data displayed in the plot area.  To use the
//     average of all data in the plot queue, first use the VA command to
//     display all plot data and "FD -1" to do a per-pixel average.
//
//     If you use '*' as a location value then the current
//     value of the lat/lon/alt value will be used.
//
//     If you specify a sign of '++' or '--' before a lat/lon/alt
//     value the current location of that value will be moved by
//     that number of meters (or feet if in /t' mode).  Note that moving
//     the lat/lon scattergram reference point is not available if
//     scattergram auto-scaling is enabled (GLA command).
//
//
//     To start a native receiver self survey:
//        SS   - from the keyboard.  It will request a value for the length
//               of the survey.  Depending upon the receiver type the length 
//               will be in samples, seconds, minutes, or hours.  A few
//               receivers can only perform a fixed length survey.  If a survey
//               is in progress, issuing SS again tries to stop the survey.
//        /ss[=length] - from the command line.  If a length is not specified
//               the survey length is device dependent (maybe 20 minutes or 1-3
//               hours).  If a survey is in progress and Heather is started with
//               /ss=0, Heather attempts to stop the survey.
//
//     To start a precision survey:
//        /sp[=hours]  - from the command line - do a precision survey,
//        SP   - from the keyboard.  It will request the length of the survey
//               in hours (up to 96 hours long)... the longer the better.  If a
//               survey is in progress, issuing SP again will stop the survey.
//
//
//
//     To force position hold mode:
//        SH   - from the keyboard - Some receivers remember their set position
//               hold locations and use that when position hold mode is
//               selected Other receivers will use the current position as
//               the hold position.
//
//     To force 3D navigation mode mode:
//        SN   - from the keyboard
//
//     Trimble Thunderbolt and related devices support several other positioning 
//     modes.  See the device manual for more information (0xBB packet).
//      
//        S0   - automatic 2D/3D navigation mode selection
//        S1   - single satellite mode
//        S2   - 2D mode (S2 actually sets receiver mode 3)
//        S3   - 3D mode (S3 actually sets receiver mode 4)
//        S4   - undocumented (3D?) mode (S4 actually sets receiver mode 2)
//        S5   - DGPS reference mode (disables timing functionality)
//        S6   - 2D clock hold mode
//        S7   - overdetermined clock mode (same as SH)
//
//
//
//   PROPOGATION TIME ESTIMATES (also distance to remote location)
//
//     Heather can calculate a (crude) estimate of the signal delay 
//     (propagation) time between your location and a distant transmitter 
//     using the SD command.  
//
//        SD lat lon ionosphere
//        SD lat lon
//        SD id ionosphere
//        SD id
//        SD km ionosphere
//        SD km
//
//     lat and lon are the transmitter location,  ionosphere is the
//     height of the ionosphere in km.  If ionosphere is not given, 
//     it is estimated based upon your hemisphere and the time of year.
//     Negative lat values are in the southern hemisphere, negative lon
//     values are the western hemisphere.
//
//     Or you can specify a distance in km by following the first number
//     with the letter 'k'.
//        SD 123k 100  (123 km to station, 100 km ionosphere height)
//        SD 300000k   (300,000 km to station , calculated ionosphere height)
//
//     You can also use the SD command to calculate the lat/lon great circle 
//     distance to a location (ignoring the altiude difference).  Normally
//     distance is shown in km/miles.  If the distance is less than 1 km, it
//     will be shown in meters/feet.  This can be useful if you want to 
//     calculate the distance between the GPS receiver reading (like the
//     position hold location) to a post-processed precise location.  To use
//     the SD command to calculate a great circle distance difference, specify
//     an ionosphere height of 0.0 meters.  Note that there can be a 1mm
//     residual offset in the calculated distance.
//
//
//     Instead of specifying the transmitter lat and lon, Heather has a list
//     of known station ID's you can use:
//        ANTHORN
//        BBC  (Droitwich)  
//        BPM    
//        CHU    
//        DCF    
//        EBC    
//        HBG    
//        HLA    
//        JJY    
//        KYUSHU 
//        LOL    
//        MIKES  
//        MSF    
//        PPE    
//        RBU    
//        RTZ    
//        RUGBY  
//        RWM    
//        TDF    
//        WWV    
//        WWVB   
//        WWVH   
//        YVTO   
//
//    To clear the propagation time results from the screen use the GR command.
//
//
//
//
//   INCLUDING and EXCLUDING SATELLITES
//
//     Several receivers let the user exclude certain satellites from being 
//     tracked,  force or restore the inclusion of satellites, or operating
//     the receiver in a single satellite mode.
//
//     SO   - from the keyboard controls single satellite mode.  Trimble
//            receivers can be configured to track a specific satellite or
//            automatically select the highest elevation satellite.  For
//            other receivers Heather offers to track the highest satellite
//            or the user can select a particular satellite... eventually
//            that satellite will fall below the horizon and the receiver 
//            won't be tracking anything...  Non-timing receivers are not able
//            to work in a single-satellite mode.
//
//     SX   - from the keyboard controls excluding/including of satellites.
//            (currently only one satellite may be excluded)
//
//
//
//   CONFIGURING THE SATELLITE CONSTELLATION TYPES TO USE
//
//     Many modern GPS receiver are actually GNSS receivers... they can work
//     with more than one satellite system: GPS/GLONASS/BEIDOU/GALILEO/SBAS/
//     QZSS/IMES, etc.  Heather lets you control which satellite systems to
//     track.  Note that most GNSS receivers have limits on which systems can
//     be enabled at the same time. Consult your receiver manual for 
//     information on what it can do.
//
//
//     SG   - from the keyboard controls the GNSS satellite system
//            congiguration.  You will be prompted to input a string of 
//            characters that indicate which systems to use.  The currently
//            enabled systems will be offered as the default entry.
//
//            The letters that are used to select a particular satellite
//            system were changed in v6.04 to match the international 
//            standard ones used in RINEX files.
//
//
//
//
//
//-THE SATELLITE INFORMATION DISPLAYS
//
//   Heather has three main satellite information displays:
//      1) The satellite information table
//      2) The satellite position map
//      3) The satellite signal maps
//
//   The satellite information table lists the currently visible and tracked
//   tracked satellites and various information about them:
//      Satellite PRN and GNSS id char (that identifies the sat and GNSS system)
//      Satellite azimuth angle
//      Satellite elevation angle
//      Satellite signal level
//
//   GNSS system id chars (next to the PRN columns) are:
//      G - GPS     (USA)
//      S - SBAS    (USA)
//      R - GLONASS (Russia)
//      E - Galileo (Europe)
//      C - BEIDOU  (China)
//      J - QZSS    (Japan)
//      I - IRNSS   (India)
//      M - IMES    (IMES is not a RINEX supported system)
//
//   Depending upon the receiver type, the information table can also show
//   extra things like:  doppler shift, tracking state, carrier phase, code
//   phase, clock bias, URA (range accuracy).
//
//   A normal GPS receiver may be able to track around 14 satellites at once.
//   More modern receivers that can also track GLONASS, GALILEO, BEIDOU, SBAS
//   and other satellites might be tracking over 32 satellites at once.
//   Normally Heather expects to show up to around 14 satellites, and
//   displaying 32 satellites at once can cause problems fitting all that data
//   on the screen.  You can control the size and format of the satellite
//   information table display:
//
//       SI    - from the keyboard
//       /si=# - from the command line.
//
//   Clicking the left mouse button on the satellite information display
//   will zoom the sat info information table to full screen.
//   Clicking again will restore the normal screen display,
//   Note that short clicks might be ignored... particularly on devices
//   like UCCM receivers that only output time updates every two seconds.
//   It can help to hold down the mouse button until the screen changes.
//
//
//   If you don't use the SI commands to specify the maximum number of 
//   satellites to show information for, Heather will show up to 14 satellites.
//   The satellite information display size automatically adjusts as more
//   satellites are seen.  If you set a value, Heather forces the display size
//   to that value.  
//
//   If you input a number without a +/- sign, Heather displays all the 
//   information it has for up to the specified number of satellites.  Note
//   that the +/- sign can be used either before or after the number.
//
//   If you input a negative number,  Heather shows the short form of the
//   info for up to that number of satellites.  The short form display frees
//   up enough space to the right of the satellite info display to show
//   the sun / moon information display.  If the receiver type in use does
//   not report any extended information,  the sun/moon info display is 
//   automatically enabled.
//
//   The sun / moon info is shown in yellow if there is a possible eclipse
//   condition (currently only works for solar eclipses).
//
//   If you input a number with a "+" sign, Heather shows the short form
//   information in two columns (but does this not leave room for the 
//   sun/moon information).  This helps with displaying information for 
//   receivers that can track multiple satellite systems.
//
//   If you follow the number with a "t", only satellites that are being
//   actively TRACKED are shown in the satellite information table and
//   satellite map display.  The GCT keyboard command also lets you toggle
//   the display of un-tracked satellites.
//
//
//   The more rows of satellite information being displayed, the less space
//   there is for the plot area.  Combine lots of rows of satellite info
//   with the digital clock display on a small screen and you can wind up with
//   an unusable plot display or unreadable keyboard menus.  Turning off the
//   digital clock display (GZ) can help with the screen formatting.
//
//   If more satellites are visible that you have allocated space for, the
//   info for the excess satellites is not shown and a message is shown
//   saying to click on the satellite information table.  If you click on the
//   satellite table the screen is zoomed to show all satellite information.
//
//   Satellites that are being actively tracked are shown in GREEN
//   Satellites that are visible, but not being tracked are YELLOW
//   Excluded/disabled/blocked satellites are shown in BLUE
//   Unhealthy satellites are shown in RED (if the receiver reports satellite
//   health)
//
//
//   Heather graphs the number of actively tracked satellites in the plot
//   window and can flag whenever the sats being used for calculating
//   fixes changes:
//
//      GCG  - Enables the tracked satellite count plot menu (same as G$)
//             The sat count plot does not scale or auto-center. The satellite
//             count plot is always at the bottom of the plot area.
//             The satellite count plot is shown in CYAN at the bottom of
//             the plot window.  Each minor division equals one satellite.
//             For screen resolutions less than 800x600, each minor division
//             represents two satellites.
//
//      GCC  - toggles the display of changes in the actively USED
//             satellite constellation.  When the list of satellites being
//             actively tracked and USED FOR FIXES changes a small tick 
//             mark is shown shown at the bottom of the plot area.  The
//             actively used satellites are the ones shown in GREEN in
//             the satellite list.  See the section on the FD (filter display)
//             command for information about how setting the plot view
//             interval to show more than one reading per pixel can mask
//             seeing all the satellite changes.
//   
//   
//   You can sort the satellite information table using the following
//   keyboard commands.  You can sort in descending order by including
//   "-" character.  Ascending sort is the default for most plots.
//   If you sort by one of the values, the header of that column is shown
//   in GREEN.  If you don't specify a sort, the table is sorted by PRN
//   number in ascending order.  Note that if a value is 0, this usually
//   means that the value is unavailable or invalid.  These values always
//   appear at the end of the satellite list.  If you attempt to sort on
//   a value that the receiver does not output, the list winds up being
//   sorted by PRN.
//
//      GCA - sort by azimuth
//      GCB - sort by clock bias
//      GCD - sort by doppler
//      GCE - sort by elevation
//      GCP - sort by PRN (default)
//      GCR - sort by pseudorange
//      GCS - sort by signal level
//      GCW - sort by carrier/code phase
//
//      GCT - toggle display of non-tracked satellites
//
//
//   The SQ keyboard command allows plotting the az/el/signal level of a
//   specified satellite, the sun, or the moon.  SQ mode is not available
//   if an environmental sensor is being used... it uses the same plot queue
//   entries.  This also means that the earth tide plots are not available
//   in SQ mode.  The SQ command also resets all the data queues whenever it
//   is executed.  The GK keyboard command is used to access the sat prn
//   plots.  For the sun and moon, the signal level is repoted as -40 or 40
//   depending upon if it as below or above the horizon.  The satellite that
//   is being plotted is identified by an '*' next to its PRN value in the
//   satellite information table.
//
//
//   The SB command causes a particular satellite in the satellite map to 
//   blink once a second.
//      SB # - user specified PRN #
//      SB H - current highest satellite
//      SB P - the plot satellite specified by the SQ command
//
//
//   Besides the satellite information table, Heather has two other satellite
//   information displays... the satellite map and the signal level map:
//
//
//   THE SATELLITE POSITION MAP:
//
//   The satellite map shows a map of the currently visible / tracked 
//   satellites. It is enabled by:
//       GM   - from the keyboard
//       /gm  - from the command line
//       ZM   - zoom the satellite map to full-screen
//       ZB   - zoom the satellite map and watch to full-screen
//
//   Clicking on the map or watch displays on the screen will zoom it to full 
//   screen.  Clicking again will restore the screen to its previous state.
//   Note that short clicks might be ignored... particularly on devices
//   like UCCM receivers that only output time updates every two seconds.
//   It can help to hold down the mouse button until the screen changes.
//
//   The satellite map shows the satellites as circles on an azimuth/elevation
//   grid.  The size of the circles depends upon the current signal level.
//   Satellites that are currently being tracked are shown as filled in
//   colored circles.  Satellites that are visible are shown as hollow circles.
//
//   The /so=# command line option lets you change the shape of the satellites
//   in the map:
//      /so=0 - round sats
//      /so=1 - square sats
//      /so=2 - round sats with "bat-wings"
//      /so=3 - rectangular sats with "bat-wings"
//      /so=4 - rectangular sats with "linear wings"
//      /so=5 - rectangular sats with "linear wings"
//
//   If you hold the mouse cursor over a satellite circle on a map display
//   that satellites' PRN, azimuth, elevation, and signal level will be
//   shown below the map... if there is enough room on the screen for it (i.e.
//   the map has the "Satellite positions" label below it).
//
//   The position history of each satellite is shown as a "trail" behind the
//   satellite.  The trail has small time marker circles drawn on it.  Solid
//   circles indicate hours and hollow circles indicate half hours. The trail
//   shows the last 6 hours of the satellite position.  The drawing of satellite
//   position trails can be toggled with:
//      /st  - from the command line - toggle display of satellite trails
//      /sd  - from the command line - toggle display of time markers on the
//             satellite trails
//
//
//   The satellite position map includes a representation of the sun at its 
//   current location in the sky.  The sun is shown in solid YELLOW if it is 
//   visible and as a hollow YELLOW circle if it is below the horizon. The sun
//   symbol is shown surrounded by sun rays in order to distinguish it from
//   satellites.  The moon is also drawn showing its current phase.  It is
//   shown in YELLOW if above the horizon and GREY if below the horizon.
//
//
//
//   If both the satellite position map and the watch display are enabled they
//   will overlay each other on the screen if there are not two places 
//   available to draw them (the GB and /gb commands allow one of the displays 
//   to be drawn to the right of the plot area).
//
//   The GB command is labeled "Both map and adev tables" in the keyboard menu
//   but is more properly "allow map displays in the plot area."
//
//
//
//   Note that on SCPI, UCCM, STAR, and ACRON receivers the message that sends 
//   the satellite position and signal data takes a long time for the receiver
//   to send.  Heather only requests it once per minute at hh:mm:33.  These
//   satellite information messages block the sending of time code messages
//   and causes time code skip errors... Heather automatically ignores any
//   time code errors caused by these messages.  Heather has some code to
//   "fake" the missing time messages on most receivers.
//
//
//   Note that the RFTG-m XO unit does not report satellite positions. Heather
//   will fake the satellite positions at AZ=(prn*10) and EL=20 degrees.  This
//   hack lets you see what sats are being tracked and their signal levels,
//   but not their true positions... such is life.
//
//
//
//   THE SIGNAL LEVEL MAPS:
//
//   The signal level maps show a map of the satellite signal levels as a
//   function of satellite azimuth/elevation.  The values used are the AVERAGE
//   value of the signal level of all satellites seen a given position in
//   the sky.  The signal level map can be shown in several different formats.
//
//   signal level map   - shows a color coded display of the average signal
//                        level seen across the sky.  Data is interpolated
//                        to fill in spaces between observed positions.
//
//   data               - this is similar to the signal level map, but the map 
//                        is not interpolated between missing points.
//
//   azimuth            - shows a map of the relative signal level seen at
//                        each azimuth angle.
//       
//   elevation weighted - shows a map of the relative signal level seen at
//                        each azimuth angle weighted by 1.0/elevation.
//                        Weighting the signal levels by the inverse of the
//                        satellite elevation compensates for the normal
//                        behavior of satellite signals being better at 
//                        higher angles and better shows the effects of
//                        antenna obstructions.
//
//   elevation          - shows a map of the relative signal level seen at
//                        each elevation angle.  Note that a YELLOW tick mark
//                        appears at the edge of this map.  This is the 
//                        elevation angle where satellite signal levels begin 
//                        to rapidly drop off.  A BLUE tick mark indicates the
//                        satellite elevation mask setting.
//
//   From the keyboard:
//       GQ   - toggle signal level map on and off
//       SAS  - toggle signal level map on and off
//       SAW  - toggle signal level elevation weighted data map on and off
//       SAE  - toggle signal vs elevation map on and off
//       SAA  - toggle signal level vs azimuth map on and off
//       SAD  - toggle signal level data map on and off
//
//   From the command line
//       /gq  - toggle signal level map on and off
//       /gqs - toggle signal level map on and off
//       /gqq - toggle signal level map on and off
//       /gqw - toggle signal elevation weighted level map on and off
//       /gqa - toggle signal level vs azimuth map on and off
//       /gqe - toggle signal vs elevation map on and off
//       /gqd - toggle signal level data map on and off
//         
//    SAA - displays relative signal level seen at each
//          azimuth angle
//    SAW - displays relative signal level seen at each
//          azimuth angle,  with the signal strength
//          weighted inversely with elevation angle.  This
//          highlights low elevation antenna blockages and
//          low orbit angles that have no satellites.
//    SAE - displays relative signal level seen at each
//          elevation angle
//    SAS - displays color coded map of the absolute signal 
//          level seen at each azimuth/elevation point.
//    SAD - shows satellite signal level data points
//          (much like the GM satellite position map)
//    SAC - clears the old signal level data and starts 
//          collecting new data. You can also do this with
//          the CM keyboard command
//
//
//   You can zoom the various satellite maps to full screen from the "Z" 
//   keyboard menu.  Any keypress (except '\') will exit the zoom screen mode.
//   A '\' will dump the screen image to a .gif file.
//
//   You can also force a screen dump by left-clicking on the screen where
//   the "Receiver data" info is near the upper left hand corner of the
//   screen.  This is handy if you are using a touch-screen.
//
//   Note that it can take several hours for the map to fill in.  The more
//   satellites that your receiver can track, the faster the map fills in.
//
//   Note that the satellite position and signal level maps are affected
//   by the settings of the elevation mask and signal level mask filters.
//   If you want a complete view  of your antenna system performance then
//   first set those filters to their lowest settings.
//
//   The signal level maps show the current setting of the satellite elevation
//   mask filter with a dotted circle at the elevation mask angle.  You can
//   disable the display of the elevation mask angle circle:
//      GJ  - from the keyboard
//      /gj - from the command line
//
//
//   You can reset the satellite map and signal data with the keyboard command:
//       CM   - clear out the satellite map data 
//
//   You can write the current signal level information to a ".sig" file.
//   The signal level file contains some comments and a list of az/el/snr
//   values.
//       WZ   - writes the signal level data to a file.
//
//   You can read a ".sig" file from the "R" keyboard command. Note that
//   reading a ".sig" file pauses updating the plot queue with new values.
//   You can resume plot queue updates with the "U" keyboard command.
//
//
//
//
//-ZOOMED SCREEN DISPLAYS:
//
//      ZA - zoom the elevation weighted Azimuth map to full screen
//
//      ZB - zoom Both the watch and satellite map displays to full screen 
//           overlayed on each other.
//
//      ZC - zoom the Clock display to full screen.
//
//      ZD - zoom the signal level Data map to full screen.
//           If one of the signal quality maps is shown you can click the 
//           mouse to show all the signal quality maps (ZU command)
//
//           For the HP-5071A, LPFRS, RMO, Lucent RFTG-m, SRO100, PRS-10, and
//           X72 devices, ZD zooms the screen to a full device Data display.
//
//      ZE - zoom the signal level vs Elevation map to full screen
//
//      ZH - brings up a receiver data monitor screen. Received message data
//           is formatted into hex+ASCII lines.  Binary data packets are
//           labeled with their name (where possible).
//
//      ZI - zoom the satellite Information displays to full screen
//
//      ZL - zoom the position fix scattergram to full screen
//
//      ZM - zoom the satellite Map to full-screen
//
//      ZN - zoom the screen do a Null (blank) display
//
//      ZO - brings up a data mOnitor screen. Received message data bytes
//           are shown in GREEN and sent data is shown in YELLOW.
//
//      ZP - zoom the Plot window to full screen
//
//      ZQ - zoom the screen to a calendar display.  The calendar shows a few
//           previous month(s) and the next "x" months.  The current month is
//           shown in GREEN.  Months before the requested staring data are 
//           shown in GREY, and later months are shown in WHITE. "x" is 
//           determined by what will fit on the srceen.
//
//           Clicking on the lower left corner of the calendar screen or
//           pressing the '-' key moves the calendar back a month.
//           Pressing the '<' key moves the calendar back a year.
//
//           Clicking on the lower right corner of the calendar screen or
//           pressing the '+' key moves the calendar forward a month.
//           Pressing the '>' key moves the calendar forward a year.
//
//           You can preceed the +,-,<,> commands with a number from 0..10000.
//           (note that there will not be any indication of you typing the
//           adjustment number).  The adjustment number gets cleared when
//           you execute the adjustment. 
//
//           The current day will blink every second.
//           Days of daylight savings time switchover are shown in BLUE.
//           Days that have full/blue moons are shown  in YELLOW.
//           Days that have new/black moons are shown in BROWN.
//             The moon phase dates are calculated with a resolution
//             of 1-2 hours.  If the new/full moon appears around 
//             midnight local time, the date shown in the calendar may be off 
//             by a day.  The moon phase calendar information may not be 
//             accurate outside of the years 2000..2100
//           Days that have an entry in the greetings calendar are shown
//           in CYAN.  
//
//           The TB keyboard command lets you show a calendar for a specifed
//           year (and optional starting month).
//
//      ZR - zoom the Relative signal level map to full screen
//
//      ZS - zoom the Signal quality map to full screen
//
//      ZU - zoom all signal level maps to full screen
//
//      ZV - zoom the watch, sat map, signals full screen
//           If the ZU or ZV screen is showing you can click the mouse
//           on one of the displayed items to zoom it to full screen.
//
//      ZW - zoom the Watch display to full screen.
//
//      ZX - zoom the watch, satellite, and signal quality maps to full screen
//           overlayed on each other
//
//      ZY - zoom the satellite map and signal quality map to full screen
//           overlayed on each other
//
//      ZZ - rerurn the screen to the normal un-Zoomed state
//
//      ZT - sets a keyboard inactivity Timeout (in minutes).  After the 
//           specified time has passed without any keyboard activity, the 
//           screen switches to the specified zoomed screen display.  This
//           will not happen if the screen is aready showing a zoomed screen 
//           or a keyboard menu is being shown.  The default timeout display
//           is the digital clock.
//
//
//
//
//-SUN and MOON INFORMATION DISPLAY
//
//   Besides displaying information about the GPS satellites, Lady Heather 
//   calculates the position of and other relevant information about the sun 
//   and moon:
//
//     Sun azimuth and elevation in the sky
//     Moon azimuth and elevation and phase (illumination percentage)
//     Sun rise/transit/set times
//     Moon rise/transit/set times
//     Current solar equation of time.
//     Current moon "age" from the start of the lunar month (new moon).
//
//   The sun/moon information table is shown to the right of the satellite
//   information table.  Enabling the sun/moon information automatically
//   selects the short form of the satellite information display.
//
//   The sun rise and set times are based upon the sun's position above the
//   horizon. There are several definitions of sun rise/set:
//      Physical - when the top edge of the sun crosses the horizon
//      Official - when the sun crosses 0.833 degrees below the horizon
//                 (this angle is for atmospheric refraction effects)
//      Civil    - when the sun crosses 6 degrees below the horizon
//      Nautical - when the sun crosses 12 degrees below the horizon
//      Astronomical - when the sun crosses 18 degrees below the horizon
//      Islamic  - when the sun crosses 18 degrees below the horizon at sunrise
//                 or 17 degrees below the horizon at sunset
//      User defined - you can specify any angle above (positive) or 
//                     below (negative) the horizon.
//
//   Sun/moon times are shown as local time zone times for the current date.  
//
//
//   To display the sun (or moon) rise/set times use:
//      TR    - from the keyboard
//
//      TR P  - display "Physical" sunrise/sunset times
//      TR O  - display "Official" sunrise/sunset times
//      TR C  - display "Civil" sunrise/sunset times
//      TR N  - display "Nautical" sunrise/sunset times
//      TR A  - display "Astronomical" sunrise/sunset times
//      TR I  - display "Islamic" sunrise/sunset times
//      TR #  - (where # is the user defined solar horizon angle[s]
//              negative values are for angles below the horizon, positive
//              values are for angles above the horizon)
//              You can specify independent solar rise/set horizons like:
//                 TR -18,-17
//
//      TR M  - display moon rise/transit/set times instead of the sun times.
//
//      /sr=#  - from the command line where # is the sunrise type selection
//               character shown above.  For example
//                  /sr=c says to show civil sunrise/sunset times.
//
//   Heather can also play sound files at rise/set or transit (solar noon):
//      Include an "*" after the command:
//         TR O*
//         /sr=o*
//         /sr=o    - disables sunrise/transit/set sound
//
//   Heather plays the file "heather_sunrise.wav" at sunrise/sunset.
//   Heather plays the file "heather_noon.wav" at solar noon or moon transit.
//
//   If the sun/moon files are enabled a double musical note appears next to
//   the rise/noon times.  Otherwise, the horizon type letter is used.  The
//   horizon type always appears next to the set time.
//
//   The standard rise/set sound is a rooster crowing and the noon sound is
//   a church bell.  
//
//   If moon rise/set times are selected (TRM) the sound files are played at 
//   moon rise/transit/set and not sun rise/noon/set.  They are the same files
//   used for sun times... there are not any separate moon files.
//
//
//   Normally Heather assumes that the GPS receiver is at a fixed position
//   and the sun/moon rise/set times are only recalculated when Heather
//   starts up or once per hour at xx:00:26 local time.  If you are 
//   working with a moving receiver you can cause Heather to continuously 
//   recalculate the times:
//      Include an "!" after the command.
//         TR C!
//         /sr=c!  
//
//   You can use both "*" and "!" on the same command.
//
//
//
//
//
//-THE PLOT WINDOW
//
//   The receiver data gathered by Heather and stored in the plot queue
//   is shown in the plot window at the bottom of the screen.  The data
//   that is stored and shown is dependent upon the receiver type.
//
//   The plot area is divided into a header area at the top and a plot
//   grid below it.  The header shows the various plot scale factors and
//   reference (center line) values along with a statistical value for each  
//   plot. 
//
//   Clicking on the plot header area will zoom the plot display to full
//   screen Cicking on the zoomed plot header area will restore the screen 
//   to its previous state. 
//   Note that short clicks might be ignored... particularly on devices
//   like UCCM receivers that only output time updates every two seconds.
//   It can help to hold down the mouse button until the screen changes.
//
//
//   Moving the mouse cursor into the plot area will show the values of
//   the data points at the cursor and the time that the value was acquired.
//   Also the time interval from the first point shown in the plot area
//   to the mouse cursor is shown.
//
//   If a plot has not been enabled, its header entry will not be shown.
//
//   You can disable all plots with the G- keyboard command.  Disabling all
//   plots with G- makes it easier to enable just the plots that you want 
//   to see.  
//
//   You can enable all plots that have varying data within the plot view 
//   window with with the G+ keyboard command.  Emabling all plots can 
//   produce a very crowded and confusing display.  
//
//   You can put a title string at the bottom of the plot window with the
//   keyboard command:
//      GG  - label the plot window with a title.
//      Titles are also saved to/loaded from log file comments.  
//
//      If a plot title contains an '&&' then the '&&' is replaced
//      with the current oscillator disciplining parameters. 
//
//      If a plot title contains an '&t' then the '&t' is replaced
//      with the current time
//
//      If a plot title contains an '&d' then the '&d' is replaced
//      with the current date
//
//      If a plot title begins with "&1", "&2", "&3", "&4", "&5", "&6" or &7
//      then the following text will be used as extra title lines positioned
//      above the main title.  Note that the GR screen redraw command will 
//      erase the extra titles.
//
//      If a plot title begins with "&b" then the following text will be
//      placed in the program window title bar.
//
//      You can also set the program title bar with the /pt=string
//      command line option.  If you want to include any spaces in the
//      program title bar, replace them with the '_' character.  If the title
//      bar string is empty,  Heather uses the receiver type as the title.
//
//
//   Heather also uses the plot title feature for displaying things like
//   calendar events, errors, and certain status information.  Setting a user
//   defined title usually inhibits these automatic titles.
//
//   Heather usually only updates the parts of the screen that have changed. 
//   You can force Heather to fully redraw the screen from the keyboard:
//      GR  - redraw the screen
//   Doing a GR will erase any "extra" title lines.
//
//
//   You can zoom the plot window display to full screen:
//      ZP   - zoom the plot window to full screen
//             Clicking the mouse/touchscreen in the upper right corner of
//             the zoomed plot takes the display out of "plot review" mode
//             just like you pressed the DEL key (but without exiting zoomed
//             plot mode)
//      Clicking on the text above the title bar with also zoom the plot
//      area to full screen.
//
//
//   Data plots can be individually configured for either fixed scale factors
//   or can be automatically scaled. Most plots default to be automatically
//   scaled and centered to fit the plot window.
//
//   If a plot has a fixed scale factor, the plot is labeled like:
//       DAC=(25 uV/div)
//
//   An automatically scaled plot is labeled like:
//       DAC~(25 uV/div)
//   Also, if auto-scaling is enabled, moving the mouse pointer into the
//
//
//
//   The "reference" value for a plot is the value at the horizontal center
//   line of the plot area (indicated by small '<' and '>' marks at the left
//   and right edges of the plot area.
//
//   Plots can be individually configured for either fixed reference
//   values or can have a "floating" reference value where the plot is
//   automatically centered in the plot area.
//
//   If a plot has a fixed reference value, the plot is labeled like:
//       ref=<100 uV)
//
//   A plot with a floating (auto centered) reference value is labeled like:
//       ref~<100 uV>
//
//
//
//   The plot grid is divided into horizonal and vertical major divisions
//   which are further divided into minor divisions.  Time is represented by
//   the horizontal axis and data values by the vertical axis.
//
//
//
//   The "V" (view) keyboard command controls the view window into the plot
//   data queue.  This sets how much data is shown in the plots.  The
//   view value can be either in minutes per (major) division or the time
//   interval to be shown.  Note that the specified view interval is 
//   automatically tweaked/rounded to fit a multiple of the plot grid size.
//
//   If the selected plot view interval is larger than one plot queue sample
//   per pixel, the plot queue data is down-scaled by dropping values.
//   Note that if down-scaling is in use the display of time skip markers, etc 
//   may not be accurate / complete.  Markers or other events that do not 
//   happen on a displayed sample may not always be shown because all 
//   non-displayed  samples are skipped over while processing the plot queue 
//   data for display.  Setting the display filter to a negative value like
//      FD -1
//   or to positive values greater than (VIEW_TIME/PLOT_WIDTH) will average
//   together all polot queue entries covered by the each displayed pixel
//   and avoid dropping any missing events.
//
//
//      VA  - shows all data currently in the plot queue.  The plot horizontal
//            scale factor (time per division) is adjusted to fit the data
//            onto the screen. The data is down-scaled by dropping values.
//
//      VT  - auto scale the time axis as data comes in.  The plot view 
//            interval is automatically adjusted as data come in.  Once the
//            plot window fills, it is scrolled left a few major divisions
//            and a new scale factor is calculated.
//
//            You can force startup in VT mode with the /va command line
//            option.  Doing this has a side effect of not being able
//            to automatically cancel "View Auto" mode whenever the data
//            queues are cleared or reconfigured.  This might cause some
//            problems.  You can cancel this side effect by doing a VA or V0
//            keyboard command.
//
//      V#  - set the plot time to # minutes per horizonal major division
//
//      V#S - set the plot horizontal scale factor so that # seconds of
//            data are shown
//
//      V#M - set the plot horizontal scale factor so that # minutes of
//            data are shown
//
//      V#H - set the plot horizontal scale factor so that # hours of
//            data are shown
//
//      V#D - set the plot horizontal scale factor so that # days of
//            data are shown
//
//      V#W - set the plot horizontal scale factor so that # weeks of
//            data are shown
//
//      X   - set the plot scale factor to 1 hour per division
//
//      Y   - set the plot scale factor so around 24 hours of data are shown
//            If the plot area is being shared with a map display (GB command)
//            this "day" plot view time may be reduced to less than 24 hours.
//
//
//      You can also set the plot view time with the /y command line option:
//         /y=3  - set view to 3 minutes per division
//         /y=3h - set view to 3 hours (can also use #S, #M, #D, #W as
//                 described above for seconds, minutes, days, and weeks)
//         /y    - set the view interval to 24 hour mode
//
//
//   Normally the plots show the last data acquired and scroll to the left
//   as new data comes in.  You can "review" older data using keyboard commands
//   to change the starting point in the plot.  When you are in plot review
//   mode the plot header shows:
//       "Review (DEL to stop):"  or "All (DEL to stop):"  
//   and scrolling of the plot data caused by new incoming data is inhibited.
//
//
//      HOME  - move to the start (oldest) of the plot queue data
//      END   - move to the end (newest) of the plot queue data
//      LEFT  - move the plot forward one horizontal division
//      RIGHT - move the plot back one horizontal division
//      PG UP - move the plot forward one screen
//      PG DN - move the plot back one screen
//      UP    - move the plot forward one hour
//      DN    - move the plot back one hour
//      >     - move the plot forward one day
//      <     - move the plot back one day
//      ]     - move the plot forward one pixel (*)
//      [     - move the plot back one pixel (*)
//      DEL   - exit plot review mode and return to normal scrolling
//
//   (*) If the last keyboard command was an ADEV related command:
//      ]     - scrolls the ADEV plots and tables forward one bin
//      [     - scrolls the ADEV plots and tables backward one bin
//      >     - scrolls the ADEV plots and tables forward one bin
//      <     - scrolls the ADEV plots and tables backward one bin
//      HOME  - move to the start of the adev data
//      END   - move to the end of the adev data
//      LEFT  - move 5 bins forward
//      RIGHT - move 5 bins back
//      UP    - move 10 bins forward
//      RIGHT - move 10bins back
//      PG UP - move one page forward
//      PG DN - move one page back
//
//   You can force ADEV review mode with A ESC.  In ADEV review mode the
//   ADEV type in the ADEV tables is followed by a up/down arrow character
//
//   You can force PLOT review mode with G ESC.  In PLOT review mode the
//   ADEV type in the ADEV tables is followed by a ':' character.
//
//
//
//   If you are in VIEW ALL mode and click the LEFT mouse button at a point in 
//   the plot, the plot will be centered at that point and the view interval
//   will be set to 1 minute per division.  The clicked point will be marked
//   with a "v" at the top of the plot area and a '^' at the bottom.  You can
//   return to the marked point by pressing '0' or '@'.
//
//   When in "auto" or "all" mode, clicking on the plot to zoom in to a point 
//   on the plot will cancel that mode and set normal PLOT REVIEW mode.
//
//   If you (QUICKLY) right click on the graph it will mark the point
//   and center the display on it (without zooming).  You
//   can return to the mark with the '@' or '0' keyboard command.
//
//   You can hold the RIGHT mouse button to scroll around in the plot.  Move
//   the mouse cursor to the horizontal center of the plot and HOLD the right
//   button down.  Moving the mouse cursor to the left or right of the plot
//   center scrolls the plot in that direction.  The further you move the
//   mouse from the center of the plot, the faster the plot will scroll.
//
//
//   You can disable the mouse:
//      /km  - toggle the mouse functionality
//
//
//   You can disable the keyboard from the command line.  The only ways to
//   exit Heather when the keyboard is disabled is to click the CLOSE button
//   on the operating system title bar (or using the "kill process" command
//   of your operating system) or you can use the "ESC y" command.  The
//   "ESC !" keyboard command will re-enable the keyboard.  If you press any
//   key while the keyboard is disable a beep will sound.
//      /kq  - toggle the keyboard enable  (earlier version of Heather used
//             /kk for this, but that conflicted with the temperature control
//             PID commands)
//
//
//
//   PLOT MARKERS
//
//      If you see something interesting a a plot, you can set a marker at that
//      point.  Move the mouse cursor to that point and press "=".  A numeric
//      marker (from 1 to 9) will show at the top of the plot area.
//
//      To center the plot on a marker, press that number on the keyboard.
//      Pressing '0' or '@' centers the plot on the last place you 
//      left-clicked in the plot area.
//
//      If you have just gone to a marker, pressing '+' will center the plot 
//      where where the cursor was previously located.
//
//      To delete a marker, select that marker from the keyboard and press '-'
//      The GU keyboard command will clear all plot markers.
//
//      Note that the "+" and "-" keyboard commands have a different meaning
//      if you have not just selected a marker... they move the last selected
//      plot up or down and lock the plot scale factors and reference line
//      value (see the description below).
//
//      Plot markers are also saved in and reloaded from log files.
//
//
//   TIME SEQUENCE and HOLDOVER ERRORS
//
//      Heather expects to see a time message from the GPS device every
//      second.  The time code in the message should always increment
//      by one second.  If an error is detected in the time code sequence
//      (like skipped or duplicated time codes) these are flagged by a 
//      RED tick mark at the top of the plot and the line that shows the
//      time is drawn in RED (instead of CYAN).  If you place the mouse cursor
//      in the plot area and press '%' the plot will jump to the next time
//      sequence error.
//         GE  - toggles display and finding of time skip markers
//         /ge - toggles display and finding of time skip markers
//
//      If a GPSDO enters a holdover state that is indicated by a solid RED
//      line at the top of the plot area.  The '%' key will also move the plot
//      display to the next holdover event.
//         GH  - toggles display and finding holdover events
//         /gh - toggles display and finding holdover events
//
//
//   CONTROLLING THE DISPLAYED PLOTS
//
//      The "G" keyboard menu controls the plots that are displayed and their
//      configuration.
//
//   These are the standard plot assignments.  Some devices may use the
//   various plots for other purposes.  The G keyboard menu will show what
//   info is assigned to the various plots for that device.
//
//        GP - usually a "PPS" (Pulse Per Second) output related value
//             (TAPR TICC chA Time Interval Error)
//        GO - usually an oscillator frequency output related value
//             (TAPR TICC chB Time Interval Error)
//        GO - usually an EFC DAC or PPS sawtooth correction related value
//        GT - usually a temperature related value
//        GD - GPSDO EFC DAC value or GPS receiver sawtooth value
//             (TAPR TICC debug mode chA FUDGE value).  Depending upon the
//             receiver type the DAC value is either a voltage or a
//             percentage from (-100% to +100% of full scale with 0% being
//             the center of the control range).  The RFTG DAC range is
//             0% .. 100%
//
//        G1 - receiver latitude
//             (TAPR TICC/counter channel A phase value)
//        G2 - receiver longitude
//             (TAPR TICC/counter channel B phase value)
//        G3 - receiver altitude
//             (TAPR TICC/counter channel C phase value)
//        G4 - receiver speed  or TFOM (time figure of merit)
//             (TAPR TICC/counter channel C phase value)
//        G5 - receiver course or FFOM (frequency figure of merit)
//             (TAPR TICC debug mode chA TIME2 value)
//
//             Note: the G4 (speed) and G5 (course) selections don't appear
//                   in the "G" keyboard menu, but do work for receivers that
//                   output heading and speed info.
//
//        G6 - average DOP (dilution of precision) value
//             (TAPR TICC debug mode chB TIME2 value)
//        G7 - the TAPR TICC channel C Time Interval Error data
//        G8 - the TAPR TICC channel D Time Interval Error data
//
//        G9 - message timing offset
//        G0 - message timing jitter
//
//        GA - ADEV plots (see the section of ADEVs)
//
//        G$ - tracked satellite count
//
//
//   The GKx commands control plotting of four different plots. Which data
//   that is being plottted depends upon the device type and which options
//   have been selected:
//
//   If an external enviromental sensor is active the tide plots and sat 
//   az/el/signal level plots are not available.
//   These commands control the environmental sensor plots:
//        GKA - toggles display of all the environmenal sensor plots
//        GKH - controls humidity sensor plot
//        GKP - controls air pressure sensor plot
//        GKT - controls first temperatue sensor plot
//        GKU - controls second temperatue sensor plot
//
//   If plotting a satellite az/el/signal level is enabled (SQ command):
//        GKA - toggles display of all sat PRN related plots:
//        GKZ - controls azimuth plot
//        GKE - controls elevation plot
//        GKS - controls signal level plot
//        GKG - controls the carrier phase / pseudorange / gravity plot
//              Carrier phase is plotted if available, else the pseudorange
//              is plotted.  If neither carrier phase or pseudorange is 
//              available the plot defaults to the gravity offset plot.
//   
//   Otherwise:
//        GKA - toggles display of all the solid earth tide and gravity plots
//               (except for HP5071 cesium beam oscillator devices which uses
//                the eath tide plot queue data entries for other things)
//        GKX - controls longitude earth tide plot
//        GKY - controls latitude earth tide plot
//        GKZ - controls altitude earth tide plot
//        GKG - controls vertical gravity offset plot
//
//
//   Selecting one of the plots listed above brings up a sub-menu of options
//   for controlling that plot.  The descriptions listed below use the "GP"
//   plot, but can be used with any of the plots.  Replace the lower-case "p"
//   shown below with the letter or number of the plot you want to manipulate.
//
//        Gp<cr> - toggles the plot display ON or OFF
//        Gpp    - toggles the plot display ON or OFF
//        /gP    - from the command line - toggles plot "P" ON or OFF
//
//        If the previous key was not a plot marker command (where
//        a following + or - key will undo a marker)  you can
//        use the '+' or '-' keys to move the last selected
//        graph up or down 0.1 divisions.   That graph's scale
//        factor and center reference values will be "fixed".
//
//           +     move the last selected plot up 0.1 major divisions
//           -     move the last selected plot down 0.1 major divisions
//
//
//        GpI    - toggles inversion of the plots' display.
//                 Inverting a plot can make it easier to compare how one 
//                 parameter (like temperature) affects another one (like 
//                 DAC voltage)
//        /mi    - invert PPS and TEMPerature plots
//
//
//        Gp/ - select plot statistic selection menu. Heather can calculate
//              various statistics of the plot data shown in the plot window:
//           Gp/A   - average value
//           Gp/R   - RMS value
//           Gp/S   - standard deviation
//           Gp/V   - variation
//           Gp/N   - minimum value
//           Gp/X   - maximum value
//           Gp/P   - span - difference between maximum and minimum values
//           Gp<cr> - turns off the plots' statistic display
//           Gp/?   - toggles showing all 7 statistics for a selected plot.
//                    The values are shown as "debug" info in the plot area.
//
//        G/p  - you can set the statistic to show for ALL enabled plots
//               with this command
//
//        GpA  - toggles auto-scaling mode for ALL plots
//        /ma  - from the command line
//
//        GpC  - select the color to display the plot in
//
//        GpD  - show the derivative of the plot data.  When a plot is in
//               derivative mode, the ':' after the plot statistics type
//               is changed to an '*'.  Showing the derivative of a plot can
//               be useful for finding glitches and spikes in the data.
//
//        GpL  - toggles a linear regression trend line for the plot.  The 
//               trend line is drawn and its equation (as a function of time)
//               and extrapolated 24 hour change is shown as the plot title.  
//               If the selected plot has the "derivative (*)" or "frequency 
//               (#)" modifier set, the trend line cannot be plotted.  The 
//               trend line equation of the un-modfied plot data is shown, 
//               though.
//
//               The trend line equation title also shows the extrapolated
//               trend value over (drift) 24-bours (default).  The OX obscure
//               keyboard option command allows you to change the extrapolation
//               period:
//                  OX0 - 24 hours
//                  OX1 - 1 hour
//                  OX2 - 1 minute
//                  OX3 - 1 second
//
//        Gp=  - removes drift from a plot by subtracting the linear regression  
//               trend line slope from the plot.  To cancel trend removal,
//               enter a value of 0.  In trend removal mode the ':' after
//               the plot statistics value is replaced by an '='.
//
//        GpS  - set the plot scale factor in units per division  -or-
//               enable auto scaling of the plot.
//        /mP     - from command line doubles plot P scale factor
//        /mP=val - sets plot P scale factor from the command line (0 = auto)
//        /m      - doubles all plot scale factors from the command line
//        /m=val  - multiplies all plot scale factors by "val"
//
//        GpX  - toggles auto-scale mode for the selected plot
//
//        GpZ  - set the plot zero reference value (the value at the horizontal
//               center line of the plot) to a fixed value  -or=  enable auto
//               centering of the plot.
//        /zp      - toggles plot P auto-centering from the command line
//        /zp=val  - sets plot P zero reference line value the command line
//                   (0 = auto center).  "p" can be any plot selection
//                   character.
//
//        GpF  - calculate an FFT (Fast Fourier Transform) of the selected
//               plots' data.
//
//                 The data to be analyzed starts at the beginning of
//                 the plot window and end when the max fft size points
//                 or the end of the plot data are reached.  The
//                 data is sampled from the plot data at the viewing
//                 interval (seconds/pixel). 
//
//                 The calculated FFT bins are shown as seconds with the
//                 lowest frequencies to the left and highest to the right.
//                 Moving the mouse cursor within the plot area shows the
//                 various FFT bin values.
//
//                 The max FFT size is set by the /qf[=#] command line option.
//                 (1024 points... if not given then /qf is 4096 points,
//                 otherwise it is whatever is set (must be a power of 2). If
//                 the number of data points in the plot queue to less than
//                 the FFT size, the FFT size is reduced accordingly.
//
//                 Note that a FFT requires the input data to be bandwidth
//                 limited to below the sample frequency or else you will.  
//                 get spurious values due to aliasing.  Set the display
//                 display filter count to at least the value shown as
//                 the "view interval" in minutes/division.
//
//                 The FFT plot option defaults to doing a single
//                 FFT of the selected plots' data when the FFT command was
//                 given.  The O L keyboard command can be used
//                 to enable a "live" FFT that gets recalculated
//                 every time a new point is added to the plot.
//
//                 The O D keyboard option toggles the FFT display value
//                 format between raw values (default) and dB's.
//
//                 Whenever an FFT is calculated, the first point of the plot
//                 queue data analyzed by the FFT is marked with MARKER 1 and 
//                 the last point is marked with MARKER 2.
//
//
//        GpH  - calculates a histogram of the currently displayed plot
//               queue data.  The histogram and FFT options share the
//               the plot same display code and cannot be used at the same
//               time.
//
//
//        GF   - toggle the FFT or histogram plot display on and off.
//               If the debug log file is open then whenever a FFT or
//               histogram plot is toggled on the current histogram or 
//               FFT data is written to the debug file.
//
//        Note:  Histograms and the FFT use a lot of the same code.  You
//               cannot enable both a FFT and histogram at the same time.
//               You can only show histograms or FFTs for one plot at a
//               time.  You turn off a histogram with the GF command (the
//               G menu always shows F)FT for the GF command, even though it
//               can turn off the histogram plot.
//
//
//        Gp~  - applies a deglitch filter to the selected plot. The filter
//               prompts for a "sigma" value and replaces any point in the
//               plot that is more than "sigma" standard deviations away from
//               the average plot value with the previous point.  To remove 
//               glitches from all plots, use the CG command.
//
//        Gp#  - for time interval counters, shows the selected plot's TIE
//               (time interval error) value as frequency.  This also works
//               for the PRS-10 FC (frequency control) plot to show the value
//               in Hz instead of PPT (parts per trillion).
//
//        GCG  - controls the tracked satellite count plot.
//               The satellite count plot is shown in CYAN at the bottom of
//               the plot window (each minor division equals one satellite)
//        /g$  - from the command line
//
//
//      You can apply an averaging filter to the displayed plots (see the
//      description on the /fd command in the FILTERS section for more details.
//         FD  -  set the display filter count.
//
//
//      Normally Heather displays the OSC related parameter values in ppb
//      (parts-per-billion) or ppt (parts-per-trillion) which can cause 
//      Europeans to wander off in a daze of confusion and angst.
//      You can display the OSC related value with an exponent using:
//         /tx - toggle OSC value displays with eXponent
//
//
//
//   PATCHING GLITCHES IN THE PLOT DATA
//
//      Occasionally you may have a data glitch in the acquired plot
//      data.  Heather allows you to patch a glitched data value.
//
//      Carefully position the mouse cursor on the leading edge of the 
//      offending point and press '~'  This will replace the point's data 
//      with the previous data point.  Ideally you should have the display
//      filter (FD command) turned off and the view interval (V command) set
//      to one point per pixel (V 0) when patching data glitches.
//
//      If the mouse cursor is not in the plot area and over a data point 
//      you will hear a warning BEEP.
//
//      Each time you press '~' the glitch edit point (but not the mouse
//      cursor) is incremented to the next point.  You can press '~' multiple 
//      times to remove a wider data glitch as long as the mouse does not 
//      move (by even a single pixel).  Whenever the mouse moves, the glitch 
//      edit point changes to the new mouse position.
//
//      You may want to then use the CR command to recalculate xDEV
//      and MTIE values.
//
//      After patching up a plot glitch you can use the CR command to 
//      recalculate xDEV and MTIE data.
//
//
//      Heather can also automatically remove all glitches from a plot with
//      the Gp~ command (where 'p' is the plot to deglitch).
//        Gp~  - applies a deglitch filter to the selected plot. The filter
//               prompts for a "sigma" value and replaces any point in the
//               plot that is more than sigma standard deviations away from
//               the average with the previous point.
//
//      The CG command will remove glitches from all plots.  
//
//      The Gp~ and CG deglitch commands work on the data interval in the 
//      plot queue that is currently being displayed.  To deglitch all the 
//      data in the plot queue, use the VA command first to display all 
//      the plot queue data.  The way these commands work is ineffective
//      when removing a glitch at the first point in the viewed plot area.
//
//      One way to remove glitches at the start of the plot area is to use
//      the CT command:
//
//        The CT command will trim (delete) all plot queue entries before 
//        the first entry shown in the plot area or after the last one.
//
//        This can be a useful alternative to using the CP or CC commands 
//        that clear all data from the plot queue if you want to remove 
//        garbage data from the plot queue that can occur when the program 
//        first starts capturing data from the receiver.  You may need to 
//        follow the CT command with the CR command to recalulate ADEVs 
//        from the remaining data in the plot queue.
//
//        To delete data at the start of the plot queue first position the 
//        plot view so the first entry you want to keep is at the left edge
//        of the plot window.  Then enter CTS and  all previous entries will 
//        be deleted.  
//
//        To delete data at the end of the plot queue first position the 
//        plot view so the last desired entry is at the right edge of the
//        plot window and enter CTE and all the following entries will be
//        deleted.
//
//        To delete data that is not shown in the plot window,  adjust the plot
//        view to show all the data you want to keep.  Then enter CTSE and all
//        data not shown in the plot window will be deleted.
//
//        After entering a "CT" command, the plot view will be set to "view all"
//        just like you entered "VA".
//
//      There is no way to un-do a glitch removal or plot queue trim.
//
//
//
//
//   TEMPERATURE DISPLAYS
//
//      Lady Heather can display the temperature readings in several
//      different temperature scales (I bet you didn't know there are 
//      so many!) by using one of the following command line options:
//
//           /tc    - show Celcius temperatures (default)
//           /td    - show DeLisle temperatures
//           /te    - show Reaumur temperatures
//           /tf    - show Fahrenheit temperatures
//           /tk    - show Kelvin temperatures
//           /tn    - show Newton temperatures
//           /to    - show Romer temperatures
//           /tph   - show Paris Hilton temperatures - at 20C Paris is
//                    assumed to be nominally clothed (yeah, right).  Every
//                    10C above that she sheds a layer of clothing.  Below 
//                    that she adds one.  Degrees H indicates how hot Paris 
//                    Hilton actually is (or thinks she is).
//           /tr    - show Rankine temperatures
//           /ty=#  - show temperatures to # decimal places
//
//
//
//
//
//-WRITING SCREEN DUMPS
//
//   Heather can write .GIF or .BMP image files of either the entire screen
//   or just the plot area.  Dumps can be either as the screen appears or
//   in "reverse video" where BLACK and WHITE are swapped.  Reverse video
//   dumps are useful for printing.
//  
//     WS  - write screen to image file
//     WR  - write reverse video screen to image file
//
//     WG  - write plot (graph) area of the screen to image file
//     WI  - write reverse video plot (graph) area of the screen to image file
//
//   You get a beep at the start and end of the dump.  
//
//     
//   The '\' keyboard command can be used to do a quick full screen .GIF dump
//   with a single keystroke.  It does not bring up a menu that prompts for a 
//   file name.  This can be useful because redrawing of the plot area after 
//   entering the file name from the normal screen dump menu can cause
//   problems with some parts of the screen not being updated before the 
//   screen dump happens. The "quick" screen dump is done to file
//     "xxxxx.gif"
//   where "xxxxx" is dependent upon the receiver type.
//
//   You can also force a screen dump by left-clicking on the screen where
//   the "Receiver data" info is near the upper left hand corner of the
//   screen.  This is handy if you are using a touch-screen.
//
//
//   If you start to select a reverse video screen dump (even if you do not 
//   complete it by using the ESC key) the reverse video attribute will 
//   will be used for any following '\' initiated screen dumps. The same 
//   applies to normal polarity screen dumps.
//
//   If the mouse cursor is in the plot area when a screen dump is done, an
//   "X" will be drawn in the plot area of the dump.
//
//
//
//
//
//-GPSDO and HOLDOVER CONFIGURATION
//
//   GPS Disciplined Oscillators (GPSDOs) use the GPS satellite signals to 
//   steer a precision oscillator to a precise frequency (usually 10.0 MHz) 
//   over long periods of time.  This "discipling" process corrects for normal 
//   oscillator frequency drift, aging, and temperature effects.  
//
//   The steering of the oscillator frequency is usually done by a phase
//   locked loop (PLL) circuit in the GPSDO that compares the current frequency 
//   to the GPS timing signals.  A GPSDO controls the oscillator frequency by 
//   using a digital to analog converter (DAC) to drive the oscillator's 
//   electronic frequency control (EFC) signal.  
//
//   If a GPSDO loses lock on the GPS satellites it can enter a HOLDOVER mode
//   where it attempts to guess the compensation that it needs to apply to the
//   oscillator in order to keep it on frequency.  Many GPSDOs can be 
//   forced into HOLDOVER mode manually by the user for testing, etc. 
//
//   Heather has some keyboard commands for controlling holdover mode and 
//   oscillator disciplining:
//    
//      HE - enable manual holdover (for the PRS-10 this enables 1PPS input
//           discipling mode - the same as the DE command)
//      HX - exit manual holdover (for the PRS-10 this disables the 1PPS
//           input discipling mode - the same as the DD command)
//      HH - toggle holdover mode (discipling on the PRS-10) on/off
//
//
//   Besides HOLDOVER mode, some GPSDOs and the PRS-10 rubidium oscillator
//   let the user manually control the oscillator EFC signal or turn ON/OFF  
//   oscillator discipling.
//
//      DD - completely disable oscillator disciplining
//      DE - re-enable oscillator disciplining
//      DS - set the oscillator EFC DAC to a given value.
//
//
//   The plot area normally shows when the device is in holdover by a RED 
//   line at the top of the plot. You can turn this off with:
//      GH  - from the keyboard toggles the holdover plot display
//      /gh - command line option toggles display of holdover events
//            in the plot area.
//
//
//   Heather shows the amount of time of the current or last holdover event.
//   The value is shown in GREEN if the holdover event ended before Heather 
//   was started. It is shown in YELLOW if a holdover event occured after 
//   Heather was started.  It is shown in RED if holdover mode is currently 
//   active.
//
//
//
//  GPSDO DISCUPLINING CONFIGURATION PARAMETERS:
//
//     Some GPSDOs let the user configure various parameters of the oscillator
//     disciplining PLL system.
//
//     GPSDO control parameters are accessible from the "&" keyboard menu.
//     Not all GPSDOs support all of these settings.
//
//     The "&" keyboard command brings up the oscillator parameter
//     and satellite max signal level display screens.
//     To return to normal display mode you can press SPACE
//     or ESC or "&" again.
//
//     The "&" display screen shows the current GPSDO parameters and also
//     a table of the maximum signal level seen from each satellite.
//
//       &d  - sets the PLL damping factor
//       &t  - sets the PLL time constant
//       &g  - sets the PLL gain (i.e. Hz change per volt of EFC) 
//       &p  - sets the pullin range (for UCCM devices)
//
//       &i  - sets the DAC initial voltage
//       &n  - sets the DAC minimum voltage
//       &x  - sets the DAC maximum voltage
//
//       &h  - sets the DAC allowable range high value
//       &l  - sets the DAC allowable range low value
//
//       &f  - sets the max frequency offset threshold
//       &j  - sets the jam sync threshold
//
//       &a  - autotune oscillator parameters
//
//
//     Some GPSDOs (like the Nortel/Trimble NTBW and NTPx devices) let the user
//     control the GPSDO settings, but do not save them in EEPROM.  You can 
//     cause Heather to configure the GPSDO at startup with these command 
//     line options:
//
//       /ud=val - set oscillator disciplining damping value
//       /ut=val - set oscillator disciplining time constant value
//       /ug=val - set oscillator disciplining gain value
//       /up=val - set pull-in range value (for UCCM devices)
//       /ui=val - set oscillator disciplining initial dac value
//       /un=val - set oscillator disciplining minimum dac value
//       /ux=val - set oscillator disciplining maximum dac value
//       /uh=val - sets the DAC allowable range high value
//       /ul=val - sets the DAC allowable range low value
//
//       The &L (/ul) and &H (/uh) commands use an undocumented TSIP command
//       for reading and setting the what appears to be the allowable EFC DAC.
//       range.  You can alter the low and high values with the UNDOCUMENTED
//       &L and &H keyboard commands.  These values might just be for reporting 
//       the allowable DAC range to the software or they might do something 
//       else!  Also, /ul and /uh on the command line may not always work... 
//       it seems to work from the keyboard, though.
//
//                  CAVEAT EMPTOR IF YOU USE/CHANGE THEM!
//
//
//     When you write a log file an OSC_GAIN comment is written to the log 
//     file.  This allows the computation of osc drift and tempco from logged 
//     data acquired on a unit that does not have the same osc gain (or that 
//     is not connected to a tbolt).  If the osc gain has been loaded from a 
//     log file,  it is shown in YELLOW.
//
//
//
//  OSCILLATOR DRIFT RATE and TEMPERATURE COEFFICIENT VALUES
//
//     For Trimble GPSDO devices, the '&' screen display shows an oscillator 
//     drift rate and temperature coefficient value.  These are calculated 
//     from the data points shown in the plot window.
//
//     For the best results,  select a plot display interval
//     that covers a fairly long time interval with well 
//     behaved DAC and/or TEMP values.  
//
//     You should be able to get a decent value for the drift rate 
//     with 24 hours of data. The oscillator drift rate value makes the most 
//     sense if the temperature is stable so that temperature effects on the 
//     oscillator frequency are minimized.
//
//     The oscillator temperature coefficient value makes the most sense if 
//     the temperature is allowed to change in a linear ramp.  This is
//     easy to achieve with Heather's active temperature control mechanism.
//
//
//
//  AUTOMATICALLY SETTING GPSDO OSCILLATOR PARAMETERS:
//
//     Heather can automatically configure Thunderbolt style GPSDO parameters 
//     to values better suited for precision time and frequency applications
//     that their default "telecom" values.
//
//     The "&a" keyboard command sequence starts the "auto-tune" process.
//
//     Before running auto-tune on the Thunderbolt you should: 
//        1) Wait for the unit to stabilize with (relatively) 
//        steady DAC, OSC, PPS, and temperaure values. Overnight is good.
//
//        2) Set your antenna elevation mask angle (F E keyboard command) 
//        to 0 and signal level mask (F L keyboard command) to 1.  This allows
//        collection of signal level data across the full sky.
//
//        3) Clear your signal level history (C M keyboard command)
//
//        4) Let Heather run for at least 6-12 hours to build
//        up a new satellite signal level map.
//
//        5) Issue the "&a" auto-tune command and wait for it to
//        complete
//
//     Heather will spend a couple of minutes tickling
//     your oscillator and determine good values for the
//     osc gain and initial dac voltage.  The time constant
//     will be set to 500 seconds,  and the damping to 1.0
//     Also the AMU (signal level) mask will be set to 1.0
//     and the satellite elevation mask to midway between the horizon 
//     and where your average signal level begins to fall off.
//
//     The values will be written to the configuration EEPROM.
//     You can then manually change any of the parameters
//     that may not suit your needs.
//
//     Note that non-Thunderbolt GPSDOs (such as the NTBW and NTPx telecom
//     devices) do not all support saving disciplining parameters to EEPROM 
//     and some do not allow users to change the disciplining parameters.
//     You can use "/d" command line options for setting the PLL parameters
//     from the command line.
//
//     If you run the auto-tune command on non-Thunderbolt GPSDO devices then
//     only the satellite elevation mask (and perhaps the signal level mask)
//     values will be set.
//
//     You can erase the auto-tune results message in the plot title using
//     the "GG" keyboard command.
//
//
//
//     For the Symmetricom rubidium oscillators (X72, X99, SA22) the &a 
//     command calculates and sets the DDS tuning word that sets the 
//     oscillator output frequency (DDS).  Before issuing the "&a" command you
//     should have a stable 1PPS signal connected to the PPS input and wait
//     for the device to stabilize (recommend at least 24 hours of power on).
//
//     The &a command will prompt for the number of seconds of data to analyze
//     to determine the device drift rate... the longer the better.  The
//     minimum time is 600,  the default is 1800 seconds.  Several hours is
//     better.  First the DDS word is set to 0 and the TIC offset register 
//     is set to zero out the current 1PPS offset.  Next data is collected 
//     for the specified number of seconds.  Finally, the data is analyzed 
//     by calculating a linear regression trend line and the DDS tuning word 
//     is set and the TIC offset value is re-zeroed.
//
//     After the auto-tune interval has been reached, Heather will set the
//     DDS tuning word to the calculated value.  On some firmware versions
//     the EE keyboard command can write the tuning word (and maybe the other
//     device configuration values) to EEPROM.  The calculated tuning
//     value will be shown in the plot title line.  You can record that value
//     and use the PZ keyboard command to restore the DDS word if you lose
//     power.  Note that the X72 / SA22 has no way to read back most of the
//     current settings (more ass spanking justified).
//
//     Heather implements a "software eeprom" that records all setting
//     changes in a file (default tbeeprom.dat).  This file is used
//     to restore all the last known settings every time Heather is started.
//     If you have more than one Symmetricom rubidium oscillator, the "/wp="
//     command can be used to change the "tb" prefix string used for the
//     EEPROM file. For example /wp=sa22 will use the file "sa22eeprom.dat".
//     The /wp command also changes the prefix used for automatic log and
//     screen dumps.  When you first setup a X72/SA22 you should set all
//     the device parameters to what you want (even if they appear to 
//     already be set correctly.  This will insure that Heather knows the
//     correct device configuration.
//
//
//
//  ACTIVE GPSDO TEMPERATURE CONTROL
//
//     GPS Disciplined Oscillators are very precise devices and their
//     precise oscillators and circuity can be sensitive to temperature,
//     other environmental conditions (air pressure, humidity, etc), and
//     power.  You can maximize a GPSDOs performance by minimizing changes
//     in these values.
//
//     Heather has the ability to actively control the environmental
//     temperature of GPSDO devices that regularly (like every second) report 
//     their temperature to a high level of resolution (like less than 0.1C).
//     The Trimble Thunderbolt series of devices is particularly good at this.
//     Early models have a temperature sensor with a resolution of around
//     0.01C and later models used an inferior version of the sensor with
//     around 0.1C resolution.
//
//     Heather uses a PID control algorithm driven by the GPSDO temperature
//     sensor readings to PWM (pulse width modulate) a temperature control
//     device (such as a fan or a peltier device).
//
//     You specify the desired control temperature in degrees C.  A value
//     of 0 says to turn off temperature control.
//        TT          - from the keyboard
//        /tt=degrees - from the command line
//
//     When temperature control is activated an DOWN_ARROW, EQUAL_SIGN, or 
//     UP_ARROW is shown next to the temperature reading at the top of the
//     screen.  They mean that the temperature control PID is calling for
//     cooling, holding temperature, or heating.
//
//
//     Normally Heather uses the receiver port RTS and DTR serial port modem 
//     control lines to control the fan or peltier (there is some legacy 
//     code in there that could be activated to work with a parallel port).
//
//     Heather also supports using a dedicated serial port to control the
//     "fan".  This can be enabled with the /ef= command line option.  The
//     "fan" port manipulates the modem control signals just like when using
//     the receiver port.  It also sends ASCII commands (default 115200,8,N,1)
//     out the "fan" port.  Using a dedicated "fan" port can be useful if the
//     receiver port does not support modem control signals (like some USB
//     devices or an Ethernet connection).
//        $INIT<cr><lf> - initialsize the temperature control device
//        $STOP<cr><lf> - disable the device
//        $HOLD<cr><lf> - hold the current state
//        $CTRL msecs<cr><lf> - values to PWM the device with.
//             Positive values indicate heating,  negative indicate cooling
//             The value is in millisecods (can be interpreted as percent*10)
//
//     RTS is the temperature controller enable (+12=off, -12=on)
//     DTR is the heat (-12V) / cool (+12V) line.  
//     (note that some serial ports may have different voltage ranges like
//      +/- 6V)
//
//     The DTR line is updated once a second with a pulse whose width is
//     proportional to how hard to drive the fan/peltier. Use the line to
//     control a transistor or solid state relay.  The RTS line can be
//     used to enable the temperature control device.  RTS and DTR will be 
//     set to +12V when Heather exits.
//
//     Simple implementation:  
//        Isolate the Thunderbolt in a box (I use a corrugated cardboard box),
//        set the control temperature below the typical unit operating temp
//        but above normal room temp.  When Heather signals COOL turn
//        send power to a fan to move room air into the box.  You want the 
//        fan to move enough air to cool the unit,  but not so
//        much air that the temperature drops by more than 0.01C
//        per second.  The indicator of too much airflow is a 
//        temperature curve that spikes down around 0.1C several
//        times per minute.  Too little airflow shows up as a
//        curve that oscillates around 0.25C about set point over
//        a couple of minutes.  Good airflow should show a 
//        temperature curve stable to with 0.01C with a period of
//        between 1 and 3 minutes.   Generally you do not want
//        the fan to blow directly on the unit (mine is surrounded
//        by foam).  You want to gently move air through the 
//        box.  It can help to include a large thermal mass in 
//        the box (I use a 2kg scale weight, other people use water).  
//
//        Placing the GPSDO power supply in the same controlled environment
//        as the GPSDO can improve system performance.  BE AWARE OF WHAT
//        MIGHT HAPPEN IF A POWER SUPPLY OR CONTROL SYSTEM FAULT CAUSES
//        OVERHEATING OR A FIRE!  
//
//        One thing to try is to disable the fan and closely monitor the
//        temperature see how warm the device becomes in the event of a fan 
//        failure. Try and use an enclosure that keeps the maximum device 
//        temperature to safe levels.  An enclosure with too much insulation
//        is not a good thing here...
//
//
//  TUNING THE TEMPERATURE CONTROL PID
//
//     The temperature control PID is adjusted via the "K" keyboard menu or
//     "/k" command line options.  The "K" keyboard menu works a bit
//     differently than the other keyboard menus! It does not bring up any
//     sub-menus.  It brings up an edit line where you enter a command letter
//     optionally followed by command values.  Commands that expect a value
//     (or values) are shown with an "=" sign here.  You do not type the "="
//     sign, just the letter and the value(s) separated by a space or comma.
//
//     From the command line you DO enter the "=" to set a value. For instance
//     you would set the PID parameters with:
//        K 1.5 45 2 100     from the keyboard "K" menu or
//        /kk=1.5,25,2,100   from the command line
//
//
//        A= Autotune temperature PID
//          A 0  - abort autotune
//          A 1  - full autotune with all settling delays
//          A 2  - don't wait for temp to get near the control setpoint
//          A 3  - don't wait for PID to stabilize
//
//        P= PID Proportional (gain) term
//        I= PID Integral control term
//        D= OID Derivative control term
//        F= PID Filter time constant
//        K= P D F I   (sets all foure major PID "K" terms)
//
//        W  config PID with canned slow time constant PID values (default)
//        X  config PID with canned fast time constant PID values
//        Y  config PID with canned very fast time constant PID values
//        N  config PID with canned medium time constant PID values
//
//        G= Scale factor (loop gain correction)
//        H  show PID debug info
//        L= Load disturbance test value
//        O= filter Offset term
//        R= Reset integrator value
//        S= Scale factor (loop\ gain correction)
//           (use /kg= from command line for this since /ks controls sounds!)
//        T= Test PWM output  (cool_msecs, heat_msecs)
//        Z  reset and restart temperature PID control loop
//        9= set auto-tune step size
//        0  test with crude temperature values
//
//
//
//
//   EXPERIMENTAL OSCILLATOR CONTROL PID
//
//     The Thunderbolt GPSDO is a very versatile device that offers the
//     user great flexibility and control.  You can manually control the
//     oscillator EFC DAC and measure the oscillator frequency and PPS error.
//     This provides the ability to implement a user-defined GPSDO control
//     loop.  Lady Heather has an implementation of such a control PID. It
//     is activated from the "B" keyboard command or /x command line options.
//
//     The experimental oscillator control PID commands work like the
//     temperature control PID commands described above.
//
//        K .1 0 100 100     from the keyboard "B" menu or
//        /xk=.1,0,100,100   from the command line
//
//        P= Proportional gain (P)
//        I= Intergral time constant (I)
//        D= Derivative time constant (D)
//        F= Filter time constant (F)
//        K= P D F I   (sets all four PID "B" terms (P D F I))
//
//        N  use pre-configured PID #1 values
//        W  use pre-configured PID #2 values 
//        X  use pre-configured PID #3 values 
//        Y  use pre-configured PID #4 values 
//
//        H  show PID debug info
//        L= Load disturbance test value
//        O= Filter offset
//        Q= Post-filter depth
//        R= Reset integrator
//        S= Scale factor (loop gain compensation)
//        Z  Reset and restart oscillator control PID
//        0  Disable oscillator control PID
//        1  Enable oscillator control PID
//
//
//
//
//
//-GPSDO / TIMING RECEIVER PPS and FREQUENCY OUTPUT CONTROL
//
//   GPS timing receivers and disciplined oscillators usually have one
//   or more timing output signals.  Almost all have a 1 pulse-per-second
//   (PPS) output signal.  On many devices this can be programmed for
//   other frequencies.  Other devices also have other auxiliary output
//   signals that can be controlled.
//
//   The "P" keyboard menu provides commands for controlling these output
//   signals.  The paramters that can be set via the "P" menu depend upon
//   the device type.
//
//
//
//   ANTENNA CABLE DELAY
//
//     To precisely align the PPS output to GPS or UTC time, the receiver
//     needs to know the delay of the GPS signal through the antenna cable
//     (plus the delay through the PPS output cable).  The cable delay 
//     adjustment can also be used to shift the PPS output relative to 
//     GPS/UTC time for other reasons.
//
//     Note that some devices (like the Trimble Thunderbolt and the 
//     OSCILLOQUARTZ STAR) use a NEGATIVE number for compensating for cable 
//     delay compensation, other devices use a  positive number.  Consult 
//     the device manual for details (but good look finding them!)
//     
//        PC         - sets the cable delay
//        /c=75      - sets the cable delay (in nanoseconds) from the command
//                     line
//        /c=50f     - sets the cable delay to 50 feet of 0.66 velocity factor
//                     coaxial cable
//        /c=70m     - sets the cable delay in 70 meters of 0.66 velocity
//                     factor coaxial cable
//        /c=50m,.8v - sets the cable delay to 50 meters of 0.80 velocity 
//                     factorcoaxial cable
//
//     The "PC" keyboard command lets you specify the cable delay in
//     nanoseconds or in cable length / velocity factor:
//       PC 100      - 100 nanoseconds
//       PC 50f      - 50 feet of 0.66 velocity factor coax
//       PC 75m .77v - 75 meters of 0.77 velocity factor coax
//
//     For the SRO100/SRO70 PC sets the clock in the device to the displayed
//     system date/time. Heather does not currently use the date/time info
//     that can be read from the SRO100/SRO70.
//
//
//
//   PPS SIGNAL CONTROL and OUTPUT FREQUENCY CONTROL
//
//      Note that some devices (mostly counters and atomic frequency
//      references) have different meanings for some of these commands. 
//      Check the "P menu on those devices!
//
//      You can turn the PPS signal ON, OFF, or toggle its state:
//        PD   - disable the PPS signal
//        PE   - enable the PPS signal
//        PS   - toggle the PPS signal ON or OFF
//        /pd  - disable PPS output signal from the command line
//        /pe  - enable PPS output signal from the command line
//        /p   - toggle PPS output signal from the command line
//
//        For TAPR TICC devices PE sets the input EDGE select values.
//
//        For the PRS-10 PS sets the magnetic switching mode.
//
//        For the PRS-10 PD sets the 1PPS output offset delay (used to
//        align the 1PPS output to match another device)
//
//        For the SRO100 PD sets the PPS delay.
//        For the SRO100 PS sets the sync mode.
//        For the SRO100 PW sets the PPS pulse width.
//        For the SRO100 PK sets the PPS tracking mode.
//
//        For the SRO100 PC sets the clock in the device to the displayed
//        system date/time.
//
//        For the SRO100 PG sets the "gofast" mode countdown timer.
//        Gofast mode was implemented in device firmware > 1.96.
//
//
//      You can control the PPS signal polarity on some receivers:
//        PR   - select rising edge PPS signal
//        PF   - select falling edge PPS signal
//        PP   - toggle PPS polarity
//        /-   - select rising edge PPS signal from the command line
//        /+   - select falling edge PPS signal from the command line
//
//        For Furuno eSIP devices the PF command is only available in GCLK
//        mode. It is not avaliable in LEGACY clock mode. You can control
//        the clock mode:
//           PG - sets GCLK mode (this has noiser PPS output statistics)
//           PL - sets LEGACY clock mode
//
//        For TAPR TICC devices PF sets the channel "FUDGE" factor
//        delay compensation values.
//
//        For PRS-10 devices PF enables discipling to a 1PPS input with
//        input filtering enabled and PU selects unfiltered 1PPS input.
//        PH configures the 1PPS output to be a static "locked" signal
//        where a high level means locked.  PL selects a low level
//        "locked" indication.
//
//        For PRS-10 devices PA sets the PRS-10 frequency offset using the SF
//        command.  Note that the SF setting is temporary and is reset
//        between device power cycles and resets.  Also, it is not used if
//        the PRS-10 1PPS input is used to discupline the oscillator.
//
//        For PRS-10 devices PY sets the PRS-10 frequency synthesizer control
//        words that allow larger and permanent changes in the output
//        frequency.  There are around 100 valid combinations of synthesizer
//        settings...  see the PRS-10 manual.
//
//        For the SRO100 PR sets the raw phase adjust.
//        For the SRO100 PF sets the frequency adjustment (FC) value.
//        For the SRO100 PH sets the phase comparator offset.
//        For the SRO100 PP does nothing.
//
//
//      The Trimble receivers let you set the oscillator signal polarity
//      reference to the PPS signal:
//        PO   - toggle the oscillator signal polarity from the keyboard
//        /^f  - sync OSC signal falling edge to time
//        /^r  - sync OSC signal rising edge to time
//        /^   - toggle OSC signal edge
//
//
//      Some other devices let you adjust the PPS timing offset in relation 
//      to UTC/GPS time (much like the antenna cable delay parameter). For
//      these devices the PO command is used to set the PPS offset.
//        PO   - set the PPS pulse timing offset in relation to UTC/GPS time
//               (the times are in nanoseconds and can usually be positive or
//                negative)
//
//               For the PRS-10 PO sets the magnetic offset value (used to
//               tweak the output frequency by small amounts)
//
//               For the PRS-10 PT sets the time tag offset offset value
//               (used to adjust the time tag by up to +/- 32767 ns)
//
//               For the X72 PO tells Heather what the master oscillator
//               frequency is (usually 60 MHz)
//
//
//      Some devices let you configure the PPS output between a 1 PPS mode
//      and a PP2S mode (telecom standard pulse per 2 seconds):
//        P1   - select 1 PPS mode
//        P2   - select PP2S mode
//
//      On the Oscilloquartz Star-4 GPSDO:
//        P1   - enable TOD (time of day) output
//        P2   - disable TOD output
//
//
//      Some devices let you reference the PPS pulse to either UTC time or
//      GPS time (and usually this also changes the time reported by the 
//      receiver to GPS or UTC time).  
//        TG   - configure the receiver for GPS time
//        /tg  - configure the receiver for GPS time from the command line
//
//        TU   - configure the receiver for UTC time
//        /tu  - configure the receiver for UTC time from the command line
//
//        TN   - configure the receiver for UTC time with PPS synced to
//               UTC(SU) (ESIP receivers only)
//
//
//
//      Some devices have one or more pulse/frequency output signals that let
//      you set the pulse rate/frequency and/or pulse duty cycle or width:
//        PA   - configure pulse output A
//        PB   - configure pulse output B
//
//        You enter the pulse frequency in Hz and optionally a pulse
//        width or duty cycle (duty cycle values are between 0 and 0.99999,
//        pulse width values are a width in microseconds >= 1.0).  If a pulse
//        width/duty cycle is not given, the default is 50% duty cycle.
//        Note that most devices have limits of the output frequency and
//        width/duty cycle that is available, and may be different for each
//        output... consult your device manual.
//
//        For the SRO100 PA sets the PPS tracking alarm window.
//
//
//      For the Symmetricom X72 and SA22 rubidium oscillators you can set
//      the ACMOS output frequency:
//         PN  - set the ACMOS output frequency or divider ratio.
//               If you follow the input number with an 'H' the frequency
//               will be set to the closest possible value in Hz (accuracy
//               is limited by the interger divider ratio)
//
//
//
//   TRAIM CONTROL
//
//      Many GPS timing receivers support a feature called TRAIM - Time
//      Receiver Autonomous Integrity Monitoring.  TRAIM mode monitors the
//      timings from the various satellites and, ifinconsistencies are
//      detected, can drop suspect satellites from the timing solution, set
//      alarm conditions, etc.  Consult your device manual.
//
//        PT   - configure device TRAIM mode / threshold.
//               For TAPR TICC devices this sets the "FIXED TIME2" values.
//               For the SRO100 PT sets the PPS tracking window half-width.
//
//
//
//
//
//-NON-VOLATILE CONFIGURATION EEPROM/FLASH/SRAM memory
//
//   Some receivers support saving all or parts of the receiver configuration
//   into some form of nonvolatile memory (like EEPROM).  Configuration
//   saves are currently supported on Trimble, Ublox, and Venus/Navspark devices.
//   Also the HP-5071A cesium beam oscillator.  The Symmetricom X72 and SA22
//   rubidium oscillators also support EEPROM, but what gets saved is not
//   documented and may vary depending upon the firmware version.  The
//   TruePosition GPSDO has an undocumented "$UPDATE FLASH" command the EE
//   sends.
//
//   Whenever EEPROM is written Heather sounds a BEEP.
//   If you hear lots of unexpected beeps,  something cold be
//   wrong and you may be wearing out the EEPROM.  Note that SCPI
//   type devices also sound a BEEP when a receiver message response does
//   not seem to match what was expected (loss of message sync).
//
//   Jupiter receivers automatically write things like almanac data to EEPROM
//   and will periodically produce EEPROM write BEEPs.  After a power-on there
//   will be quite a few during the first hour or so.
//
//      /kc     - toggles disabling of writing configuration data into EEPROM
//      /kc1    - disable writing into EEPROM
//      /kc0    - enable writing into EEPROM
//
//
//      EE      - from the keyboard, writes the complete current receiver
//                configuration to EEPROM/BBRAM/FLASH.  
//
//                For Venus receivers this command toggles the enable of 
//                writing configuration changes to flash memory.  If writing 
//                to flash is enabled, the receiver status column will 
//                show "FLASH: WRT" instead of "FLASH: OK".  Once "write flash"
//                mode is enabled any new configuration changes are saved to
//                flash.  Previous changes are not written to flash.  Writing
//                to flashdefaults to OFF for Venus receivers amd changes 
//                are only saved to battery backed RAM (if available).
//
//                For the PRS-10 rubidium oscillator this command will prompt
//                you to select the parameter that should be saved.  The
//                default prompt is for the last paramter that you changed.
//                Entering "ALL" will save the current values of all the 
//                save-able paramters.
//
//                Changing any of the PPS/OSC/Cable delay parameters
//                from the keyboard stores the values in EEPROM unless EEPROM
//                writes have been disabled.  Changing them from the command
//                line does not cause an EEPROM write.
//
//
//
//
//
//-ADEV (and MTIE) CALCULATIONS and DISPLAYS
//
//   Lady Heather can calculate and display various ADEV (Allan Variance/
//   Deviation) values from the receiver readings.  ADEVs are a way of 
//   characterizing how stable a signal is over various time intervals.
//   Heather supports simultaneous ADEV, MDEV, HDEV, and TDEV calculation.  
//
//   If the main "receiver" type is a time interval counter (like the TAPR
//   TICC) Heather can also calculate and display MTIE (Maximum Time 
//   Interval Error).  In this section, MTIE can be considered to be just
//   another xDEV type,  but xDEVs and MTIE cannot be shown on the screen
//   at the same time.
//
//   The AI command enables the MTIE display.  Heather uses Bregni's algorithm
//   to calculate MTIE.  Bregni's algorithm is very fast but limits the
//   intervals to powers of 2.  The maximum time interval used is the largest
//   power of 2 <= the adev queue size value.  MTIE CALCULATION STOPS
//   WHENEVER THE MAXIMUM TIME INTERVAL IS REACHED.  The CI command will 
//   clear the MTIE data and start over.
//
//
//   --------------------------  WARNING --------------------------
//
//   Unless you are using a time interval counter (like the TAPR TICC)
//   the ADEV values are based upon the PPS and OSCillator
//   error values reported by the unit.  These values (aka bogo-adevs) are 
//   not derived from measurements made against an independent reference
//   (other than the GPS signal) and may not agree with ADEVs calculated
//   by measurements against an external reference signal (true adevs). 
//
//   Bogo-adevs tend to diverge more from true adevs at shorter taus (say 
//   less than 30 seconds) and somewhat less at longer taus.  Values at 
//   the middle of the tau range can be quite close to true adevs.
//
//   ADEVs calculated when the oscillator is undisciplined are more 
//   meaningful than when the oscillator is being disciplined.  For proper 
//   true ADEV values, you should use a proper external Time Interval Counter.
//
//   Not all devices report values that are even suitable for ADEV 
//   calculations... Mostly the Trimble GPSDO devices are usable.
//
//   If the ADEV values were calculated from receiver data, the ADEV
//   type in the table headers is shown in lower case.  ADEVs derived from
//   time interval counters are shown in upper case.
//
//   If the ADEVQ: queue size message on the screen is shown in GREY, that
//   means that the receiver potentially has data that ADEVs can be calulated
//   on, but that data is not time-related and that ADEV calculations are
//   blocked.  You can un-block them by explcitly setting the adev queue
//   size with the /a= command line option.
// 
//   ---------------------------------------------------------------
//
//
//   SELECTING THE ADEV/MTIE TYPE TO DISPLAY
//
//   Heather maintains a separate circular data buffer of the values that
//   it uses to calculates ADEVs from.  The queue contains a PPS related
//   value and an OSCillator related value.  The size of the ADEV queue
//   determines the maximum "tau" time interval that the ADEVs can show.
//   The default is 33,000 points which is suitable for values of TAU out
//   to around 10,000 seconds.  
//
//   You can set the size of the ADEV (and MTIE) queue from the command line:
//      /a=size - sets the number of points to save in the ADEV queue.
//                A size of 0 will disable ADEV calculations.  Every 10000
//                ADEV queue entries uses around 1.0 megabytes of memory.
//                If MTIE data is being used (with a time interval counter)
//                this increases to around 7.5 megabytes.
//
//   Normally Heather shows the xDEV queue size on the screen in WHITE.  If
//   the device does not support xDEVs and the xDEV queue memory has not
//   been allocated it will be shown in GREY.
//
//
//   Normally Heather collects a new ADEV entry every second.  You can adjust
//   the ADEV interval with:
//      /j=secs  - sets all ADEV queue sample intervals 
//      /ja=secs - sets chA (PPS) ADEV queue sample interval
//      /jb=secs - sets chB (OSC) ADEV queue sample interval
//      /jc=secs - sets chc ADEV queue sample interval
//      /jd=secs - sets chd ADEV queue sample interval
//      /jo=secs - sets chB (OSC) ADEV queue sample interval
//      /jp=secs - sets chA (PPS) ADEV queue sample interval
//
//
//   You can clear the ADEV queue from the keyboard:
//      CA - clear the ADEV and MTIE queues
//      CB - clear the ADEV and plot queue
//      CI - clear the MTIE data queue
//
//   You can clear the ADEV or MTIE queue and reload it from the porttion
//   of the plot queue currently being shown on the screen:
//      CR - reload the ADEV queue from the plot queue data being shown.
//   When using the TAPR TICC (or other) time interval counter this
//   command also reloads the MTIE data from the plot queue TIE points 
//   displayed. Note that the CR command can produce errors if the device
//   is actively sending data to Heather.
//
//   The CR command lets you examine the ADEVs and MTIE data of a selected
//   portion of the captured data.  Set the plot view interval to the length
//   of the data segement you want to analyze (V command).  Use the plot
//   scrolling commands to move the first point of the data to be analyzed
//   to the left edge of the plot area then issue the CR command.  Note that
//   unless plot updates are disabled (U command) new incomming data will be
//   added to the ADEV and MTIE data queues.
//
//
//
//   Heather can also read ADEV information from files using the "R"
//   keyboard command.  ADEV files must have an extension of .ADV  
//   These files can have three independent values per line.  The first value
//   if the "PPS/chA" value, the second one is the "OSC/chB" value, the third
//   value is the TAPR TICC channel C value (and is mostly useless)  These
//   values don't have to be actual PPS and OSC values, but that is how
//   Heather refers to them in the menus.
//
//   The .ADV files can also can contain:
//      # text comments
//      #title: title text (note that the ': ' is required)
//      #period seconds_between_readings (default=1)
//      #scale  pps_scale_factor  osc_scale_factor  
//
//   The first line of an ADV file must be a '#' line.
//
//   The scale factor value multiplied by the data values should yield 
//   nanoseconds.
//
//   Note that the #period command erases any data values that appeared 
//   before it in the file.
//
//   Reading an ADEV file pauses the processing of data from the receiver.
//   THe "U" keyboard command can resume receiver updates.
//
//
//   Heather can also read a time interval error (TIE) value file for 
//   calculating MTIE.  TIE files must have an extension of .TIE   
//   A TIE file consists of lines of up to  4 channels of TIE 
//   data (chA chB chC and chD) per line.  Comment lines start with a '#'.
//
//
//
//   ADEV INFORMATION DISPLAY
//
//   Heather displays ADEV info in two ways.  First is a table of ADEV values.
//   Second is as graphs in the plot area.  If a time interval counter (like
//   the TAPR TICC) Heather can also display MTIE values.  (MTIE is Maximum 
//   Time Interval Error, a common measurement used in the telecom industry).
//
//      GA  - from the keyboard toggles the ADEV plots on and off
//      /ga - from the command line
//
//   If the ADEV plot is enabled, then the division markers in the plot area
//   that represent decades are highlighted in CYAN.  Each highlighted
//   vertical division represents a power of 10.  Each minor division marker
//   is a linear division of that decade.  The decade value of the top line of 
//   the plot area is determined from the largest ADEV value seen in any
//   of the ADEV tables.  All ADEV types are scaled the same.  When ADEV plots
//   are being displayed the TAU values are labeled at the top of the plot
//   and the decade values are labeled at the right side.
//
//   Each highlighted horizontal division represents TAU with divisions of
//   powers of 10 seconds (TAU 1,10,100,1000,10000,,..)  The horizontal major
//   divisions between the highlighted ones are a 1:2:5 division of 
//   that time decade (like 1,2,5,10,20,50,100...).
//
//   Heather's ADEV plots differ from conventional ADEV plots.  Conventional
//   ADEV plots are drawn with a log-log scale.  Heather's plots use a linear
//   scale (this is necessary because Heather's data plots share the same plot
//   grid).  The vertical scale is logarithmic by decade, but linear within 
//   the decade.
//
//   For screen resolutions 800x600 and below,  the ADEV plot decades 
//   are scaled to single VERT_MAJOR divisions (not to every two major 
//   divisions)
//
//
//   The ADEV table is always shown on the screen if there is space for it
//   (in the upper right corner of the screen).  The "GB" keyboard command
//   allows for one of the satellite maps or the watch display to be shown 
//   in the plot area.
//
//   If more than one of the map displays and/or watch display is enabled
//   they take precedence over the ADEV table display.
//
//   Clicking on the adev table display will switch the screen to the
//   "all adevs" mode.  The screen will be configured to display all four
//   adev types of the adev table that you clicked on.
//   Cicking again will restore the screen to its previous state.
//   Note that short clicks might be ignored... particularly on devices
//   like UCCM receivers that only output time updates every two seconds.
//   It can help to hold down the mouse button until the screen changes.
//
//
//   If the adev tables have more adev bins calculated than will fit on
//   the screen,  you can scroll through them.  See the PLOT WINDOW section
//   above for information on scrolling through the ADEV tables.
//
//
//   Heather always calculates all four ADEV types for both the PPS and OSC
//   values (and the TAPR TICC in TIMELAB mode, the channel C data).  
//   The "A" keyboard menu is used to configure the ADEV information to 
//   display:
//      AA - Show ADEVs for the OSC and PPS values
//      AH - Show HDEVs for the OSC and PPS values 
//      AI - Show MTIEs for the TICC chA and chB values (the MTIE display is
//           only available if using a frequency/time interval counter)
//      AM - Show MDEVs for the OSC and PPS values 
//      AT - Show TDEVs for the OSC and PPS values 
//      AP - Show all ADEV types for the PPS / channel A value
//      AO - Show all ADEV types for the OSC / channel B value
//      AC - Show all ADEV types for the TAPR TICC channel C value
//      AD - Show all ADEV types for the TAPR TICC channel D value
//
//   You can also select the ADEV type(S) from the command line:
//      /oa - Show ADEVs for the OSC and PPS values
//      /oh - Show HDEVs for the OSC and PPS values 
//      /oi - Show MTIEs for the TICC chA and chB values 
//      /om - Show MDEVs for the OSC and PPS values 
//      /ot - Show TDEVs for the OSC and PPS values 
//      /oo - Show all ADEV types for the OSC value
//      /op - Show all ADEV types for the PPS value
//      /oc - Show all ADEV types for the TAPR TICC channel C data (currently useless)
//      /od - Show all ADEV types for the TAPR TICC channel D data (currently useless)
//
//      The "all adev" commands (AP / AO / AC / AD) let you
//      control what info to plot.  All four ADEV plots
//      only, all four ADEV types and the graphs (can be a
//      bit confusing since the same colors are used for
//      two different things),  or the two regular (PPS/OSC or CHA/CHB)
//      ADEV plots and graphs:
//         AOA - show all four OSC ADEVs tables and all ADEV plots
//         APA - show all four PPS ADEVs tables and all ADEV plots 
//         ACA - show all four channel C ADEVs tables and all ADEV plots 
//         ADA - show all four channel D ADEVs tables and all ADEV plots 
//
//         AOG - show all four OSC ADEVs tables and all plots
//         APG - show all four PPS ADEVs tables and all plots
//         ACG - show all four channel C ADEVs tables and all plots
//         ADG - show all four channel D ADEVs tables and all plots
//
//         AOR - show all four OSC ADEVs tables and regular ADEV plots
//         APR - show all four PPS ADEVs tables and regular ADEV plots 
//         ACR - show all four channel C ADEVs tables and regular ADEV plots 
//         ADR - show all four channel D ADEVs tables and regular ADEV plots 
//
//
//      Sometimes the scaling of one (usually TDEV) or more of the xDEV/MTIE
//      plots will interfere with the display of the plots of the other 
//      types.  You can selectively turn off (or on) the plots of one 
//      or more of the data types with the AX keyboard command or the /ax
//      command line option:
//         AXA  - toggle display of ADEV plots
//         AXH  - toggle display of HDEV plots
//         AXM  - toggle display of MDEV plots
//         AXT  - toggle display of TDEV plots
//         AXP  - toggle display of PPS/chA xDEV/MTIE plots
//         AXO  - toggle display of OSC/chB xDEV/MTIE plots
//         AXC  - toggle display of chC xDEV/MTIE plots
//         AXD  - toggle display of chD xDEV/MTIE plots
//
//         /axa - toggle display of ADEV plots
//         /axh - toggle display of HDEV plots
//         /axm - toggle display of MDEV plots
//         /axt - toggle display of TDEV plots
//         /axp - toggle display of PPS/chA xDEV/MTIE plots
//         /axo - toggle display of OSC/chB xDEV/MTIE plots
//         /axc - toggle display of chC xDEV/MTIE plots
//         /axd - toggle display of chD xDEV/MTIE plots
//         /ax  - enable display of plots all xDEV/MTIE types
//
//
//      Heather defaults to scaling the ADEV bins into a 1-2-5 sequence.
//      The AS keyboard command or /as= command line option let you modify
//      the bin scaling sequence.  
//         /as=0  all adevs (next tau = tau + 1)
//         /as=1  one bin per decade
//         /as=2  one bin per octave
//         /as=3  3dB per decade (displayed tau is rounded to an integer)
//         /as=4  1-2-4 decades
//         /as=5  1-2-5 decades
//         /as=8  1-2-4-8 decades
//         /as=10 10 bins per decade
//         /as=29 29 (linearly spaced) per decade
//         /as=99 logarithmic linearly spaced bins
//
//      Heather is limited to calculating a maximum of 100 bins.  The number
//      of ADEV bins that can be plotted or shown on the screen is limited
//      by the amount of screen space available.  The full adev info is 
//      written to the log file whenever it is closed or Heather exits.
//      You can scroll through the adev tables and plots as mentioned above.
//
//      Note that changing the bin scaling sequence causes Heather to
//      recalculate the adevs from the adev queue data.  If the adev queue
//      had overflowed the new adev calculations and numbers will not use 
//      data that had been accumulated before the queue had overflowed.
//
//      Recalulating the adev values (either due to manually changing the 
//      bin scaling sequence or automatically due to an adev queue overflow)
//      can take a long time on slower machines.  For instance recalculating
//      all 4 adev types on 36,000 adev queue entries on a Raspberry PI3
//      can take around 25 seconds).  When recalculating the adevs, the
//      keyboard will not respond.
//
//
//      The AE keyboard command or /ae= command line option toggles the 
//      display of ADEV error bars in the plots.  Error bars that are shown
//      with arrow points on the ends indicate an adev bin with not enough
//      data to produce a meaningful error estimate.  Error bars smaller than
//      one minor plot division are not shown.
//
//
//
//
//-USING HEATHER WITH FREQUENCY AND TIME INTERVAL COUNTERS
//
//   Heather can be used with frequency and time interval counters in two
//   different ways:
//
//     1) As the primary "receiver" device
//     2) As an auxiliary (extra) input device.  When used as an auxiliary
//        device the counter readings are used to calculate true ADEV values
//        (instead of the "bogo-adevs" calculated from the receiver
//         self-reported disciplining loop parameters).
//
//    To use a counter as the primary "receiver" device use:
//       /rxi - input device is a counter
//       /rx1 - input device is an HP-531xx counter.
//              /rxi will usually work with the HP counters, but /rx1 can be
//              used to force the issue.
//
//    Heather does a pretty good job for determining the counter type from
//    the data that it see, but you can also use the following commands to 
//    force the counter type when /rx1 or /rxi has been specified:
//       /itc - force generic counter mode
//       /ith - force HP counter mode
//       /itl - force Lars GPSDO controller counter mode
//       /itp - force PICPET counter mode
//       /itt - force TAPR TICC counter mode
//
//    To use a counter as an auxiliary input device, see the section on
//    the /ei command command.
//
//    If the primary input device is a counter, the /ei command allows you
//    to connect a second counter to add more channels of data (two TAPR
//    TICCs allows four channels of data to be analyzed).
//
//
//    When using Heather with a counter as the primary input device, Heather
//    enters ADEV mode and displays ADEV/HDEV/MDEV/TDEV and/or MTIE of the
//    input signals.  It has most of the functionality of the popular
//    TIMELAB progam, but none of the cool slickness... but it does run under
//    Linux, macOS, and FreeBSD.  See the section of ADEVs for info on
//    configuring and controlling the ADEV displays.  TAPR TICC data is best
//    displayed on screens with a width of 1280 pixels.
//
//
//    For generic counters, Heather does not send commands to the counter or
//    change the counter configuration.  With the TAPR TICC there are several
//    commands that can configure the device.  Consult the TAPR TICC manual for
//    more info on these settings.
//       PM - set the data type mode
//       PE - set the input signal edge to use
//       PE - set the channel "fudge" factor settings
//       PT - set the channel "TIME2" factor settings
//       PS - set the channel "time dilation" settings
//       PS - set the device sync mode
//       PC - set the device calibration period
//       PR - set the device ref clock
//       PK - set the device coarse clock
//       &a - auto-tune TIME2 and fudge factor values
//
//    The user must configure the main and secondary counters with the same
//    settings and operating mode.  To configure the second TICC
//    start Heather with the second device's port specified as the 
//    main input device, configure it, shut down Heather, then
//    restart Heather with the first TICC specified as the main
//    device and the second TICC as the extra device.
//
//
//
//    Heather needs to know what kind of data the counter is providing. 
//    All counter channels must be using the same data type.
//       /imi - time interval data
//       /imf - frequency data
//       /imp - period data
//       /imt - timestamp data
//       /imd - TAPR TICC debug data
//       /iml - TAPR TICC Timelab data
//
//       PM from the keyboard also sets the counter data type.
//
//    Note that the TAPR TICC supplies data type information, but these
//    commands let you override the TICC info, but this will probably cause
//    errors.
//
//
//    Heather converts and proceees all counter readings into time intervals.
//    The data is displayed as Time Interval Errors (TIE data).  TIE is the
//    difference from the reading to the nominal frequency of the oscillator
//    being analyzed.
//
//    You should configure frequency counters with a 1 second gate time.
//    For the TAPR TICC, etc  use a divider to drive the counter with a
//    1 PPS input signal.
//
//
//    Heather needs to know the nominal frequency of the data source being
//    analyzed.  The nominal frequency of all channels defaults to 10 MHz.
//    Setting the nominal frequency also sets the phase unwrap interval used
//    when processing frequency data.
//    You can specify the nominal frequency of any channel like:
//       /if=5E6  - set all channels to a 5 MHz nominal frequency
//       /ifa=15E6  - set channel A to 15 MHz nominal frequency
//       /ifb=10E6  - set channel B to 10 MHz nominal frequency
//       /ifc=1E6   - set channel C to 1 MHz nominal frequency
//       /ifd=10000000  - set channel D to 10 MHz nominal frequency
//       /ifo=15E6  - set channel A to 15 MHz nominal frequency
//       /ifp=10E6  - set channel B to 10 MHz nominal frequency
//       
//      PN from the keyboard also sets channel nominal frequencies.
//      The PN command is not available when using Symmetricom Rb
//      oscillators.
//
//
//  Heather can also display the TIE data as frequency error data:
//      GP# - Display channel A data as frequency errors
//      GO# - Display channel B data as frequency errors
//      G7# - Display channel C data as frequency errors
//      G8# - Display channel D data as frequency errors
//
//
//  Heather can also display phase data of the input signals:
//      G1  - Display channel A phase data
//      G2  - Display channel B phase data
//      G3  - Display channel C phase data
//      G4  - Display channel D phase data
//      GV  - Display phase data for all channels
//
//  Instead of raw phase data, Heather can display phase data residuals of 
//  the input signals.  Phase resiuals are the least squares inear trend line 
//  of the phase data subtracted from the phase data.
//      G1=  - Display channel A phase residuals
//      G2=  - Display channel B phase residuals
//      G3=  - Display channel C phase residuals
//      G4=  - Display channel D phase residuals
//
//
//  When operating on frequency data, Heather needs to "unwrap" phase data.
//  To do this, it needs to know what phase wrap interval to use.  Heather
//  normally bases this upon the nominal frequency setting using the formula:
//  (1.0 / nominal_frequency)... the actual value used to unwrap phase data is
//  half that value.  You can override this setting using:
//      /pwa=seconds   - for channel A data
//      /pwb=seconds   - for channel B data
//      /pwc=seconds   - for channel C data
//      /pwd=seconds   - for channel D data
//      /pwp=seconds   - for channel A data
//      /pwp=seconds   - for channel B data
//      /pw=seconds    - for all channels
//      PW             - from the keyboard.  You can specify up to 4 phase
//                       wrap intervals for CHA, CHB, CHC, and CHD separated
//                       by spaces.  The PW command is not available when using
//                       SRO100 rubidium oscillators or STAR4 GPSDOs.
//
//      Values of 0 seconds says to disable phase un-wrapping.
//      Negative values say to use the nominal frequency to set the phase
//      wrap interval.
//
//
//    Timestamping mode counters have a limited range that the timestamps
//    cover.  After this amount of time, the timetamps "wrap".  Heather
//    normally reduces all timestamps modulo 100 seconds.  This value is 
//    good for most applications.  You can force the timestamp wrap interval
//    to any value.  All channels use the same timestamp wrap setting:
//       /twi=seconds
//       PI  - from the keyboard
//
//    The PICPET timestamp counter chip has a rather coarse resolution (100 ns
//    with a 10 MHz clock).  This can produce rather noisy plots.  Try setting
//    a long-ish display filter with the FD keyboard command... like FD 60)
//   
//    The Lars GPSDO is a simple GPSDO controller that can work with any
//    GPS device that outputs a 1PPS signal.  It disciplines an external
//    10 MHz oscillator.  You can use the Lars GPSDO either as a TIC (in 
//    period mode) as the main input device or you can use it as an "extra"
//    input device. In "extra" mode you use the GPS receiver as the main input
//    device and the Lars GPSDO data as the "extra" input device.  The Lars
//    GPSDO reports the PPS error deviation from 1Hz (i.e. time interval
//    error), the GPSDO DAC setiing, and the GPSDO temperature.  If the 
//    receiver does not report one of these values, the Lars GPSDO data is
//    shown.  If the GPS receiver sends one of those values, the GPS receiver
//    data is shown.  The Lars DAC setting is labeled "DACL",  the Lars
//    temperature value is labeled "TEMPL", and the PPS value is labeled "PPSL".
//    Note that the xDEVs from the Lars GPSDO are calculated from the GPSDO
//    control loop values and are not referenced to an external reference.
//    They are what Heather refers to as "bogo adevs".
//
//
//
//
//-MISCELLANEOUS RECEIVER CONTROL COMMANDS
//
//
//   RESTARTING and RESETTING the RECEIVER
//
//      !W  - warm start the receiver
//      !C  - cold start the receiver
//      !H  - hard reset the receiver to factory defaults
//
//            Note that on many receivers doing warm/cold/factory resets may
//            take a long time and Heather may take a long time to 
//            re-establish communications or Heather may not be able to 
//            re-establish communications, or may change the receiver language
//            type.  You may need to exit and restart Heather.
//
//
//
//   SERIAL PORT CONTROL
//      !S  - re-initializes the serial port connection and receiver data
//            parser
//
//      !Z  - reset the receiver message data parser
//
//      !P  - set operating system serial port parameters (like the /br
//            command line option)  Note this changes the operating system
//            serial port configuration and NOT the receiver serial port  
//            parameters.
//
//            In order to guard against accidentally "bricking" a receiver 
//            by setting a hard-to-recover-from configuration,  Heather 
//            does not ever change the receiver serial port configuration. 
//            (someday this command might be able to configure the receiver 
//             serial port parameters)
//
//      !B  - send a 300-500 msec BREAK to the serial port
//
//
//
//   EDITING FILES
//       N  - pressing N on the keyboard brings up WORDPAD (NANO on
//            Linux and macOS_ to edit/view a file.  The default file
//            is heather.cfg
//
//
//   SENDING COMMANDS to RECEIVER
//      !U  - sends a command string to the receiver.  This is mainly for
//            NMEA, SCPI, and other  receivers that accept ASCII commands.  
//            For NMEA receivers you do not need to include the leading '$' 
//            character.  Also the NMEA checksum will be automatically 
//            added if it is not included (no '*' in the command).
//
//            On the Lucent RFTG-m GPSDO this command disables the unit and
//            causes the other unit to assume control.  Use !R to re-enable
//            the unit.
//
//
//   RUNNING RECEIVER DIAGNOSTICS
//      !D  - command the receiver to run its internal self-tests.  Note that
//            on many devices this takes a long time and/or resets the receiver 
//            and Heather may take a long time (or forever) to re-establish 
//            communications.
//
//
//   SWITCHING RECEIVER MESSAGE FORMATS
//      !M  - If a receiver can speak NMEA, but is currently running in its
//            native binary mode,  this will switch the receiver back to NMEA.
//            On receivers that are speaking Motorola binary data, this command 
//            usually switches the receiver from Motorola mode to some other
//            (device dependent) language.
//
//
//   CHANGING THE RECEIVER NAVIGATION / MESSAGE OUTPUT RATE
//      /nr=Hz - from the command line
//      !R=Hz  - many modern receivers can output data at greater than 1 Hz.
//               This command lets you change the "navigation rate" of the
//               receiver.
//
//               Note that most timing receivers cannot provide an accurate
//               1 PPS signal unless they are running at 1 Hz navigation rate.
//
//               High navigation rates produce a lot of data and serial port
//               traffic.  If the receiver serial port is set to a low speed,
//               they usually drop messages to lower the data rate. Some
//               receivers just go bonkers.  This condition usually shows up
//               as lots of time-skip indications in the plot area and/or
//               jittery watch or digital clock displays.
//
//               Sometimes a high navigation rate produces enough serial port
//               traffic that Heather never sees an idle time in the data 
//               stream where it can process keyboard commands.  The keyboard
//               will stop responding.  You can recover from this by killing
//               the program and restarting it with the /nr=1 command line
//               option to lower the navigation rate back to 1 Hz.
//
//               Also with high navigation rates and plot auto-show mode (the
//               VT keyboard command) you might not be able to exit the
//               program from the keyboard (particularly with a lot of data
//               in the plot queue).  You can exit the program by clicking on
//               the exit button in the title bar or turning off VT mode (try
//               V0) before exiting.
//
//
//
//   TERMINAL EMULATOR
//
//      Heather has a built in terminal emulator program that is handy
//      for monitoring data from the receiver and sending ASCII commands to it.
//      Receiver data is shown in GREEN and user keystrokes are shown in
//      YELLOW.
//
//         !T  - enter terminal emulator from the keyboard
//         /bt - start Heather in terminal emulator mode from the command line
//
//      If you use /rxx (no receiver type, use system clock) along with /bt
//      Heather will work as a simple terminal emulator.  The program will
//      exit when you press the END key.
//
//      You can also use the /rxte (or /rxtt) command line option to operate
//      heather as a terminal emulator program.  You can set the port
//      configuration with /rxte=...   where ... is the device desciptor
//      string as documented for the external device commands ("/ei" command).
//
//      Normally the terminal emulator sends keystrokes immediately when a
//      key is pressed.  Use /rxtb for a stand-alone terminal emulator with
//      a buffered keyboard that only sends keystrokes when CR is pressed.
//      This is needed for the OSA-453x devices with firmware that times
//      out after 175 msecs betweem keystrokes (who was the bastard that
//      thought that was a good idea?)
//
//      The terminal emulator mode has several keyboard commands for
//      controlling it:
//        
//         END    - exit terminal emulator
//         HOME   - erase the screen
//         UP     - re-sends the last keyboard line to the receiver
//         F1     - toggle keystroke echo mode
//         F2     - toggle writing receiver data to a receiver data capture
//                  capture file.  Heather uses the "raw data capture log" 
//                  file name. If the data capture file is open, it is closed.
//                  If it not open, it is opened in "append, binary" mode.
//         F3     - toggle HEX binary data display mode.  In HEX mode
//                  bytes that could be part of a start/end-of-message 
//                  sequence are shown in YELLOW
//         F4     - toggle writing to the screen
//         F5     - CR-LF mode - adds a CR after any LF or add an LF after
//                  any CR (this option does not show up the terminal emulator
//                  help info header!)
//         F8     - send a BREAK
//     
//
//     The !O keyboard command brings up a serial port data monitor screen.
//     This shows all data sent to or from a given serial port.  Pressing any
//     key will exit the monitor mode.
//
//     The ZO command also brings up a data monitor screen for the main
//     input device. Received message data bytes are shown in GREEN and 
//     sent messagee bytes are shown in YELLOW.
//
//
//
//   RPN CALCULATOR
//
//      Heather has a built-in RPN calculator mode.  RPN calculators are
//      based upon a postfix stack based architecture as popularized by
//      the Hewlett Packard scientific calculators.  Heather's calculator
//      defaults to a six level stack.  The first entry on the stack is
//      usually called "X" and the next entry is "Y".  Heather also implements
//      100 memory registers (0 .. 99).
//
//      Calculator mode is entered with the "`" (backwards quote) key.  
//      Multiple values and operations can be entered on a line.
//      To exit calculator mode enter a blank line or ESC when the calculator
//      prompt is being shown  or enter a '`' (backward quote) or ESC when the
//      calculator prompt is not being shown.
//
//      The calculator is also available in a full screen zoomed mode via
//      the Z` keyboard command.  
//
//      Heather can also be run in "calculator only" mode by starting it
//      with the /rxca command line option.  The only way to exit
//      "calculator only" mode is with the EXIT calculator command or by
//      clicking on the exit icon in the program title bar.
//
//      The current stack values are shown in the plot area.  The "X" value
//      is at the bottom of the list).  After exiting calculator mode
//      the GR keyboard command (redraw screen) will erase the stack
//      display from the plot area.  
//
//      Operations marked with an '*' work with angles. The input and output
//      values will be in either degrees or radians (depending upon the 
//      current RAD or DEG setting).
//
//      Numbers can be in entered in either fixed point (3.1459) or exponent
//      (12.34e-5) format.  Hexadecimal integers can be entered like 0xABCD.
//      Binary integers can be entered like 0b1101.  Octal integers can be
//      entered like 0o123.   Note that binary/octal/hex numbers cannot be
//      signed.  Use the CHS command to make them negative.
//
//      As an example a calculator command line:
//         45 sin 2 * sqr
//      Will results in a X value of 2.0000:  calculates sin(45), multiples
//      the value (0.707...) by 2, then squares the result.
//
//
//      Basic math operations:
//         +    - add X and Y
//         -    - subtract X from Y
//         *    - multiply X and Y
//         /    - divide Y by X
//         inv  - 1.0 / X
//         mod  - fmod(Y,X)    
//         max  - maximum value of X and Y
//         min  - minimum value of X and Y
//         chs  - change sign of X
//         abs  - absolute value of X
//         int  - integer part of X
//         frac - fractional part of X
//         nop  - no operation
//
//         ctof - centigrade to farenheit
//         ftoc - farenheit to centegrade
//         ftom - feet to meters
//         mtof - meters to feet
//         rn   - resistor noise in nV/sqrt(Hz)  (input Y=degrees C   X=ohms)
//
//      Logical operations (on 64 bit integers, but note that the numbers
//      are processed via double precision values so only the lower 54 bits
//      may be valid due to the double precision exponent bits).
//         ~    - complment X
//         &    - AND X and Y
//         |    - OR X and Y
//         ^    - XOR X and Y
//         >>#  - shift X right #places (1 place if # not given)
//         <<#  - shift X left #places (1 place if # not given)
//
//      Trig functions:
//         deg   - treat/display values as degrees
//         rad   - treat/display values as radians
//         rtod  - radians to degrees (X * 180.0 / PI)
//         dtor  - degrees to degrees (X * PI / 180.0)
//         sin   * sine(x)
//         cos   * cosine(x)
//         tan   * tangent(x)
//         asin  * arcsine(x)
//         acos  * arccosine(x)
//         atan  * arctangent(x)
//         atan2 * atan2(Y,X)
//         rtop  * rectangular to polar (theta->Y, r->X)
//         ptor  * polar to rectangular (Y input is theta, X is R)
//         dms   * break up angle in X to degrees minutes seconds
//         dec   * convert degrees minutes seconds (Z Y X) to decimal
//         dist  - linear distance between two points (X Y and Z R)
//         diag  - diagonal distance - sqrt(X*X + Y*Y);
//         gcd   * great circle distance and azimuth between two locations
//                 (X=LON1 Y=LAT1 [destination])   (Z=LON2 R=LAT2 [source])
//         bearing * azimuth between two locations (X=LON1 Y=LAT1 [destination])
//                   (Z=LON2 R=LAT2 [source])
//
//      Powers and logarithms:
//         sqrt  - square root X
//         sqr   - X*X
//         ln    - ln(X)
//         log   - log base 10 (X)
//         exp   - e^X
//         powe  - e^X
//         pow10 - 10.0^X
//         pow   - Y^X
//         **    - Y^X
//
//   Time and date maniipulation:             
//         date      - put display date (yyyy mm dd onto stack Z Y X)
//         time      - put display time (hh mm ss onto stack Z Y X)
//         greg      - convert X (JD value) to gregorian onto the stack)
//         local     - local time as a Julian date
//         utc       - UTC time as a Julian date
//         gps       - GPS time as a Julian date
//         mjd       - UTC time as a Modified Julian Date
//         gtime     - time since GPS epoch (in days)
//         utime     - time since Unix epoch (in days)
//         tzjd      - time zone offset as a Julian time (fraction of a day)
//         tz        - time zone offset in hours
//         leap      - current leapsecond count (UTC offset)
//         week      - gps week
//         tow       - gps time of week
//         epoch     - gps epoch as a julian date
//         secs      - convert hours minutes seconds (Z Y X) to seconds
//         dow       - convert hours min secs (Z Y X) to day of week (0..6)
//         ti        - stopwatch timer value (TI keyboard command value)
//
//         rise      - sun/moon rise time as a Julian date (local time)
//         noon      - sun/moon noon/moon transit as a Julian date (local time)
//         set       - sun/moon set time as a Julian date (local time)
//                       The rise/noon/set times will be for either the sun
//                       or moon... depending upon how the main screen is
//                       configured (with the TR M keyboard command).
//
//      Display formatting: # is the number of decimal point digits. If #
//      is not given, use the current setting.  Note that there is no space
//      before the #.
//         fix#   - fixed point notation (unless value is too large)
//         sci#   - scientific notation (mantissa and exponent)
//         exp#   - engineering notation (exponents are a multiple of 3)
//         hex#   - ASCII hex format (integer only!)
//         oct#   - ASCII octal format (integer only!)
//         bin#   - ASCII octal format (integer only!)
//         comma# - toggle formatting the integer part with "comma" every 4
//                  digits.  # is the option "comma" character.  If # is 
//                  a '.' then also replace the decimal point with 
//                  a ',' (european style mumbers)
//         zoom   - switch to zoomed calculator screen mode
//
//      Stack manipulation:
//         ex    - exchange X and Y value
//         ent   - push X onto stack
//         enter - push X onto stack
//         clx   - clear X value
//         clear - clear stack and memory registers
//         cls   - clear stack
//         clm   - clear memory registers
//
//         roll   - rotate the stack down 1 position
//         roll#  - rotate the stack down # positions
//         down   - rotate the stack down 1 position  (same as roll command)
//         down#  - rotate the stack down # positions (same as roll command)
//         up     - rotate the stack up 1 position
//         up#    - rotate the stack up # positions
//         drop#  - remove # entries from the stack
//         stack# - push stack entry# onto the stack
//         swap#  - swap X with stack entry# 
//
//      Memory operations:  # is the register to use (0..99).  If # is not
//      given, register 0 is used.
//         rcl#  - push reg # onto the stack
//         rcl+# - add reg # to X
//         rcl-# - subtract reg # from X
//         rcl*# - multiple X by reg #
//         rcl/# - divide X by reg #
//         rcl@# - push reg[reg[#]] onto the stack (indirect recall)
//
//         sto#  - store X in reg #
//         sto+# - add X to reg #
//         sto-# - subtract X from reg #
//         sto*# - multiply reg # by X
//         sto/# - divide reg # by X
//         sto@# - store X in reg[reg[#]]  (indirect store)
//  
//      Constants and values:  These commands push the indicated value onto
//      the stack.
//         last      - the previous X value
//         lastx     - the previous X value
//         pi        - 3.14159...
//         \         - 3.14159...
//         e         - 2.81828...
//         c         - speed of light in meters per second
//         h         - Plank's constant (6.62607015E-34)
//         k         - Boltzmann's constant (1.380649E-23)
//         t0        - Absolute zero (-273.15)
//         spd       - seconds per day (24*24*60)
//         spw       - seconds per week (24*24*60*7)
//                
//         lat       * current latitude
//         lon       * current longitude
//         alt       * current altitude
//         lla       * current lat, lon, alt
//
//         dac       - current DAC/Sawtooth setting
//         temp      - current temperature setting
//         pps       - current PPS plot value
//         osc       - current OSC plot value
//                
//         cable     - current cable delay value in ns
//         elmask    * current elevation mask filter setting
//         amu       - current signal level filter setting
//                
//         dop       - average DOP value
//         pdop      - current PDOP
//         hdop      - HDOP
//         vdop      - HDOP
//         gdop      - GDOP
//         tdop      - TDOP
//         edop      - EDOP
//         xdop      - XDOP
//         ydop      - YDOP
//         tfom      - time figure of merit
//         ffom      - frequency figure of merit
//                
//         tc        - GPSDO time constant
//         damp      - GPSDO damping factor
//         gain      - GPSDO oscillator gain in Hz/Volt
//         initv     - GPSDO initial voltage
//
//                
//   For these values, # indicates the desired satellite.  Note that there 
//   is no space before the #. If # is not given then the highest elevation 
//   satellite is used.  #=1000 is the SUN, #1001 is the MOON
//         az#       * azimuth of satellite PRN #
//         el#       * elevation of satellite PRN #
//         sig#      - signal level of satellite PRN #
//         doppler#  - doppler of satellite PRN #
//         range#    - pseudorange of satellite PRN #
//         phase#    - code or carrier phase of satellite PRN #
//         prn#      - place all sat measurements on the stack
//
//
//   Conditionals operations: If the comparison is true the next operation on
//   the line is processed and the second operation is ignored.  If the 
//   comparison is false the next operation is ignored and the second 
//   operation is processed.  This is similar to the "compare ? true : false" 
//   operation in the C language.
//         x=y
//         x<>y
//         x<y
//         x>y
//         x>=y
//         x<=y
//
//         x=#   - (# is a numeric constant, 0 if not given)
//         x<>#
//         x<#
//         x>#
//         x>=#
//         x<=#
//
//         dsz   - decrement x and skip next instruntion if 0
//         isz   - increment x and skip next instruntion if 0
//
//         nop   - no operation
//         break - skip the rest of the line
//         again - loop back to the start of the line
//
//   User defined operations:
//      You can create user defined opeations using the DEFINE command:
//          define name op1 op2 ... opn
//
//      Once a command is DEFINEd you can invoke it by name just like any 
//      built in command.  DEFINE names must start with a letter.  You
//      can DEFINE up to 100 new commands.
//
//      You can re-DEFINE built-in operations that start with a letter (but
//      this is not generally a good idea).
//
//      You can also edit user defined operations:
//          edit name
//      or you can simply re-DEFINE an existing DEFINE.  If you don't specify
//      any string after the define name, the DEFINE is deleted.
//
//      User defined operations can use other user defined operations.  The
//      maximum execution nesting level is 10.
//
//      You can save all your DEFINEd operations with the "savedefs" command.
//      The file extension should be .rpn if you want to re-load it using
//      the "R" keyboard command.  Or the calculator "run" command can also
//      be used ("run" accepts any file name extension).
//         savedefs filename.rpn
//
//      You can save all DEFINEs and the current memory and stack using
//      the "saveall filename" command.
//
//      At startup, Heather can read calculator commands from the file
//      "heather.rpn"  The entries in the file should start in column 1.
//      The file can contain any calculator commands, but is mainly
//      intended to load user DEFINEd calculator commands.
//
//      You can read in calculator RPN files using the "R" keyboard
//      command (file extension must be .rpn) or with the calculator
//      "run" command.  Lines that begin with a blank or tab are
//      ignored.  This feature lets you use the .RPN files to implement
//      more complex functions than will fit on a single line.
//
//      The "again" operation should only be used after a conditional
//      comparison that you KNOW can be reached.  Otherwise the calculator
//      will loop forever!   You can break out of a "hung" AGAIN loop by
//      pressing any key.
//
//
//
//   EXECUTING AN EXTERNAL PROGRAM     
//      !E  - This command prompts for a command line for the operating
//            system to execute.  It spwans a shell to run the specified
//            program,  For this command to work under Linux/macOS/FreeBSD
//            the "xterm" program must be installed (it is part of most
//            Linux distros, but it is not part of the standard Raspberry Pi 
//            distro, but can be installed).
//            
//            
//
//
//-ON SCREEN KEYBOARD and TOUCH SCREEN SUPPORT
//
//   Heather now supports an on-screen "touch screen" keyboard.  It is
//   accessed by touching or clicking the mouse in the upper left-hand corner
//   of the screen.  The touch screen must emulate a mouse for it to work.
//   Enabling of the on-screen keyboard may be toggled with the /kv 
//   command line option.
//
//   The on-screen keyboard has a "CAP" key... this actually does a
//   shift-lock function, not a caps-lock function. The key label changes
//   lower case to upper case when caps-lock is on.
//
//   The on-screen keyboard also has a "MOU" key.  When on (key is labeled
//   in upper case) then whenever the mouse is in the plot area the left
//   mouse button is treated as being the right mouse button.  This
//   allows the plot scrolling function to be used with a touch screen.
//
//   If the file "heather_click.wav" exists in the heather installation
//   directory, it is played whenever an on-screen keyboard key is pressed
//   or the screen is clicked to zoom an item to full screen.
//
//   Note that for several small Raspberry PI SPI interfaced
//   touchscreens the touchscreen driver does not work
//   well (or at all).  It ignores touches!.  You can
//   improve this by using the /mb command line option.
//   This maps the SCROLL WHEEL and RIGHT buttons to be
//   the same as the LEFT button.  The touch response will
//   be rather slow... you have to hold the touch for 2-3
//   seconds before it will be recognized... sucks, but 
//   such is life...
//
//
//
// SCREEN CLICK HOTSPOTS
//
//   In addition to the standard mouse clicks in the plot area actions,  
//   clicking the mouse (or pressing a touch screen) can cause various other
//   actions.  These special "hot spots" are:
//
//   Upper left 100x100 pixels on the main screen (the time/date information) 
//   brings up the touchscreen keyboard if it has been enabled (/kv command)
//
//   Upper left 100x100 pixels on a "zoomed" screen - exits the zooomed screen
//
//   The "receiver data" area at the top of the screen next to the time/date
//   info block - does an immediate screen image capture just like you pressed
//   the "\" key.   This also works on zoomed screen displays, even though
//   the "receiver data" is not being shown.
//
//   The LAT/LON/ALT table on the main screen - zooms the lat/lon/alt
//   scattergram to full screen.
//
//   The satellite info table - zooms the screen to the full satellite info
//   table,  satellite position map,  and satellite signal level map.  If the
//   satellite info table is not on the screen, clicking to the left of the
//   first digit of the digital clock will also do this.
//
//   The area under the satellite info table - zooms the digital clock to
//   full screen.
//
//   The digital clock - zooms the screen to the digital clock display.
//
//   The analog watch or satellite maps - zooms the clicked item to full
//   screen.
//
//   The plot area header text - zooms the plot to full screen.  If the plot
//   is zoomed to full screen,  clicking on the upper right 100x100 pixel of
//   the screen will simulate pressing the "DEL" key to get out of 
//   "plot review" mode.
//
//   If the keyboard "Z" command has been used to enable a zoomed screen
//   display,  clicking on various items in the zoomed display will zoom that
//   item to full screen.  Clicking on items on a zoomed display that was
//   created by clicking on a main screen item will NOT zoom that item... it
//   will return to the main display screen.
//
//
//
//
//-MISCELLANEOUS COMMANDS
//
//   There are several commands that don't fall under any of the previous
//   sections.
//
//
//   Heather uses a color palette of 16 colors: 0..15   With 0=black and 
//   15=bright white.  You can modify entries in the color palette map:
//      /cm=color,r,g,b    where color is the color number (0..15) to
//                         change and r,g, and b are the RED GREEN and 
//                         BLUE values (0..255).
//   
//   
//
//
//   Whenever Heather is idle and not doing something or receiving data
//   from the GPS receiver, it does a short Sleep() that returns control
//   to the operating system and greatly reduces the CPU usage.  You can
//   specify how long to Sleep() for in milliseconds:
//      /tw[=#] - Sleep() for # milliseconds when idle (default=10)
//
//
//
//   You can control the audio functions of Lady Heather:
//      /kb     - toggle Beeps from the command line
//      /ks     - toggle playing Sound files from the command line
//      /rb     - toggle showing (in the plot title) reason code for beeps
//
//      GS      - toggle all sounds from the keyboard.  If beeps OR sound
//                files are enabled, they will both be disabled.  If beeps
//                AND sound files were disabled, they will both be enabled 
//                and a BEEP will be sounded as confirmation.
//
//
//   Normally you exit Heather from the keyboard by pressing "ESC y".  You
//   can allow ESC ESC to exit the program with:
//      /ke     - toggle quick exit with ESC key
//
//
//   You can put Heather into a "read-only" mode that blocks sending commands
//   to the receiver over the serial port.  This mode can interfere with
//   functions or displays that require commands to be sent to the receiver:
//      /ir     - toggle read-only mode for receiver commands
//
//
//   This is similar to the "/ir" command, except it blocks sending ALL data
//   out the serial port:
//      /is     - toggle read-only mode for serial port
//
//
//   Normally Heather periodically polls the receiver for various pieces of
//   data,  status,  or configuration information.  Usually a new piece of
//   information is polled for every second.  It can take around 30 seconds
//   for Heather to acquire everything from the receiver.  You can block
//   Heather from polling the receiver for data.  This is mainly useful when
//   using the "TK" command to analyze receiver message timing.
//      /ix     - toggle no-polling mode for receiver data
//
//
//   Heather can output some debug information (mainly on Linux and macOS).
//   This debug information is independent of the debug log file and most
//   goes to stdout. This command line option sets the level of debug 
//   information that is shown.
//      /de[=#] - set debug information level
//
//
//
//   The "R" keyboard command can read some other type of files. Many of these
//   file formats are also readable from the command line using the "/r="
//   command line option.
//
//      You can read lat/lon/alt logs.  These files
//      must have an extension of ".LLA"   Data lines require:
//        time-of-week  flag  lat  lon  alt
//        flag=0 means good reading,  otherwise skip it
//      This format can be generated by TBOLTMON log command.
//      Other .LLA file commands supported are:
//         # text comments
//         #title: Title text (note that the ': ' is required)
//         #lla: ref_lat  ref_lon  ref_alt (your assumed exact location)
//      The first line of an LLA file must be a '#' line.
//
//      You can play/test sound files.  These files must have an file name
//      extension of ".WAV"
//
//      You can read greetings calendar files.  These files must have an file
//      name extension of ".CAL"
//
//      Can also read ".TIM" files from John Miles' TI.EXE
//      program.  The .TIM file CAP/TIM/IMO, PER, and SCA commands are
//      used.
//
//      If you attempt to read a file that does not have a filename .EXTension
//      or end in a '.', Heather tries to read a .ADV, .CAL, .CFG, .GPX,
//      .KML, .LLA, .RAW, .SCR, .SIG, .TIM, .TIE, .WAV, and .XML files 
//      in that order.
//
//
//   The "N" keyboard command brings up a text editor  The default editor 
//   used is NOTEPAD in Windows, NANO on Linux and macOS, and EE on FreeBSD.
//   You can specify an editor to use by setting the "HEATHER_EDITOR" or
//   "EDITOR" environment variables.  You can view/edit any file... the 
//   default is "heather.cfg"  To use this command on Linux/macOS/FreeBSD 
//   the "xterm" program must be installed (it is not part of the standard 
//   Raspberry Pi distro, but can be installed).
//
//   The /ne command line option disables the file editing and execution
//   commands.  Once /ne is used, it cannot be re-enabled.  This command is
//   a security measure to block possible malicious exploitation of these
//   features.  On Linux/macOS "/ne /ne" also disables playing of sound files
//   vis system() calls to APLAY.
//      
//
//
//   A few legacy command line options... nothing to see here, move
//   along...
//
//      /lo     - enable reading of old format LUXOR log files
//      /lh     - don't write timestamp headers in the log file when the file
//                is periodically synced to the disk.
//
//   In WINDOWS, both the TCP/IP link and help dialog features use
//   a windows message timer to keep the program running
//   if the command line help dialog box is active or the screen is
//   being dragged, etc.  At one time, this timer had the potential to
//   cause very intermittent, random "unhandled exception"
//   aborts, but this seems to have been fixed.  You can still disable the 
//   timer feature with the:
//      /kt     - toggle Windows dialog/message timer
//
//
//   The "/bs" command line option will adjust the displayed time by the
//   solar Equation of Time.  The only indication that solar time is in use 
//   is on the analog watch display. The watch name/day of week will 
//   be "Solar".  Using solar time is now best done with the "TZ" and "/tz"
//   time zone commands.
//
//
//   /nt  - attempt to wake up Nortel "telecom" GPSDOs  (this is now
//          done automatically)
//
//
//
//   You can change the input device on the fly
//   from the keyboard with the /# or /ip keyboard command
//   just like from the command line.
//   Changing the input device from the keyboard resets
//   the satellite tracking and signal level maps.
//   You can also use these commands to re-establish communications
//   to a dropped connection or device.  If you had
//   previously set an IP connection address/port, you
//   don't have to type the "=addr:portnum" after the /ip
// 
//   You can also use the "/rx" commands from the keyboard to change
//   the input device type.  Note that Heather attempts to configure itself
//   for the new input device, but sometimes not all the settings and data
//   will be updated for the new device.  Changing the device on the fly
//   may not always work properly.
//
//
//
//   Added '$' and '=' command line/.CFG file  options for 
//   building lists of hex bytes to send to the receiver
//   The '=' list is sent when the program starts.  The '$'
//   list is sent when a primary timing message is received
//   (i.e. once each second).  For example with a TSIP receiver:
//       $10,3a,00,10,03   would request doppler/code phase 
//                         data every second. 
//       $10,3C,00,10,03   would request satellite status
//                         and position data every second. 
//   Note that the '$' and '=' command line options should 
//   not be preceeded by a '/' or '-'.
//
//
//
//
//  Revision History (from version 5.0):
//
//    6.14 - Modified "n" keyboard command to allow editing of arbitrary files.
//           Under Windows it spawns the "notepad" editor.
//           Under Linux and macOS it spawns the "nano" editor.
//           You can also specify an editor to use with the "EDITOR" or
//           "HEATHER_EDITOR" environment variables.
//
//           Added PAGE_UP editing character to retreive the last line entered
//           so you can recover from a botched edit or easily repeat the last
//           command value.
//
//           Changed default plot statistic to show to SPAN (was RMS).  SPAN
//           is the difference between the maximum and minimum values shown
//           in the plot area.  Be aware that not all plotted values may
//           be available immediately after Heather has started collecting
//           data.  Those values will be assumed to be 0 and this can affect
//           the SPAN value.  It can help to clear the plot queue (CC or CP
//           keyboard command once Heather has valid data from all the
//           plotted variables.
//
//           If the user specifies the Trimble TSIP receiver type with the
//           /rx? command line option the base file name for output files was 
//           changed from "tbolt" to "starloc","acutime", "sv6", or "res_t".
//           If the receiver type was autodetected (or is a Thunderbolt) 
//           the base file name is "tbolt".
//
//           If the user specifies the Lucent SCPI receiver type with the /rxf
//           command line option the base file name for output files was 
//           changed from "scpi" to "lucent". If the receiver type was 
//           autodetected the base file name is "scpi".
//
//           If the user specifies the Nortel SCPI receiver type with the /rxy
//           command line option the base file name for output files was 
//           changed from "scpi" to "nortel".  If the receiver type was 
//           autodetected the base file name is "scpi".
//
//           Fixed "n" keyboard command to not break other two letter keyboard
//           commands that end in "n".
//
//           Added the Gp/? command to show a snapshot of all 7 plot
//           statistics for plot "p".
//
//           Fixed an issue where some SCPI receivers were not displaying
//           latitudes in the southern hemisphere properly.
//
//           Modified code to allocat ADEV or MTIE data queues only if
//           these features are being used.
//
//           Modified /gb command to toggle shared_plot... previous versions
//           always enabled shared_plot.   Also if /gb is issued from the
//           keyboard the screen is re initialized in order for the new 
//           setting to take effect.
//
//           Modified satellite info table to allow sat PRN numbers up to 999.
//           This is because some receivers don't use the industry standard
//           PRN numbers for Galileo and Beidou, etc GNSS satellite systems.
//           THIS MODIFICATION CHANGES THE SUN and MOON PRN NUMBERS USED IN
//           LOG FILES FROM 256/257 to 1000/1001!
//
//           Added support for the Motorola @@Bg and @@Eg raw observation
//           data messages (used for the VPZ carrier phase capable Oncore
//           receivers.
//
//           Fixed issues with early model Motorola receivers displaying the
//           signal level.  These Motorola receivers report the signal level
//           as a value between 0 and 255.  Heather likes signal levels in 
//           the 0 .. 50ish range, so the sat and signal level maps were not 
//           properly displayed.  Heather now convets the sig level using 
//           20*log10(sig)... the resulting value agrees quite well with 
//           what later model Mototola receivers report in dBc.  This formula
//           is also now used with SCPI receivers that report "SS" signal
//           levels in the 0..255 range (like the Z3801A).
//
//           Fixed some potential issues with displaying the command line
//           help info on Linux/macOS/FreeBSD machines.  Allowed mouse/
//           touchscreen click to skip to the next page of help info.
//
//           Allowed screen heights/widths down to 320 pixels.  Sizes less than
//           640x400 require use of scaled vector fonts (/vq or $Q commands).
//
//           Added the EXPERIMENTAL /vq and $Q commands to draw characters 
//           using a scaled vector font instead of the normal dot matrix font.
//           The font size can be scaled from 50 to 500 percent.  Scaled
//           vector fonts can help the readability of text on large screens 
//           or to increase the plot area size on small screens.
//
//           Added EXPERIMENTAL /vd and $D commands to use a 480x320 screen
//           size (this use 75% scaled vector fonts).  Expect some srceen
//           formatting issues and you may need to change some display item
//           selections (watch, clock, shared mode, etc) particularly if you
//           change the screen res from the keyboard.
//
//           Added EXPERIMENTAL /ve and $E commands to use a 320x480 screen
//           size (this use 60% scaled vector fonts).  Expect some srceen
//           formatting issues and you may need to change some display item
//           selections (watch, clock, shared mode, etc) particularly if you
//           change the screen res from the keyboard.
//
//           Added EPERIMENTAL /vo and $O commands for rotating the image
//           in the screen window.  This can be useful when used with something
//           like using a 480x320 LCD as a 320x480 vertical format display.
//
//           Added the /pt= command line option to set the program title
//           bar text.  You can also set the title bar text from the keyboard
//           with the GG command.  Use &b as the first two characters of 
//           the title.  If the title bar string is empty, Heather uses the
//           receiver type as the title.
//
//           Added "!e" keyboard command to execute an external program.
//           You enter the command line to start the program and it will run
//           in another window.
//
//           If an invalid two character keyboard command is entered you
//           get a beep and the srceen flashes an error message.
//
//           Reworked processing of simulation input files.  You no longer
//           need a receiver to be connected to process a simulation file.
//
//           Added /sw= command line option to control pacing of message 
//           processing when reading a simulation file.  The value specifies
//           how long to delay in milliseconds after each message is read.
//           
//           Fixed a spacing issue in the "/rx" command line help dialog.
//
//           Added the ability to sound the alarm at a specifed time on
//           the day that a calendar file greeting is triggered.
//
//           Allowed up to 5 greetings to match and be displayed on any
//           day.
//
//           Fixed HP5xxxx/Z3816/Z3817 receiver (/rx5) initialization control
//           message that turns off receiver full duplex mode.  Heather now
//           turns off full-duplex mode for all SCPI receivers.
//
//           Added support for a touch screen keyboard.  Clicking on the
//           UPPER LFFT corner of the screen brings up a touch screen keyboard.
//           The keyboard is automatically hidden whenever a keyboard command
//           is completed or one of the blank "keys" is clicked.  The "/kv"
//           command line option toggles enabling of the touch screen feature.
//
//           Added support for the numeric keypad on Linux/macOS/FreeBSD.
//
//           Added support for "heather_click.wav" sound file that plays
//           whenever a touch screen key or item is touched.  It is also
//           played every second in "tick clock" audible clock mode.
//
//           Added TH #T keyboard command and /th=#t command line options for 
//           enabling the audible "tick clock" that ticks each second and
//           beeps each minute.  The sounds can be changed by supplying
//           the files "heather_second.wav" and "heather_minute.wav"
//
//           Added the /tl command line option for showing dates in the ISO
//           yyyy.mm.dd format
//
//           Fixed an issue on X11 systems where the mouse was responding
//           to clicks on a window sitting on top of the Heather window.
//
//           Fixed an issue on Windows systems to force the screen width
//           to even values when setting a custom screen size. WIN_VFX
//           barfs if screen width is an odd number.
//
//           Improved screen formatting for NO_RCVR mode on small screens
//           and screens with large width:height ratios.
//
//           Modified screen formatting for custom screen sizes so no wasted
//           blank space appears below the plot area.
//
//           Added -vp and $P commands for enabling a 800x480 screen display
//           (like the official Raspberry PI touchscreen display)
//           For X11 based systems "-vp" also enables full screen mode.
//
//           Added /vp and $P (800x480 - Raspberry PI) screen size command (*)
//           Added /vr and $R (1024x600) - Reduced screen size command (*)
//           Added /vj and $J (1280x800) screen resolution. (*)
//           Added /vk and $K (1280x960) screen resolution.
//           The screen types marked (*) can open in full screen mode on
//           Linux type systems... they are standard touchscreen sizes for
//           devices like the Raspberry PI.
//
//           Added full screen display mode for (X11 Linux / macOS displays)
//           using the -fu command line option. This must be used in 
//           combination with an explicit screen size command that EXACTLY
//           matches the monitor size... e.g.  "/vc=800x480 /fu" or
//           "/vm /fu".  If the specified screen size does not match the 
//           monitor size, all sorts of not-good things can happen. XQuartz
//           for macOS has problems with full screen mode.
//           
//
//           Improved SCPI receiver recovery from commands that reset
//           the receiver.  It no longer does an auto_detect() which messed
//           up Lucent devices because of their different com port parity 
//           than the Z3801A.  Also resets the SCPI command queue.
//
//           Improved the auto-detect of SCPI receivers.  Lucent KS devices
//           are now auto-detected.  The auto-detect routine now uses
//           19200:8:O:1 and if the device appears to be a SCPI device with
//           ODD parity, the setting is automatcially changed to 19200:7:O:1.
//           Also improved the overall reliabilty of the auto-detect routine.
//
//           Added support for the F1..F9 function keys to read keyboard
//           script files "f1.scr" to "f9.scr".  This allows F1..F9
//           (also F10 on X11 systems) to be used as programmable function
//           keys.
//
//           Clicking on the UPPER RIGHT corner of the zoomed plot display
//           exits plot review mode without exiting zoomed plot mode.
//
//           Tweaked some screen size display arrangement thresholds to allow
//           better displays on X11 systems where a few pixels are lost to
//           the window borders.
//
//           Added code so X11 systems to keep the screen updating while
//           scrolling the plot using the righthand mouse button.  
//           Modified the signal level maps to use "fresher" data.  Previous
//           versions kept averages of every reading seen at a given az/el
//           position since the program started.  Now the averages are reset
//           to their current value once a day.  This makes it easier to
//           spot changes in the antenna system performance... they won't be
//           masked by potentailly weeks of old data.
//
//           Modifed clicking on an adev table to show all four adev values
//           for the selected adev table type.  Previous versions only
//           supported clicking on the upper adev table and the adev tables
//           for the value selected by the "AO" or "AP" keyboard command was
//           used.
//
//           Added support for touch screen control of plot markers and
//           skipping to the next error event.  Heather remembers the last
//           column that the mouse cursor was in the plot area at.  This is
//           shown by a small GREEN dot at the top of the plot area. If the
//           mouse cursor is outside of the plot area (like in the touch
//           screen keyboard) the plot marker control keyboard commands 
//           (0..9, @, =, +, -) use this position.
//
//           Heather now remembers the last plot scrolling/positioning keyboard
//           command ([, ], {, }, <. >, +, -)  This command can be replayed
//           by clicking/touching in the "Receiver data" area near the top left
//           corner of the screen.  This is useful on touch screens so you
//           can scroll or move the plots without having to bring up the
//           touch keyboard for each desired movement. For instance, you want
//           to fine tune the plot position a few pixels to the left.  Press
//           the '[' key.  This moves the plot one pixel to the left.  Now
//           click in the "Receiver data" area.  Each click show shift the
//           plot left another pixel
//
//           Added support for FreeBSD (note: FreeBSD has no standard
//           sound system so sound effects are not available (unless you can
//           implment the "aplay" program and modify the play_tune() function).
//
//           Modified automatic leap second screen capture to work with
//           devices that report the leap second as a duplicated xx:59:59 or
//           xx:00:00.  Also the status column now shows that the leap second
//           screen was captured.  Fixed screen capture for receivers that
//           have a negative value for the /tsx receiver message time offset
//           (like SCPI receivers).
//
//           Modifed the "/br=" command line option to allow "," separators.
//           Also, if a field is not given, that value is not changed. Previous
//           versions set the missing value to a default value.
//
//           Reworked the com port data loss timeout code to only use extended
//           timeout intervals while processing commands (like diagnostics and
//           device resets) that take a long time.
//
//           Added /ct= command line option to allow setting all the com port
//           data loss timeouts (in msecs >= 3000). Normally Heather uses a
//           5000 msec com timeout.
//
//           Added /ct?= command line option to allow setting a specfic port
//           data loss timeout (in msecs >= 3000). Normally Heather uses a
//           5000 msec com timeout.  Replace the '?' character with the port
//           identifier character.
//
//           Added /ce command line option to toggle com port data / port
//           loss recovery.  If com data is lost or the com port disappears
//           Heather will attempt to re-init the com port every "com_timeout"
//           interval.  This new feature defaults to ON.
//
//           Modified scheduled events (screen dump, log dump, alarm, exit)
//           to not require an exact time match to trigger.  They now trigger
//           on the next time message at or after the specified time.  This
//           allows them to work if the receiver has a time skip at the
//           specified time.
//
//           Added TQ and /tsk commands for showing the digital clock in
//           Modified Julian date.time format.
//
//           Added TI and /tsw commands for showing the elapsed time interval
//           (stopwatch time) on the digital clock.
//
//           Added /tph command line option for showing temperature as
//           degrees Paris Hilton.
//
//           Added the SR keyboard command for changing the lat/lon/alt
//           scattergram reference point.
//
//           Modified the plot display filter commands so that a negative
//           value selects a "per-pixel" filter count based upon the plot
//           view interval and plot width.  Negative values for the filter 
//           count no longer invert the temperature plot like previous
//           versions did.
//
//           Added the /va command line option to start up in "VT" View-Auto
//           scale plot view mode.
//
//           Modifed the display filter code to average the points each side
//           of the queue entry.  Previous versions averaged the points
//           after the queue entry. The new method keeps the "phase" of the
//           averaged display point aligned with the unaveraged queue data.
//
//           Added the ability to display the derivative of a plot's data.
//           For instance GPD will change the PPS plot to the derivative of
//           the plot.  In derivative mode, the ':' after the  plot statistic
//           label in the plot header is replaced by an '*'.
//
//           Added support for allowing multiple serial and TCP/IP ports to
//           be open at the same time.  This allows for future support of
//           things like external time interval counters and other devices
//           and echoing receiver data to an external device.
//
//           Added receiver data "echo" ports.  These ports echo the data from
//           the receiver to an external device.  The /ee[=device] command
//           echos the receiver data in its' native format.  The /ek]=device]
//           command echos the receiver data in NMEA format.
//
//           Added support for environmental temperature/humidity/pressure
//           sensors (/en command).  Currently only the dogtatian.com
//           and lookingforsolutions.com USB sensorr are supported.
//
//           Added /et command to send the moon, sun, and sat position(s) out a
//           port.  This data can be used to implement an antenna / solar 
//           tracker.
//
//           Added support for using a dedicated serial port for the 
//           temperature control device.  The /ef= command enables the
//           external temperature control port.
//
//           Modifed the way that "missing" odd numbered seconds are simulated
//           on receivers that only send time every other second.  The 
//           simulated seconds are now generated "on-time". Before, they were
//           generated immediately after the even numbered seconds time
//           message.  This also works for simulating missing seconds that
//           occur while polled receivers (like SCPI and Star-4 devices) are
//           processing long commands like the SYST:STAT command.
//
//           Added support for ancient Trimble SV6/SV8 receivers (/rx6 command
//           line option)
//
//           Added support for ancient Trimble ACE-III receivers (/rxai
//           command line option... these are currently treated as a SV6/SV8)
//
//           Added support for ancient Trimble Palisade receivers (/rxpr
//           command line option) - not yet fully tested
//
//           Added support for Trimble Acutime (/rxag, /rxan, and /rxat
//           command line options) - not yet fully tested. /rxan is ACUTIME 360,
//           multi-gnss systems.  /rxag is Acutime GG, /rxat is for older 
//           models like the Acutime Gold and Acutime 1000/2000.
//
//           Added support for ancient Trimble TAIP receivers (/rxp command
//           line option)
//
//           Added support for Datum TymServe 2000 receivers (/rxts command
//           line option)
//           
//           Added support for the Lars simple GPSDO controller time interval
//           data.  The Lars device can either be used as the main input device
//           (as a time interval counter device) or as an "extra" time interval
//           counter device.
//
//           Added support for ancient Lucent RFTG-m GPSDOs (/rxf command
//           line option)
//
//           Added support for Novatel SuperStar II (/rxss command
//           line option) - currently untested
//
//           Added support for the SRS PRS-10 rubidium oscillator (/rxpr
//           command line option)
//
//           Added support for the Spectratime SRO100 rubidium oscillator
//           (/rxsr command line option)
//
//           Added support for Spectrum TM4 GPSDOs (/rxtm command line
//           option)  - Note I don't have one to test the command that set
//           options and values!
//
//           Added support for the Symmetricom rubidium oscillators.  These
//           cannot be auto-detected, but Heather does try to determine the
//           model from the devide responses. Use /rxsy for auto detect model,
//           /rxx7 to force X72,  /rxx9 to force X99,  /rxsa to force SA22).
//           /rxsb allows use with telecom versions that have a 58.9824 master
//           oscillator instead of the normal 60 MHz ones.
//
//           Added support for the Temex/Spectratime LPFRS and RMO rubidium
//           oscillators (/rxlp command line option)
//
//           Added support for TruePosition GPSDOs (/rxo command line
//           option)
//
//           Added support for Venus/Navspark RTK receivers.
//           Added !k keyboard command for setting Venus RTK base/rover mode 
//           and RTCM output.
//
//           Added support for Zyfer Nanosync 380m GPSDOs (/rx3 command
//           line option)
//
//           Added support for the TAPR TICC (and some other) time interval
//           counters for dong ADEV analysis. The /rxi command line option 
//           specifies time interval analyzer mode. Also /rx1 can be used
//           for other generic counters if /rxi does not properly identify
//           the attached device.  Note that /rx1 defaults to 9600 baud
//           and /rxi defaults to 115,200 baud.
//
//           Added support for Tom Van Baak's PICPET simple timestamping
//           time interval counter chips for dong ADEV analysis. The /rxpp
//           command line option specifies time interval analyzer mode.
//           The PICPET sends data at 19200,8,N,1 unless driven by a
//           non-10MHz clock.  Heather works with 2.5, 5, 10, and 20 MHz clocks
//           or 15 MHz on Windows systems (because most Linux systems don't
//           support the resulting 28800 baud serial data).  With a 10 MHz
//           clock the PICPET resolution is 100 nsec.  This can produce
//           rather noisy plots.  It is best to set a long-ish display filter
//           time (FD command - try FD 60).
//
//           Added support for a terminal emulator only mode (/rxte or /rxtt)
//           command line option).  This works like the /bt command line option
//           but when you exit terminal emulator mode, Heather exits.  Also
//           you can specify the device / parameters like /rxte=... where
//           "..." is the device settings info as documented for external
//           device command line options (like /ei).
//
//           Added /np and TP commands for running a keyboard script at
//           a specified time or interval.
//
//           Added /nc and TC commands for running an external program
//           at a specified time or interval.  The program to run is 
//           deterined by the "HEATHER_EXEC" environment variable.  If it has
//           not been set, then the default program "heather_exec" is run.
//
//           Added /ne command line option to disable the file editing and
//           execution commands.
//
//           Added /bm and !o commands for enabling a port data monitoring
//           screen.  Data from the port is shown in GREEN. Data sent to the 
//           port is shown in YELLOW.  The monitor screen can be in either 
//           hex or ascii.  You can specify the port to monitor.
//           To exit port monitoring mode press any key.
//
//           Added ZO command to monitor receiver port traffic and show it as
//           a zoomed screen display.
//
//           Added ZH command to monitor receiver port traffic and show it as
//           a formatted hex/ascii zoomed screen display.
//
//           Modified ZN command to display a blank screen.  On previous versions
//           ZN would cancel the current zoomed screen display.  This is now
//           done with the ZZ command.
//
//           Added ZT command to set a keyboard inactivity timeout (in
//           minutes).  After the specified time has passed without any
//           keyboard activity, the screen switches to the specified zoomed
//           screen display.
//
//           Added ZQ command for zoomed full screen calendar display.  (ZQ
//           used to be the same as ZS zoomed signal display).
//
//           Added TB keyboard command to show calendar for a specifed year.
//
//           Added /zs? to start up with zoomed display '?'
//
//           Modifed !t and /bt commands to allow connecting the termnial
//           emulator to any port.
//
//           Modified NMEA handler to prioritize the message used to generate
//           the time code and update the screen:  GxZDA, GxRMC, GxGGA, GxGNS
//           The GGA and GNS messages do not have a date in them.  If the date
//           has not been seen in a NMEA message, the system clock date is
//           used.  Once a higher priority message has been seen, the lower
//           priority ones are not used for time keeping.
//
//           If adev values are being plotted, the plot area is labeled with
//           the taus at the top of the plots and the decades at the right
//           side of the plots.  The adev labels are show in GREEN.  Turning 
//           off the adev plots removes the adev labels.
//
//           Modifed default ADEV queue size to 43200 points (12 hours).  It
//           was 36000 points.
//
//           Added /ja (or /jp),  /jb (or /jo), /jc, and /jd command line
//           options for individually setting the ADEV queue period.
//           /j sets all queue periods to the same value.
//
//
//           Added /im? command for forcing the time interval counter data
//           type to ?  (default for /im is Timestamp mode).  If the mode is
//           not forced for non TAPR TICC counters, the mode is set to
//           'I' (time interval). Other counter modes include:
//              F - frequency
//              I - interval 
//              P - period   
//              T - timestamp
//              D - debug (TAPR TICC)
//              L - Timelab (TAPR TICC)
//
//
//           For TAPR TICC devices the "P" menu is used to configure the
//           device.  Any changes to the device configuration take around
//           5 seconds to process and will reset the plot and adev queues.
//           Selecting the "P" menu will also change the display mode to
//           show the current device configuration.  While the device
//           configuration is being shown any keypress will restore the
//           screen to normal operation.
//
//           For TAPR TICC devices the PC command sets the device calibration
//           periods value.
//
//           For TAPR TICC devices the PD command sets the "Time Dilation"
//           values.
//
//           For TAPR TICC devices the PK command sets the device coarse
//           clock interbal (in microseconds).
//
//           For TAPR TICC devices the PM command sets the device operting
//           mode.
//
//           For TAPR TICC devices the PE command sets the input edge 
//           polarity for the channels.
//
//           For TAPR TICC devices the PF command sest the channel delay 
//          "FUDGE" values.
//
//           For TAPR TICC devices the PR command sets the device reference
//           clock frequency (in MHz).
//
//           For TAPR TICC devices the PS command sets the sync mode
//           value.  WRANING: don't enable slave mode unless a slave device
//           is connected.  To recover from a missing slave device, start
//           Heather with terminal emulator mode enabled (/bt) and used the
//           TICC menu to set the sync mode to master.
//
//           For TAPR TICC devices the PO command sets the device timeout
//           value.
//
//           For TAPR TICC devices the PT command sets the "FIXED TIME2"
//           values
//
//           For TAPR TICC devices the &a command starts an "autotune"
//           proceedure that sets the FUDGE and TIME2 parameters.  For
//           autotune to work you must have a 1PPS signal connected to the
//           TICC inputs via cables with matched lengths (use a "T" adaper
//           with matched cable between the "T" outputs and the TICC inputs).
//           You specify the number of seconds to analyze.  It must be 
//           greater than 30 seconds, but values over 1800 seconds are 
//           recommened.
//
//           For TAPR TICC devices, selecting the '&' keyboard menu will
//           show the TICC parameters... type "& ESC".  This will show
//           the paramter settings and stop showing the ADEV tables.  Press
//           any key to resume the normal display.  On wide screen monitors
//           (at least 1280 pixels wide) the TICC config info is part of the
//           normal display.
//
//
//           Added /twi= command line option for setting the time interval
//           (in seconds) that timestamps wrap at.  The default setting is to
//           reduce all timestamp values modulo 100.0 seconds.
//
//           Added PW keyboard and /pw# command line options for setting the
//           time interval counter phase wrap time (default = 100.0E-9 for a
//           10.0 MHz oscillator)
//
//
//           For Symmetricom X72 compatible devices the &a command calculates
//           the DDS tuning value that will set the 10 MHz output to the
//           correct frequency.
//
//           Added a software disciplining algorithm for the X72 and SA22
//           rubidium oscillators that do not have firmware that supports
//           discipling with a 1PPS input.
//
//
//           Added support for displaying MTIE (Maximum Time Interval Error)
//           of TICC / interval counter data.  The AI command enables the
//           MTIE display.  The maximum time interval used is the largest
//           power of 2 <= the adev queue size value.  MTIE calculation
//           stops whenever the maximum time interval is reached.  The CI
//           command will clear the MTIE data and start over.
//
//           The WM command writes the current MTIE data to a file. The MTIE
//           results are also written when a log file is closed.
//
//
//           Added /dq=filename command line option and WT keyboard commands
//           for writing TICC data to a file when both a receiver and and
//           a TICC are in use at the same time.  Receiver data goes to the
//           /dr (or WY) receiver data capture file and TICC data goes to the
//           /dq (or WT) TICC data capture file.
//
//           Added /as= command line option for setting the ADEV bin spacing.
//           also AS keyboard command, Heather is limited to 100 adev bins.
//               /as=0  all tau (not practical)
//               /as=1  one bin per decade
//               /as=2  one bin per octave
//               /as=3  3dB per decade
//               /as=4  1-2-4 decade
//               /as=5  1-2-5 decade
//               /as=10 10 per decade
//               /as=29 29 (linearly spaced) per decade
//               /as=99 log spaced
//
//           Added /ae command line option and AE keyboard option for toggling
//           the display of ADEV error bars in the plots.
//
//           Added the '~' keyboard option to patch a point in the plot queue
//           that has a data glitch.  Position the mouse cursor on the
//           offending point and press '~'.  This will replace the point's
//           data with the previous data point.  You may want to then use
//           CR command to recalulate xDEV and MTIE values from the patched
//           queue data.
//
//           Added the Gp~ command to automatically remove all glitches from
//           a selected plot (where p is the plot to de-glitch).
//
//           Added calculation of solid earth tide displacements (in mm) and
//           the net vertical gravity change (in uGals) due to the effects of 
//           the sun and moon.  The GLT keyboard command toggles the display
//           on and off.  The values are also shown in the ZI zoom screen
//           display.  The GKx keyboard command controls the earth tide 
//           displacement and grvity offset plots.  If an external 
//           environmental sensor is used the GKx commands control the
//           sensor plots.  If a satellite is selected for plotting the GKx
//           commands control the sat az/el/signal level plots.
//
//           Added the /rx0 "gravity clock" operating mode.  This uses the
//           system clock as the time source.  It is optimized for showing
//           solid earth tide displacements and vertical gravity offsets.
//           To use this mode you must specify your location (via SL from 
//           the keyboard or the /po command line option or the "heather.loc"
//           file).
//
//           The color palette used for the lat/lon scattergram now repeats
//           every 12 hours (was 14 hours).  Colors 0, 1, and 2 are not used.
//           Using a 12 hour cycle is more appropriate since since it meshes
//           better with 24 hour days.  Also colors 1 and 2 are rather dim and
//           hard to see against a black background.
//
//           Added /cm=color,r,g,b command line option to change color map
//           table entries.
//
//           Added GpH command (where "p" is the plot selection character)
//           to calculate a histogram of the selected plot's value.  The
//           histogram is calculated over the values being displayed in the
//           plot window.  The histogram and FFT functions share much of the
//           same code and cannot be used at the same time.  The GF (FFT)
//           keyboard command is also used to disable a histogram plot.
//
//           Added /tsu command line fpr displaying the digital clock time
//           as Unix seconds.  The time is for the currently set local time
//           zone.  For actual Unix time, set the time zone offset to 0.
//
//           Added /tsg command line fpr displaying the digital clock time
//           as GPS seconds.  The time is for the currently set local time
//           zone.  For actual GPS time, set the time zone offset to 0.
//
//           Modified the automatic week number rollover correction code
//           to flush the plot queues if the rollover is detected within
//           20 seconds of starting the program.  This is so the bogus time
//           codes do not pollute the plot cursor time calculations.  The
//           20 second threshold allows receivers that just had a rollover 
//           occur to be analyzed... rollovers within the first 20 seconds
//           are assumed to be from a receiver that has had long standing
//           rollover issues.
//
//           Modified sun/moon position code to show the positions in YELLOW
//           if they are aligned well enough (0.75 degrees) to be an eclipse.
//           (currently only solar eclipses are detected).
//           Also modified sun/moon position history trail to show when the
//           sun/moon was below the horizon in GREY.
//
//           Fixed issue with end of daylight savings time possibly triggering
//           one hour early.
//
//           Added /dw date format command for showing dates in ISO week
//           format (yyyyWww-d)
//
//           Added SD command to calculate appoximate radio signal delay
//           between the GPS receiver and a remote station.  You enter the 
//           station lat and lon and the ionosphere height (approx 250 km 
//           in the winter and 350 km in the summer).  The SD command can also
//           be used to calculate the great circle distance and bearing 
//           between the current receiver lat/lon and a user specified
//           location.
//
//           Fixed issues parsing the RFTG-m status bytes.  Three of the
//           status bytes were not being converted from hex and the first 
//           status byte value was being interpreted for those status 
//           bytes... D'oh!
//
//           Added support for a "Big Ben" mode Westminster chime clock.
//           You will need to supply your own .WAV files for the hour
//           sequences and the quarters.
//
//           Added SU keyboard command to set the default UTC (leapsecond)
//           offset value that the receiver will use until it has the 
//           current value from the satellites.  This setting will be saved
//           in flash memory. This command is not supported for most receivers.
//
//           Modifed displays that show the sun with rays so that rays that  
//           fall outside of the clipping area for the display are not
//           shown. This minimizes trash left of the screen when the sun
//           moves away from the horizon.
//
//           Fixed zoomed displays that show satellite PRNs to not show PRNs
//           that are no longer active.  The previous version did not always
//           erase the old PRNs.
//
//           Modified satellite / sun / moon position history trail code to
//           use floating point az/el values (old version used integers).  If
//           the device reports satellite position as floating point numbers
//           the satellite trails will be a lot smoother.
//
//           Fixed an issue where the sun/moon trails on Raspberry Pi's 
//           were corrupted when the sun/moon was below the horizon (this 
//           issues seems to be due to a Ras Pi compiler bug).
//
//           Fixed an issue where if the log file name was given on the
//           command line (/wl=) before the receiver type (/rx) was specifed
//           the default file name for the receiver type overrode the user
//           specified log name.
//
//           Changed the way the automatic GPS date rollover correction works.
//           Before, once a rollover condition was detected (GPS repoted a
//           year <2016) the rollover correction was calculated and used from
//           then on.  The rollover code now does not "latch onto" a single
//           rollover correction value and will update the rollover correction
//           continuously.  This change helps if Heather is started before
//           the GPS receiver has finished initializing and is sending invalid
//           dates.  Once it starts sending valid dates, the old (bogus) 
//           rollover correction is canceled.  Also, Heather no longer waits
//           for the receiver to have a UTC leapsecond offset and it reports
//           a valid time for rollover compensation to be enabled.
//
//           Fixed the -1a, etc command line options that select Linux ACM/CDC
//           devices to use /dev/ttyACM0  (was using /dev/ACM0 which is not
//           available on a lot of distros)
//
//           Fixed configuring the GNSS system on Trimble multi-gnss devices.
//           Before it was not altering the GNSS system.
//
//           Changed Trimble ACE-III receiver type selector to /rxai.  Before
//           it was /rx3.  /rx3 now selects the Acutime 360 devices.
//
//           Modifed XML/GPX log files to set lat to 90.0 and lon to 90.0
//           if the location mode is set to "private" (GLP keyboard command)
//
//           When log files are closed all the statistics of the currently
//           displayed plot window's plot queue data are now written to the 
//           log file as comments.
//
//           Added support for getting the lat/lon/alt from the file
//           "heather.loc" if the receiver type does not have a GPS that
//           reports the device location.  The heather.loc file location can
//           also be used if you enter a value of "loc" when Heather requests
//           a lat/lon/alt location.
//
//           Changed NMEA echo port command to /ek (was /en)  and environmental
//           sensor (thermometer) port command to /en (was /et)... sorry for
//           any inconvienience.
//
//           Added display of tracked sat count number at the plot cursor
//           to the plot header (if it will fit on the screen)
//
//           If the mouse is placed over a satellite circle in a map display
//           the sat az/el/signal level will be shown below the map display
//           (but only if there is enough space on the screen to do it)
//
//           Added /so command line option to set the outline shape to draw
//           the sats in on the satellite maps.
//
//           Addded ability to simulate input from an "extra" interval counter
//           device using the /ri=filename command.  
//
//           The /h command line option now shows the command line help.
//           Earlier versions of Heather used /h=file to read in a .cfg
//           config file.  You now must use the /r=file.cfg command line
//           option to read config files.
//
//           Modified the order of the lines in the plot header info area.
//           All plot values are now on contiguos lines.  Note that if a
//           FFT or histogram plot is enabled and the mouse cursor is over
//           FFT or histogram data, and a plot review mode is active, it is 
//           posible that the top line of the histogram/FFT info can oveflow
//           into the plot review line.
//
//           Modifed the code that shows the plot data at the mouse cursor
//           to show the time in RED if it is at a time stamp sequence error.
//           The mouse cursor data is normally show in CYAN.
//
//           Modified Ublox code to automatically send RAW data messages every
//           second or at the requested raw data rate (previously these were 
//           only requested by the message polling loop).  
//
//           Fixed an issue where a precision survey would be aborted if the
//           receiver had a com message timeout during the survey.
//
//
//           Changed the satellite information table display routines.
//           If more satellies are visible than can fit on the screen, a
//           message is shown.
//
//           The satellite PRN is followed by a character that indicates
//           which GNSS system the satellite belongs to.  They follow the
//           RINEX standard for designating satellite systems.
//
//           Changed the GCT command to control display of only tracked sats.
//           Earlier version of Heather used GCT as an alias of the SI
//           satellite info table format command.
//
//           Added ability to sort the table on carrier phase, pseudorange,
//           clock bias, and state.  Invalid or missing values are always
//           sorted to the bottom of the table.
//
//           Made the satellite count plot a standard plot with plot 
//           statisics, etc available.  You can control it with the G$ or 
//           GCG keyboard commands.  The sat count plot does not scale or
//           center.  It is always at the bottom of the plot area.
//
//           Changed the auto-detect data collection timeout code to work 
//           better with X11 systems.  It now completes the data collection
//           after the intended 3 seconds.  It was taking much longer due to
//           continuous screen updates.
//
//           Modified time zone / daylight savings time code to automatically
//           set the DST zone to 2 (Uk/Europe) if the time zone name for
//           daylight savings time is set to "BST" and the DST zone has not
//           been specified by the user with the /b= command line option.
//
//
//
//           Added support for writing RINEX format log files if the receiver
//           supports raw satellite observation data output (doppler, carrier
//           phase, pseudorange).  To write a RINEX file, specify a log file
//           name with the ".obs" extension.  RINEX files can be submitted to
//           GPS data processing services to get much more precise location
//           information.  Currently the best processing service seems to
//           be CSRS-PPP (in Canada).  They can handle single frequency
//           receiver data files (but they only seem to use the pseudorange
//           measurements).
//
//           Added /rr command line option for controlling output rate of
//           raw data messages.  Defaults to 1 second, but raw data can cause
//           a lot of traffic from the receiver.  Raw data messages are
//           are mainly used by post-processing programs for calculating
//           very precise position and time solutions.
//
//           Added /rm command line option for setting the raw measurment
//           types to include in RINEX files.
//
//           Added /at command line option for setting the antenna type
//
//           Added /an command line option for setting the antenna number
//
//           Added /ah command line option for setting the antenna height
//           (and optionally e/w and n/s displacements) to include in RINEX 
//           files.
//
//           Added /ak command line option for setting the marker name
//           string to include in RINEX files.
//
//           Added /av command line option for setting the marker number
//           string to include in RINEX files.
//
//           Modified default plots for the TruePosition receivers to show
//           the EFC DAC value (GD) and hide the undocumented EVAL value (G8).
//           Also changed the scale factor for the DAC plot to be in uV/div.
//
//           Added the GLA command to autoscale the LLA scattergram scale
//           factor.  This can be useful if you are using the receiver in
//           a moving environment.
//
//           Added the SQ command to enable plotting of a single satellite's
//           or sun or moon azimuth, elevation, and signal level.  If SQ mode
//           is enabled, the earth tide plots are not available.  The GK
//           command is used to enable/disable plots.  This SQ mode is not
//           available when an envronmental sensor is being used.
//
//           Added the LP/WLP command to enable writing a satellite PRN info
//           log file of the tracked satellites time/prn/azimuth/elevation
//           info (the time is in JD UTC format).
//
//           Fixed LLA scattergram rendering code to invert north/south and
//           east/west directions.
//
//           Modified the code that guesses the UTC offset (leapsecond count)
//           for receivers that don't support leapsecond output to assume the
//           next leapsecond (#19) will be on 1 JUL 2019.
//
//           If the receiver does not send gps week or time-of-week data
//           then these values are calculated from the time.  If this is done
//           the WEEK: and TOW: values will be shown in YELLOW.
//
//           Changed UCCM GPSDO message parser to (hopefully) work with the
//           Ublox LEA-6T / Samsung oscillator versions of the GPSDO.
//
//           Fixed (hopefully) the CT plot queue trim commands.  CTE and  CTS 
//           were not always working properly.
//
//           Reworked the code that shows the alarms and receiver state column
//           to maximize the amount of information that can fit on the screen.
//
//           Modifed the satellite PRN maximum signal level table (shown when
//           the '&' menu is active) to show all sats.  Previously only PRNs
//           1..32 were shown.  If no sats in a row have signal levels
//           detected then that row is not shown.
//
//           Modified the format of the "#SIG" satellite constellation lines
//           in ASCII log files to include: PRN, AZ, EL, SIG, DOPPLER,
//           CODE or CARRIER PHASE, PSEUDORANGE, CLOCK BIAS.  I'm sorry if
//           this change breaks any of your current log readers... .XML log
//           files are much better about indicating what the various data
//           values are (but, alas, are larger and harder to read).
//
//           Modified the default title bar string to include the executable
//           file name along with the receiver type.
//
//           Added a RPN calculator mode: "`" (backwards quote) keyboard
//           keyboard command.  Also Z` will bring up the calculator in a
//           zoomed full screen mode.  The /rxca command line option selects
//           a "calculator only" mode.
//
//           Added support for New Years song that plays at 00:00:01 on
//           1 Jan.
//
//           Added ability to show altitude in standard linguini (7.1429 lg 
//           per meter) with /tlg command line option or GLL keyboard command,
//
//           Added /wt[=#] command line option to select the type of hands 
//           to draw the analog watch with.  Default hand shape is now
//           filled trapazoidal hands.
//
//
//  Other (mostly rather obscure) keyboard selctable options:
//  Those marked with "---" are either no longer implemented or have proper
//  keyboard or command line options to do what they did.  Their function 
//  is very likely to be changed in later versions.
//
//    OA   - toggle AMU vs dBc signal level displays.
//    OB # - set ADEV bins per decade
//    OC   - toggle continuous plot scrolling mode.  In non-scrolling mode
//           the plot queue arrows are shown in CYAN instead of WHITE)
//           The (dafault) continuous scroll mode scrolls the plot left one
//           pixel as each new point comes in.  In non-scrolling mode, the
//           plot scrolls left two major divisions whenever it reaches the
//           right edge.  Also the ADEV tables are only updated every 10
//           seconds.  Non-scrolling mode was intended for use on very 
//           slow systems.
//    OD   - toggle FFT plot display in dB or raw values
//    OE   - toggle Thunderbolt-E display mode
//    OF   - toggle periodic refresh of adev calculations
//    OG   - set solid earth tide options:  bit 0x01 set = use original solid.f
//           sun/moon position   bit 0x02 set = calculate mean tides by restoring
//           permament earth tide deformations.
//    OH   - toggle erasing of Lat/Lon/Alt survery plot every hour
//--- OI # - set signal level display type
//    OJ # - toggle logging of serial port data stream
//    OK   - toggle logging of TSIP message faults as time skips
//    OL   - toggle live FFT / Histogram mode
//    OM # - set plot magnification factor
//    ON   - toggle real-time update of trend line plot title
//    OP   - toggle plot scaling mode to peak value seen
//    OQ   - toggle plot queue sampling fast / slow mode
//--- OR   - reset ADEV bins and recalculate ADEVs
//    OS # - toggle temperature spike filter mode
//    OT   - toggle alarm/dump/exit time triggers to be based upon local time
//           (default) or displayed time which can be in one of the 
//           astronomical time scales.  Previous versions used OT to toggle
//           12/24 hour clock mode which is now available from the T menu.
//--- OU # - set daylight savings time area number (0 .. 5)
//    OV # - toggle ADEV base value mode
//--- OW # - select analog watch face type (0 .. 5)
//    OX # - set trend line rate display time scale (0=units per day, 1=per hour, 2=per minute, 3=per second)
//--- OY # - set tempurature-dac plot (G3 plot) scale factor
//    OZ # - toggle plot cursor time reference between start of capture <hms> 
//           and start displayed data [hms]  You can also force the time
//           to be in seconds by setting the OZ value to 2 for <seconds> or 
//           to 3 for [seconds]
//
//
//
//
//  This program requires the following operating system dependent routines:
//
//  init_hardware() - put screen in a high res graphics mode or open a 
//                    graphics window and open the com port (9600,8,N,1)
//
//  dot(x,y, color) - draw a colored dot
//
//  get_pixel(x,y) - read a pixel from the screen
//
//  kill_screen() - close graphics screen or window
//
//  sendout()  - send byte 'c' to the serial port
//
//  SERIAL_DATA_AVAILABLE() - a routine or macro that returns true if 
//                            there is serial port data available
//
//  get_serial_char()  - get a character from the serial port.  You should check
//                       SERIAL_DATA_AVAILABLE() befor calling this.
//
//  kill_com()    - close down serial port
//
//  SetDtrLine(state) - used for PWM fan control for temerature control PID
//  SetRtsLine(state) - used for PWM fan control for temerature control PID 
//  SetBreak(state)   - used to wake up Nortel GPSDO's by sending a BREAK condition
//
//  KBHIT() - a routine or macro that returns true if a keyboard key has
//            been pressed
//
//  GETCH() - a routine or macro that returns the keyboard character
//
//  refresh_page() - copy any virtual screen buffer to the screen
//                   or flip pages if doing screen buffering.  Can be
//                   a null routine if writing directly to the screen.
//
//  BEEP() - sound a beep if beep_on is set
//
//
//  set_cpu_clock() - has OS dependent code for setting the system time
//
//  GetMsecs() - returns a double precision count of milliseconds. Can
//               be since program started,  os boot, or any base time
//               reference (used to do pwm control of the heat/cool cycle
//               if doing precise temp control and checking for loss of
//               serial port communications. Also sets wall_time variable
//               to system clock time with high resolution.
//
//  GetNsecs() - return high resolution timer count in nanoseconds.
//
//  Also the get_mouse_info() routine will need to be updated to handle
//  the system mouse.  You need to get the current mouse coordinates into
//  variables mouse_x and mouse_y and the button state into this_button.
//
//  play_tune() - play a sound file asynchronously (non-blocking)
//
//  Also, you can improve performance with operating system dependent
//  line and circle drawing and area erasing functions.
//
//  To see where you might need to add support for a new operating system
//  search the code for the strings:
//    WINDOWS     (Windows related stuff)
//    __linux__   (Linux related stuff)
//    __MACH__    (macOS OS/X related stuff)
//    __FreeBSD__ (FreeBSD related stuff)
//    WIN_VFX     (Windows video/keyboard/mouse stuff)
//    USE_X11     (X11 video/keyboard/mouse stuff for Linux and OS/X)
//
//  If adding a new receiver type search for NEW_RCVR.  This flags routine
//  that will almost certainly need to be updated for the new receiver type.
//  (there are also lots of other places that will probably need updating)
//
//
// Note: stupid DOS linker does not allow initialized variables to be declared
//       in more than one file (even if defined as externs).  Therefore any
//       variables that are used in more than one file are initialized
//       to non-zero values in the routine set_defaults();
//
//