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drvTip810.html
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<HTML>
<HEAD>
<TITLE>drvTip810 - CAN Bus Driver </TITLE>
<META NAME="Author" CONTENT="Andrew Johnson">
<META NAME="Description" CONTENT="How to use the Tip810 CANbus driver software">
<META NAME="KeyWords" CONTENT="vxWorks, EPICS, CANbus, TEWS, tip810">
<META NAME="Version" CONTENT="$Id: drvTip810.html,v 1.9 2003-11-13 21:41:33 anj Exp $">
</HEAD>
<BODY>
<H1 ALIGN=CENTER>drvTip810 - CAN Bus Driver </H1>
<CENTER><P>TEWS Tip810 Driver for EPICS<BR>
Version 2.6</P></CENTER>
<CENTER><ADDRESS>Andrew Johnson
<A HREF="mailto:anj@aps.anl.gov"><anj@aps.anl.gov></A>
</ADDRESS></CENTER>
<UL>
<LI><A HREF="#section1">Introduction</A> </LI>
<LI><A HREF="#section2">Tip810 Driver Usage</A></LI>
<UL>
<LI><A HREF="#t810Create">t810Create</A> </LI>
<LI><A HREF="#t810Shutdown">t810Shutdown</A> </LI>
<LI><A HREF="#t810Initialise">t810Initialise</A> </LI>
<LI><A HREF="#t810Report">t810Report</A> </LI>
<LI><A HREF="#canTest">canTest</A> </LI>
</UL>
<LI><A HREF="#section3">Routines for CANbus Applications</A></LI>
<UL>
<LI><A HREF="#canOpen">canOpen</A> </LI>
<LI><A HREF="#canIoParse">canIoParse</A> </LI>
<LI><A HREF="#canWrite">canWrite</A> </LI>
<LI><A HREF="#canMessage">canMessage</A> </LI>
<LI><A HREF="#canMsgDelete">canMsgDelete</A> </LI>
<LI><A HREF="#canSignal">canSignal</A> </LI>
<LI><A HREF="#canBusReset">canBusReset</A> </LI>
<LI><A HREF="#canBusStop">canBusStop</A> </LI>
<LI><A HREF="#canBusRestart">canBusRestart</A> </LI>
<LI><A HREF="#canRead">canRead</A> </LI>
</UL>
</UL>
<P><HR></P>
<H2><A NAME="section1"></A>1. Introduction</H2>
<P>This document describes the software interface to the TEWS TIP810
Industry-Pack Module for vxWorks, written as part of an EPICS interface to
the CANbus for the <A HREF="http://www.gemini.edu/">Gemini</A> and
<A HREF="http://www.jach.hawaii.edu/UKIRT/home.html">UKIRT</A> telescopes.
This software is an IPAC Module Driver and uses the services of the drvIpac
Industry Pack Driver to interface to the IPAC Carrier Board - see the
accompanying document <A HREF="drvIpac.html">drvIpac - Industry Pack
Driver</A> for details of this driver software. The device support routines
provided for use with EPICS are described in the document
<A HREF="devCan.html">devCan - CAN Bus Device Support</A> which briefly covers
the use of the various record types supported. </P>
<P>The following routines provided by this driver are described in detail
below: </P>
<UL>
<LI><A HREF="#t810Create">t810Create</A> </LI>
<LI><A HREF="#t810Shutdown">t810Shutdown</A> </LI>
<LI><A HREF="#t810Initialise">t810Initialise</A> </LI>
<LI><A HREF="#t810Report">t810Report</A> </LI>
<LI><A HREF="#canTest">canTest</A> </LI>
<LI><A HREF="#canOpen">canOpen</A> </LI>
<LI><A HREF="#canIoParse">canIoParse</A> </LI>
<LI><A HREF="#canWrite">canWrite</A> </LI>
<LI><A HREF="#canMessage">canMessage</A> </LI>
<LI><A HREF="#canMsgDelete">canMsgDelete</A> </LI>
<LI><A HREF="#canSignal">canSignal</A> </LI>
<LI><A HREF="#canBusReset">canBusReset</A> </LI>
<LI><A HREF="#canBusStop">canBusStop</A> </LI>
<LI><A HREF="#canBusRestart">canBusRestart</A> </LI>
<LI><A HREF="#canRead">canRead</A> </LI>
</UL>
<P><HR></P>
<H2><A NAME="section2"></A>2. Tip810 Driver Usage</H2>
<P>The software provides an interface to higher level software which, other
than device initialisation, is not specific to the TIP810 but could be used
with a CANbus driver for a different hardware interface. The interface to the
higher level software is provided in two header files: <I>canBus.h</I>
contains all of the generic CANbus definitions and declarations, while
<I>drvTip810.h</I> incorporates the additional declarations and definitions
which are specific to the TIP810 module (and also <TT>#include</TT>s
<I>canBus.h</I> and the vxWorks ANSI header file <I>types.h</I>). The
routines which are specific to the TIP810 or meant for use from the vxWorks
shell are described individually in this section, while the generic CANbus
interface routines are described in <A HREF="#section3">section 3</A> below.
</P>
<P>The TEWS TIP810 IP module contains a Philips pca82c200 stand-alone
CAN-controller chip which performs all of the CANbus interfacing functions.
The interface to this chip is defined in a separate header file
<I>pca82c200.h</I> which declares the register interface structure and the
bit-patterns for the various chip registers. </P>
<P>The driver uses an interrupt service routine with a different interrupt
vector for each TIP810 module it controls, starting with vector 0x60 and
increasing by one each time. </P>
<P>The driver can be built for use in a native vxWorks (i.e. non-EPICS)
application. To do this, the <I>drvTip810.c</I> file should be compiled with
the <B><TT>-DNO_EPICS</TT></B> switch to disable the EPICS-specific code. </P>
<P><HR></P>
<H3><A NAME="t810Create"></A>t810Create</H3>
<P>Registers a new TIP810 device with the driver. In EPICS, this is registered
as an iocsh command.</P>
<PRE>int t810Create (char *pbusName, ushort_t card, ushort_t slot,
ushort_t irqNum, uint_t busRate);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>char *pbusName</TT> </DT>
<DD>String which comprises a unique identifier for this particular CAN Bus.
This must be a static string which should not be changed while the driver is
loaded and running (vxWorks shell string literals have this property).
While <TT>t810Create</TT> enforces no restrictions on the characters which
may be used in the name, if the <TT>canIoParse</TT> routine is used the name
should contain alphanumeric characters only. </DD>
<DT><TT>ushort_t card, ushort_t slot</TT> </DT>
<DD>Ipac Driver carrier and slot numbers which identify the IPAC module,
for use with drvIpac. </DD>
<DT><TT>ushort_t irqNum</TT> </DT>
<DD>Interrupt vector number. Previous versions of the driver automatically
allocated vectors numbers starring at 0x60, but these should really be set by
the user, hence the addition of this parameter. </DD>
<DT><TT>uint_t busRate</TT> </DT>
<DD>CAN bus rate in Kbits/sec. This parameter can have one of the values
given in the following table. Other rates will require modifications to
the driver source code. The Kvaser standard uses different bit timings
which are not compatible with those used by Tews and so require special
bit-rate entries. </DD>
</DL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B><TT>busRate</TT></B></TD>
<TD><B><I>CANbus bit rate</I></B></TD>
</TR>
<TR>
<TD> 5</TD>
<TD>5 Kbits/sec</TD>
</TR>
<TR>
<TD> 10</TD>
<TD>10 Kbits/sec</TD>
</TR>
<TR>
<TD> 20</TD>
<TD>20 Kbits/sec</TD>
</TR>
<TR>
<TD> 50</TD>
<TD>50 Kbits/sec</TD>
</TR>
<TR>
<TD> 100</TD>
<TD>100 Kbits/sec</TD>
</TR>
<TR>
<TD> 125</TD>
<TD>125 Kbits/sec</TD>
</TR>
<TR>
<TD> 250</TD>
<TD>250 Kbits/sec</TD>
</TR>
<TR>
<TD> 500</TD>
<TD>500 Kbits/sec</TD>
</TR>
<TR>
<TD> 1000</TD>
<TD>1000 Kbits/sec</TD>
</TR>
<TR>
<TD> 1600</TD>
<TD>1600 Kbits/sec</TD>
</TR>
<TR>
<TD> -125</TD>
<TD>Kvaser 125 Kbits/sec</TD>
</TR>
<TR>
<TD> -250</TD>
<TD>Kvaser 250 Kbits/sec</TD>
</TR>
<TR>
<TD> -500</TD>
<TD>Kvaser 500 Kbits/sec</TD>
</TR>
<TR>
<TD> -1000</TD>
<TD>Kvaser 1000 Kbits/sec</TD>
</TR>
</TABLE></CENTER>
<H4>Description</H4>
<P>This routine will usually be called from the vxWorks (EPICS) start-up
script. It is used to inform the driver about each TIP810 module which
it is to control, providing information on how to find the module (the
IPAC carrier and slot numbers) and what CANbus bit rate is to be used.
Each module is given a name which is matched during calls to the <TT>canOpen</TT>
routine to identify the particular module again. </P>
<P>The code checks that the given name and card/slot numbers are unique
and point to a real Tews Tip810 module, then it creates a new device table
and initialises it and some of the chip registers. At this stage the device
is not activated but held in the reset state. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<DL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>S_t810_badBusRate</TD>
<TD>Bus Rate not supported</TD>
</TR>
<TR>
<TD>S_t810_duplicateDevice</TD>
<TD>another TIP810 already using given name and/or IPAC address </TD>
</TR>
<TR>
<TD>(drvIpac)</TD>
<TD>errors returned by <TT>ipmValidate</TT> </TD>
</TR>
<TR>
<TD>(vxWorks)</TD>
<TD>errno from <TT>malloc</TT>, <TT>semBCreate</TT>, or <TT>semMCreate</TT></TD>
</TR>
</TABLE></CENTER>
</DL>
<H4>Example</H4>
<UL>
<PRE>-> t810Create("CAN1", 0, 1, 500)
Value = 0</PRE>
</UL>
<P><HR></P>
<H3><A NAME="t810Shutdown"></A>t810Shutdown</H3>
<P>Reboot hook routine, resets all devices to stop interrupts. </P>
<PRE>int t810Shutdown(int startType);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>int startType</TT> </DT>
<DD>This parameter is not used by the routine but is
required to allow it to be used as a vxWorks reboot hook routine,
when it differentiates between a cold and a warm restart. </DD>
</DL>
<H4>Description</H4>
<P>When <TT>t810Initialise</TT> is run, this routine will be connected
up to the vxWorks reboot hook to reset the CAN controller chips on all
known TIP810 modules when the system is rebooted. It can also be called
by applications programs to turn off all the module drivers in the event
of a catastrophic failure, but it may be necessary to reboot the system
to re-enable them afterwards. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>S_t810_badDevice </TD>
<TD>Bad or corrupted internal device table found</TD>
</TR>
</TABLE></CENTER>
<P><HR></P>
<H3><A NAME="t810Initialise"></A>t810Initialise</H3>
<P>Initialise driver and all registered hardware. </P>
<PRE>int t810Initialise(void);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>void</TT> </DT>
<DD>None. </DD>
</DL>
<H4>Description</H4>
<P>Under EPICS this routine is called during <TT>iocInit</TT>, which must occur
after all <TT>canCreate</TT> calls in the start-up script. It creates a message
queue to hold received messages and starts a task named <TT>canRecvTask</TT> to
distribute them to the routines that have asked to be informed about them.
Finally it completes the initialisation of the CAN controller chip and
interrupt vector registers for all known TIP810 devices and starts them
running. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>(vxWorks)</TD>
<TD>errno from <TT>intConnect</TT></TD>
</TR>
</TABLE></CENTER>
<P><HR></P>
<H3><A NAME="t810Report"></A>t810Report</H3>
<P>Display report giving status of all TEWS Tip810 devices. In EPICS, this is
registered as an iocsh command.</P>
<PRE>int t810Report(int interest);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>int interest</TT> </DT>
<DD>Interest level, indicating how much detail is required and what information
to show. </DD>
</DL>
<H4>Description</H4>
<P>Outputs (to stdout) a list of all the Tip810 devices created, their
IP carrier & slot numbers and the bus name string. For <TT>interest=1</TT>
it adds message and error statistics; for <TT>interest=2</TT> it lists
all CAN IDs for which a call-back has been registered; for <TT>interest=3</TT>
the status of the CAN controller chip is given. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>S_t810_badDevice </TD>
<TD>Bad or corrupted internal device table found</TD>
</TR>
</TABLE></CENTER>
<H4>Examples</H4>
<UL>
<PRE>-> t810Report(1)
TEWS tip810 CANbus Ip Modules
'CAN1' : IP Carrier 0 Slot 1, bus rate 500 Kbits/sec
Messages Sent : 75
Messages Received : 43
Message Overruns : 0
Discarded Messages : 4
Last Discarded ID : 0x206
Error Interrupts : 0
Bus Off Events : 0
-> t810Report(2)
TEWS tip810 CANbus Ip Modules
'CAN1' : IP Carrier 0 Slot 1, bus rate 500 Kbits/sec
Callbacks registered:
0x1c 0x1d 0x1e 0x1f 0x200 0x202 0x204
canRead Status : Idle
-> t810Report(3)
TEWS tip810 CANbus Ip Modules
'CAN1' : IP Carrier 0 Slot 1, bus rate 500 Kbits/sec
pca82c200 Chip Status:
Bus Status : Bus-On
Error Status : Ok
Data Overrun : Ok
Receive Status : Idle
Receive Buffer Status : Empty
Transmit Status : Idle
Transmission Complete : Complete
Transmit Buffer Access : Released</PRE>
</UL>
<P><HR></P>
<H3><A NAME="canTest"></A>canTest</H3>
<P>Test routine, sends a single test message to the named CANbus. </P>
<PRE>int canTest (char *pbusName, ushort_t identifier, ushort_t rtr,
uchar_t length, char *data);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>char *pbusName</TT> </DT>
<DD>Device name to identify the particular T810 device to use. </DD>
<DT><TT>ushort_t identifier</TT> </DT>
<DD>The CANbus message identifier to send. </DD>
<DT><TT>ushort_t rtr</TT> </DT>
<DD>0 for a normal CAN message, non-zero to send a Remote Transmission
Request packet. </DD>
<DT><TT>uchar_t length</TT> </DT>
<DD>Number of bytes in the data field for this CANbus message type. </DD>
<DT><TT>char *data</TT> </DT>
<DD>Pointer to the data to be sent. Ignored for RTR packets. </DD>
</DL>
<H4>Description</H4>
<P>This routine is provided as a diagnostic, to allow the system developer
to generate CANbus messages and RTR packets from the vxWorks shell. It
should not be used from within an application. It makes use of the <TT>canOpen</TT>
and <TT>canWrite</TT> routines, and responds to errors reported by those
routines by printing a message and returning -1. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>-1</TD>
<TD>ERROR</TD>
</TR>
</TABLE></CENTER>
<H4>Example</H4>
<UL>
<PRE>-> canTest "CAN1", 0x33, 0, 4, "STOP"</PRE>
</UL>
<P><HR></P>
<H2><A NAME="section3"></A>3. Routines for CANbus Applications </H2>
<H3><A NAME="canOpen"></A>canOpen</H3>
<P>Return device pointer for given CAN bus name. </P>
<PRE>int canOpen(char *busName, void **pcanBusID);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>char *busName</TT> </DT>
<DD>Device name to identify the particular Tip810 device to use. </DD>
<DT><TT>void **pcanBusID</TT> </DT>
<DD>Pointer to a void* location to hold the device identifier. </DD>
</DL>
<H4>Description</H4>
<P>Searches through the list of registered Tip810 devices for one which
matches the name given, and returns a device identifier for it. This identifier
is a required parameter for all of the remaining can driver routines. String
searching in this manner is not particularly fast if several devices have
been registered so this routine is intended to be used mainly when an application
starts up. It may be used as often as desired however - there is no associated
<TT>canClose</TT> routine. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>S_can_noDevice</TD>
<TD>No matching device name found.</TD>
</TR>
</TABLE></CENTER>
<H4>Example</H4>
<UL>
<PRE>void *can1;
if (canOpen("CAN1", &can1)) {
printf("Can't open CAN1\n");
return -1;
}</PRE>
</UL>
<P><HR></P>
<H3><A NAME="canIoParse"></A>canIoParse</H3>
<P>Parse a CAN address string into a canIo_t structure </P>
<PRE>int canIoParse(char *canString, canIo_t *pcanIo);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>const char *canString</TT> </DT>
<DD>Address string to be converted. </DD>
<DT><TT>canIo_t *pcanIo</TT> </DT>
<DD>Pointer to a structure which will be used to return the converted address
information. </DD>
</DL>
<H4>Description</H4>
<P><TT>canIoParse</TT> is used by the EPICS device support routines to
convert record hardware addresses, but can be used by any application with
similar requirements. It is intended to provide a standard way of converting
the parameters which are needed to specify a portion of a particular CANbus
message type from an ASCII string to their binary representation as a structure.
The <TT>canIo_t</TT> structure is defined as a typedef in the canBus.h
header as follows: </P>
<UL>
<PRE>typedef struct {
char *busName;
int timeout;
ushort_t identifier;
ushort_t offset;
long parameter;
char *paramStr;
void *canBusID;
} canIo_t;</PRE>
</UL>
<P>The address string passed to this routine consists of a series of elements,
some of which are optional. </P>
<UL>
<I>busName</I>[<TT><B>/</B></TT><I>timeout</I>]<TT><B>:</B></TT><I>identifier</I>[<TT><B>+</B></TT><I>n</I>..][<TT><B>.</B></TT><I>offset</I>]<I>parameter</I>
</UL>
<P>The first element is the bus name, which should consist of alphanumeric
characters only. The name is terminated immediately before the first "<TT>/</TT>"
or "<TT>:</TT>" character in the string, and after omitting any
leading white-space the characters forming the bus name are copied to a
newly allocated buffer, the address of which is placed in <TT>pcanIo->busName</TT>.
</P>
<P>An oblique stroke ("<TT>/</TT>") after the bus name introduces
an optional timeout element, which is an integer number of milli-seconds
to wait for a response for this particular type of message. This is converted
into vxWorks system clock ticks and placed in <TT>pcanIo->timeout</TT>.
If no timeout element is included, the timeout is set to <TT>WAIT_FOREVER</TT>
(-1). </P>
<P>The CANbus message identifier is preceded by a colon
("<TT>:</TT>"), and must result in one of the legal CANbus
identifiers in the range 0 through 2047 (with holes). The identifier itself can
be specified as a single number, or in several parts separated by plus signs,
which are all summed. The numbers here can be given in any of the standard 'C'
formats as converted by <TT>strtol</TT>, so negative, hex or octal numbers may
be used as desired. </P>
<P>If the identifier is followed by a decimal point ("<TT>.</TT>"),
the following element is an optional byte offset into the CANbus message.
The offset is an unsigned short integer (using <TT>strtoul</TT> again for
the conversion), although to remain within the limits of the message buffer
it should be restricted to a maximum value of seven. The converted value
is placed in <TT>pcanIo->offset</TT>, which defaults to zero if no offset
is given. </P>
<P>The final element is a general-purpose parameter, introduced by a space or
tab character. The value is first converted to a signed long using
<TT>strtol</TT> which is placed in <TT>pcanIo->parameter</TT>. A pointer to
any remaining characters is placed in <TT>pcanIo->paramStr</TT>.</P>
<P>If the string is successfully converted without errors, canIoParse will
also call <TT>canOpen</TT> to initialise the <TT>pcanIo->canBusID</TT>
bus identifier. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>S_can_badAddress</TD>
<TD>illegal input string or NULL input parameters</TD>
</TR>
<TR>
<TD>S_can_noDevice</TD>
<TD>No matching device name found</TD>
</TR>
<TR>
<TD>(vxWorks)</TD>
<TD>errno from <TT>malloc</TT></TD>
</TR>
</TABLE></CENTER>
<H4>Example</H4>
<UL>
<PRE>canIo_t myIo;
int status;
status = canIoParse("CAN1/20:0126.4 0xfff", &myIo)
if (status) {
printf("Address string rejected\n");
return -1;
}</PRE>
</UL>
<P><HR></P>
<H3><A NAME="canWrite"></A>canWrite</H3>
<P>Writes a message to the given CANbus </P>
<PRE>int canWrite (void *canBusID, canMessage_t *pmessage, int timeout);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>void *canBusID</TT> </DT>
<DD>CANbus device identifier, obtained from <TT>canOpen</TT> </DD>
<DT><TT>canMessage_t *pmessage</TT> </DT>
<DD>The message to be transmitted. </DD>
<DT><TT>int timeout</TT> </DT>
<DD>Delay in vxWorks system clock ticks, indicating how long to wait for
exclusive access to the TIP810 hardware. </DD>
</DL>
<H4>Description</H4>
<P>This routine is called to transmit a message on a particular CANbus.
The <TT>canMessage_t</TT> type is defined as the following structure in
canBus.h: </P>
<UL>
<PRE>typedef struct {
short_t identifier; /* 0 .. 2047 with holes! */
enum {
SEND = 0, RTR = 1
} rtr; /* Remote Transmission Request */
uchar_t length; /* 0 .. 8 */
uchar_t data[CAN_DATA_SIZE]; /* CAN_DATA_SIZE = 8 */
} canMessage_t;</PRE>
</UL>
<P>When called, <TT>canWrite</TT> obtains exclusive access to the TIP810
transmission buffer, converts the message into the correct form for the
interface chip and copies it to the hardware registers. Finally it sends
a Transmit Message command to the chip. The exclusive access semaphore
will be released by the Interrupt Service Routine when it receives a notification
from the chip that the message has been transmitted successfully. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>S_t810_badDevice</TD>
<TD>canBusID not valid</TD>
</TR>
<TR>
<TD>S_can_badMessage</TD>
<TD>invalid field in the message buffer</TD>
</TR>
<TR>
<TD>S_t810_transmitterBusy</TD>
<TD>system fault somewhere</TD>
</TR>
<TR>
<TD>(vxWorks)</TD>
<TD>errno from <TT>semTake</TT></TD>
</TR>
</TABLE></CENTER>
<H4>Example</H4>
<UL>
<PRE>canIo_t myIo;
canMessage_t message;
char data[] = "STOP";
int status;
status = canIoParse("CAN1/20:0126 0xfff", &myIo);
if (status == OK) {
message.identifier = myIo.identifier;
message.rtr = SEND;
message.length = strlen(data);
memcpy(&message.data[0], data, message.length);
status = canWrite(myIo.canBusID, &message, myIo.timeout);
}</PRE>
</UL>
<P><HR></P>
<H3><A NAME="canMessage"></A>canMessage</H3>
<P>Register CAN message call-back </P>
<PRE>int canMessage(void *canBusID, ushort_t identifier,
canMsgCallback_t *pcallback, void *pprivate);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>void *canBusID</TT> </DT>
<DD>CANbus device identifier, obtained from <TT>canOpen</TT> </DD>
<DT><TT>ushort_t identifier</TT> </DT>
<DD>The CAN message identifier for which call-backs are required. </DD>
<DT><TT>canMsgCallback_t *pcallback</TT> </DT>
<DD>The address of the routine to be called whenever matching messages
are received. </DD>
<DT><TT>void *pprivate</TT> </DT>
<DD>A parameter which is passed to the call-back routine to help it identify
its context. </DD>
</DL>
<H4>Description</H4>
<P>This routine is used to add a call-back routine for a particular CAN message
identifier on the given CANbus. Call-backs can be registered for any CAN
message identifier, and there can be more than one call-back using the same ID
- all routines are called in turn when a message with the relevant identifier
is received. The call-back routine must not change the message at all, and
should copy any information it needs from the message buffer before returning.
The call-back used to be executed from vxWorks' Interrupt Context, thus there
were restrictions in what vxWorks routines the call-back could use (see the
vxWorks User Guide for details of these), however from release 2-1 a high
priority task is used instead. Processing should still be kept to a minimum
though as this task is run at a high priority. The call-back routine should be
of type <TT>canMsgCallback_t</TT>: </P>
<PRE>void callback(void *pprivate, const canMessage_t *pmessage);</PRE>
<P>The same <TT>pprivate</TT> value supplied when the call-back was registered
with <TT>canMessage</TT> is passed to the call-back routine with each message
to allow it to identify its context. </P>
<H4>Returns</H4>
<UL>
<PRE>int</PRE>
</UL>
<CENTER><TABLE BORDER=1 >
<TR BGCOLOR="#FFFFFF">
<TD><B>Symbol/Value</B></TD>
<TD><B>Meaning</B></TD>
</TR>
<TR>
<TD>0</TD>
<TD>OK</TD>
</TR>
<TR>
<TD>S_can_badMessage</TD>
<TD>bad identifier or NULL call-back routine</TD>
</TR>
<TR>
<TD>S_can_badDevice</TD>
<TD>bad device pointer</TD>
</TR>
<TR>
<TD>(vxWorks)</TD>
<TD>errno from <TT>malloc</TT></TD>
</TR>
</TABLE></CENTER>
<H4>Example</H4>
<UL>
<PRE>void myCallback(short *pvalue, canMessage_t *pmessage) {
/* Update value whenever message arrives */
memcpy(pvalue, &pmessage->data[0], sizeof(short));
}
...
int status;
static short value;
status = canMessage(myIo.canBusID, myIo.identifier,
(canMsgCallback_t *) myCallback, &value);</PRE>
</UL>
<P><HR></P>
<H3><A NAME="canMsgDelete"></A>canMsgDelete</H3>
<P>Delete CAN message call-back</P>
<PRE>int canMsgDelete(void *canBusID, ushort_t identifier,
canMsgCallback_t *pcallback, void *pprivate);</PRE>
<H4>Parameters</H4>
<DL>
<DT><TT>void *canBusID</TT> </DT>
<DD>CANbus device identifier, obtained from <TT>canOpen</TT> </DD>
<DT><TT>ushort_t identifier</TT> </DT>
<DD>The CAN message identifier for which call-backs were registered.</DD>
<DT><TT>canMsgCallback_t *pcallback</TT> </DT>