pi-rtk

The files and instructions to get a rtklib RTK base station running on a Raspberry Pi

Hardware requirements

• Raspberry Pi Model b (I've used a Pi3)
• 8GB Micro SD card (I've used a Sandisk MAX ENDURANCE card)
• U-blox GPS module that supports RXM-RAWX output (I've used a Neo-M8T)
• 4g USB dongle (Huawei Unlocked E3372h)

Prerequisites

Seeing as the Pi will most likely operate as a headless server, I've opted to setup everything from the get-go via SSH.

• A knowledge of the Linux (Raspberry Pi OS is based on Debian) command line interface (CLI)
• An SSH client PuTTY is a good one for Windows

Initial setup

1. Download Raspberyy Pi OS Lite from the Raspberry Pi website
2. Write the image to the SD card
3. Enable the SSH server by adding an empty file called ssh (no extension) to the /boot (small) partition on the SD card
4. Insert the SD card, connect the Pi to your router/switch and power the Pi up
5. Connect to the Pi - the name of the computer will be raspberrypi with a username of pi and password of raspberry

Raspberry Pi configuration

Configure the following using sudo rasbpi-config

1. Under System Options, connect to your Wireless LAN, change the password and change the Hostname to something other than raspberrypi.
2. Under Performance Options, reduce the GPU Memory to the minimum (16MB) as it'll be headless.
3. Under Localisation Options, set your Timezone and Keyboard.
4. If you plan on adding a display to the GPIO header, eable SPI and I2C under Interface Options.
5. Finish and reboot

If you don't want to use the user pi, then you should add yourself to all the groups that the pi user is a member of:

sudo usermod -a -G adm,dialout,cdrom,sudo,audio,video,plugdev,games,users,input,netdev,gpio,i2c,spi <username>

Install Packages

The GPSD server for Debian Buster is quite an old version which doesn't fully support u-blox. So the Backports needs to be added to the package sources:

echo "deb http://deb.debian.org/debian buster-backports main" | tee --append /etc/apt/sources.list
sudo apt-get update

If apt-get update returns an error saying "The following signatures couldn't be verified...", then you need to install each of the keys referenced:

Err:2 http://deb.debian.org/debian buster-backports InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 04EE7237B7D453EC NO_PUBKEY 648ACFD622F3D138

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 40976EAF437D05B5
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 648ACFD622F3D138

Update all packages, and then install all the required packages:

sudo apt-get dist-upgrade
sudo apt-get install dnsutils lsof screen vim tree telnet tcpdump git gfortran gpsd/buster-backports

Install Node.js 14

curl -fsSL https://deb.nodesource.com/setup_14.x | sudo -E bash -
sudo apt-get install nodejs

Configure GPSD

Devices gpsd should collect to at boot time.

They need to be read/writeable, either by user gpsd or the group dialout.

localhost:4000 provides the multiplexed GNSS serial stream

localhost:4001 provides the corrected rover stream

DEVICES="tcp://localhost:4000 tcp://localhost:4001"

Other options you want to pass to gpsd

GPSD_OPTIONS=""

Automatically hot add/remove USB GPS devices via gpsdctl

This is disabled so GPSD doesn't take control of the GNSS serial device

USBAUTO="false"

## Clone repositories
The [RTKLIB fork by rtklibexplorer](https://github.com/rtklibexplorer/RTKLIB) is optimised for *"single and dual frequency low cost GPS receivers, especially u-blox receivers"*, but has not Debian package, so will need to be cloned. This repro should also be cloned.
``` bash
mkdir -p ~/src
cd ~/src
git clone https://github.com/rtklibexplorer/RTKLIB
git clone https://github.com/oobayly/pi-rtk

Build and install RTKLIB

As of 21 April 2021 there's a bug in RTKLIB where the rtkrcv doesn't start if run with a telnet interface. This PR fixes the issue, so a patch needs to be applied.

cd ~/src/RTKLIB
patch -p0 < ~/src/pi-rtk/patches/rtklib-patch-38.diff
cd ~/src/RTKLIB/app/consapp/
make
sudo make install

Install pi-rtk package

The pi-rtk package install itself into /opt/pi-rtk, and will do the following:

• Install systemd service files
  • pi-rtk-multiplex - Allows multiple applications to read from a single GNSS serial port
  • pi-rtk-base - Operates the system as an RTK base station that can provide data to an NTRIP Caster
  • pi-rtk-rover - Operates the system as an RTK rover
  • pi-rtk-http - A HTTP server that allows a user to view the status of the station
• Install configuration files int /etc/pi-rtk
• Install cronjobs for the ubx/RINEX pi-rtk-multiplex service

The Nodejs HTTP server needs to be built before installation

cd ~/src/pi-rtk/
npm --prefix pi-rtk-http install
npm --prefix pi-rtk-http run build
sudo ./install.sh

Configuration