Getting GPS to work on Raspberry Pi 2 Model B
Enable the UART
By default the UART is enabled to allow you to connect a terminal window and login, We needed to disable this to free it up for the GPS Module. Edit the boot options to change the UART so it doesnt provide a terminal connection by default:
sudo nano /boot/cmdline.txt
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
Change inittab so it doesnt spawn a login to the serial connection:
sudo nano /etc/inittab
#Spawn a getty on Raspberry Pi serial line T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100
#Spawn a getty on Raspberry Pi serial line #T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100
If you just want to do a quick check to see what data is coming out of the GPS, you can enter the following command, following by CTRL+C to quit:
sudo cat /dev/ttyAMA0
Run the following two commands to stop and disable the tty service:
sudo systemctl stop serial-getty@ttyAMA0.service sudo systemctl disable serial-getty@ttyAMA0.service
sudo shutdown -r now
You can always just read that raw data, but its much nicer if you can have some Linux software prettify it. We'll try out gpsd which is a GPS-handling Daemon (background-helper)
To install gpsd, make sure your Pi has an Internet connection and run the following commands from the console:
sudo apt-get install gpsd gpsd-clients python-gps
Raspbian Jessie systemd service fix
Note if you're using the Raspbian Jessie or later release you'll need to disable a systemd service that gpsd installs. This service has systemd listen on a local socket and run gpsd when clients connect to it, however it will also interfere with other gpsd instances that are manually run (like in this guide). You will need to disable the gpsd systemd service by running the following commands:
sudo systemctl stop gpsd.socket sudo systemctl disable gpsd.socket
Should you ever want to enable the default gpsd systemd service you can run these commands to restore it (but remember the rest of the steps in this guide won't work!):
sudo systemctl enable gpsd.socket sudo systemctl start gpsd.socket
After disabling the gpsd systemd service above you're ready to try running gpsd manually.
GPSD needs to be started up, using the following command:
sudo gpsd /dev/ttyAMA0 -F /var/run/gpsd.sock
Now GPS doesn’t work indoors – as it needs a clear view of the sky so for this I’ve placed the PI on the window sill. Next I ssh into the pi and run cgps. There is a simple GPS client which you can run to test everything is working:
The -s flag is there to tell the command not to write raw data to the screen as well as the processed data.
It may take a few seconds for data to come through, but you should see a screen like this:
If you have any problems and cgps always displays 'NO FIX' under status and then aborts after a few seconds, you may need to restart the gpsd service. You can do that via the following commands:
sudo killall gpsd sudo gpsd /dev/ttyAMA0 -F /var/run/gpsd.sock
If here still shows 'GPS timeout' or 'NO FIX',edit /etc/default/gpsd as below:
sudo nano /etc/default/gpsd
change it to look like this
START_DAEMON="true" GPSD_OPTIONS="/dev/ttyAMA0" DEVICES="" USBAUTO="true" GPSD_SOCKET="/var/run/gpsd.sock"
then reboot. CGPS should work then.
NOTE:If the GPS receiver is new, or has not been used for some time, it may need a few minutes or so to receive a current almanac.You need 3 GPS satellites for a 2D fix (i.e. no height) or 4 satellites for a 3D fix. Once fixed,the LED '3D_FIX' will blink.
You can view http://www.catb.org/gpsd/ to get more info about gpsd.You can also try to use the following command:
cgps and gpspipe should both just show curated data in the same way as your cat command did.
Try running gpsmon to get a live-streaming update of GPS data!
The gpsmon real-time packet monitor and diagnostic tool. (This replaces the sirfmon tool in older versions.)