JetsonHacks

Level Shifting, UART and GPS Part 3 – NVIDIA Jetson TK1

GPS through Jetson GPIO UART

Testing

With the wiring completed, we can try out our new GPS system.
Turn on the power and boot the Jetson. Once the Jetson is up and running, open a Terminal. Execute:

$ sudo cat /dev/TTHS1

You should see a stream of GPS information, which is in NMEA format. If not, you need to start trouble shooting. First make sure that you typed in the correct command. Next, it’s time to start checking the wiring. It doesn’t take much in the way of wiring error for things not to work. Check the connections. A good rule of thumb is to just connect it up right the first time so you don’t have to debug it. Just sayin’.

Software Installation

In order to use the GPS, we need to install some software:

$ sudo apt-get install gpsd gpsd-clients python-gps

which installs gpsd, a Linux daemon that interfaces with the GPS serial stream.
Once installed, we can turn on the gpsd daemon:

$ sudo gpsd /dev/ttyTHS1 -F /var/run/gpsd.sock

Once gpsd has been started, run:

$ xgps

After a while, the GPS will find the GPS satellites in your vicinity and triangulate your position. Xgps will show the satellites that it is using to calculate the position.

Note: It may take several minutes for the GPS to get a fix with the satellites. After the GPS synchs, the red light on the GPS board will flash about once every 15 seconds. If the GPS does not get a fix, it probably means that the signals from the satellites are not strong enough. The GPS device has an antenna built into it, but it may need an external antenna. The GPS board has a uFL connector, most external GPS antennas connect with SMA so you will need something like a SMA to uFL RF Adapter Cable

Conclusion

This is a very simple circuit to execute and have fun with, a good entry into breadboarding a prototype. It’s harder to describe than to actually build the circuit, it takes about 10 minutes all together to build the breadboard, wire it, and test it out. The project is actually useful after you have it finished, so it is definitely worth trying. Good luck!

Back to Part 2