Per instructions in the Oracle Embedded Java MOOC this week, here’s the steps to get gpsd setup to read from the sensor if it’s attached via a USB TTL cable:
sudo apt-get install gpsd gpsd-clients python-gps
ls /dev/ttyUSB* – to check what USB port we’re connected to
sudo gpsd /dev/ttyUSBx -F /var/run/gpsd.sock to start the daemon, replace x with the port number from step above
cgps -s – to run the client
If the GPS is attached via GPIO pins, then, similarly to above:
ls /dev/ttyAMA* – to check what AMA port we’re connected to
sudo gpsd /dev/ttyAMAx -F /var/run/gpsd.sock to start the daemon
Check check you’re reading data from the connected port, you can do:
cat /dev/ttyAMA0 – and you should see the raw messages being read from the card.
To interpret data coming from the card, read a line until you get a line prefixed with $, and then the next 5 chars represent the message type:
$GPGGA = gps position data
$GPVTG = velocity data