GPS Location Logger Sample

The GPS Location Logger sample works with any serial port (UART) based GPS sensor or with the Xsens GPS device connected over USB. The logger requires the GPS sensor connected over serial port to deliver messages in NMEA format, while the Xsens device connected over USB can run in proprietary mode.

Testing

Test the applications using consumer grade off-the-shelve GPS sensors, also known as GPS mouse (e.g., Garmin GPS).

Usually, these mice are connected over USB and implement a serial-to-USB connection with the help of FTDI devices. On Linux, these sensors can then be reached over the /dev/ttyUSB or /dev/ttyACM devices.

The sample requires the name of the tty device of the GPS sensor, for example:

./sample_gps_logger --driver=gps.uart --params=device=/dev/ttyACM0

Any valid GPS message that is received results in an output on the console similar to:

GPS[0] - 2671445399 lat: 37.3901 lon: -122.163 alt: 71.2 speed: 17.131 course: 190.6

Where the first number indicates the timestamp of the received GPS message in microseconds and the rest of the line indicates the geographical location of the sensor.

If no parameters are provided, the sample starts a virtual GPS sensor and interprets the content from the file located at data/samples/sensors/gps/1.gps as GPS input.

Baudrate

Per default, if no baud parameter has been provided gps.uart driver assumes a baudrate of 9600. In order to change the baudrate provide baud argument as:

./sample_gps_logger --driver=gps.uart --params=device=/dev/ttyACM0,baud=115200

Xsens GPS[/IMU]

The sample support reading GPS packets from a Xsens device through the gps.xsens driver. The driver expects Xsens device to deliver packets in Xsens proprietary format. To run the sample using Xsens device use:

./sample_gps_logger --driver=gps.xsens --params=device=0,frequency=100

Where device=0 parameter sets the index of the Xsens device (usually 0 if only one device is installed) and frequency=100 sets the frequency in [Hz] this device should operate with. Please note that even if the Xsens device is a shared device, like Xsens MTi-G-700, capable of delivering GPS and IMU packets, only the GPS packets will be parsed by the gps.xsens driver.

Sensor sharing

The sample also demonstrates how sensor sharing can be implemented. Two DriveWorks GPS sensors are created from the same hardware device. Both sensor can be then treated independently. Both sensors would deliver exactly the same set of packets. Each sensor is using, however, their own FIFO hence they can be drained at different rates. The output of both sensors is printed to the console:

GPS[0] - 2671445399 lat: 37.3901 lon: -122.163 alt: 71.2 speed: 17.131 course: 190.6
GPS[1] - 2671445399 lat: 37.3901 lon: -122.163 alt: 71.2 speed: 17.131 course: 190.6

The index [0], [1] indicates what sensor produced the output. As expected the data packets and their timestamps are equal.