Getting GPS console output with gllin
This article describes the "quick start" procedure allowing to see the first output and actually use the GPS device in the command line mode, using the gllin driver.
After you download, scp and install the gllin_1.0+r350-r0_fic-gta01.ipk (or similar), it creates the folder 'gllin' in the root home. This folder contains the executable with the same name which starts the driver.
To get the output of this driver, read the file /tmp/nmeaNP (it is actually a pipe, not a file). The simplest way is to open another ssh connection to the phone and use cat:
Type cat after you start the gllin, not before. The output from the GPS driver looks like
$GPRMC,235946.99,V,,,,,,,120180,,,N*78 $GPGSA,A,1,,,,,,,,,,,,,11.2,5.0,10.0*36 $GPGGA,235946.99,,,,,00,00,5.0,,M,0.0001999,M,0.0020199,*57 (and so on).
The data are presented in NMEA format which gives a lot of data. The coordinates themselves are reported with the two messages that are described below.
GPRMC tels the latitude, longitude, speed, time and date. Hence the proper signal could also be used to set up the clock. If the device can see the satellites, the message looks like
- 143812 Fix taken at 14:38:12 UTC
- A A for the normal (active) message or V for the void message. Void messages are described below.
- 4301.028,N Latitude 43 deg 01.028' N
- 01232.000,E Longitude 12 deg 32.000' E
- 020.0 Speed over the ground in knots
- 083.4 Track angle in degrees True
- 240307 Date - 24rd of March 2007
- 003.2,W Magnetic variation
- *6A The checksum, begins with *
If the device cannot see the satellites properly (it usually does not work indoors unless very close to the window), it puts 'V' (void) at the output. In this case the GPRMC messages look like
In this case it is necessary to go to the more open place. It may take several minutes before device reports the correct location.