GPS testing on 2008.12

Jan Henkins jan at
Sun Dec 28 02:13:06 CET 2008

Hello Ed,

Thanks for the following:

Ed Kapitein wrote:
> Hi Jan,
> You could try to work on the low level first:
> If you activated gps in the settings, try to do
> cat /dev/ttySAC1
> this should give you some output like this:
> root at freerunner:~# cat /dev/ttySAC1
> NMEA unknown msg*58
> $GPTXT,01,01,01,NMEA unknown msg*58
> $GPTXT$GPRMC,,V,,,,,,,,,,N*53
> this would indicate that the unit is in fact powered on and working.
> Next you could try to start gpsd ( /etc/init.d/gpsd start )
> make sure the device in /etc/default/gpsd is /dev/ttySAC1
> now you can use gpspipe -r to check if gpsd is getting data.
> (gpspipe is in the gps-utils package, so you might have to use opkg
> install gps-utils first)
> it should look something like this:
> root at freerunner:~# gpspipe -r
> GPSD,R=1
> $GPZDA,,,,,00,00*48
> $GPTXT,01,01,01,PSRF inv format*2B
> $GPTXT,01,01,01,PGRM inv format*34
> $GPTXT,01,01,01,PFEC inv format*2C
> $GPRMC,,V,,,,,,,,,,N*53
> $GPVTG,,,,,,,,,N*30
> $GPGGA,,,,,,0,00,99.99,,,,,,*48
> $GPGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99*30

It turned out not to be neccessary, although I made a big fat note in my 
troubleshooting notes on the usage of gpspipe. In my particular case it 
turned out to be a twofold problem:

(1) My frameworkd was monitoring /dev/ttySAC1 in the ogpsd area of it's 
config, which interfered. I changed it to /dev/null, and it helped a lot.
(2) With the above, I braved the cold and went outside at about 1am in 
the morning, and got a fix after less than 20 seconds. Once I had a fix, 
the GPS kept it's lock.

Thanks for the tips!

Jan Henkins

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