GPS stopped working, can't figure it out... what else?

Al Johnson openmoko at mazikeen.demon.co.uk
Sat Jul 10 21:03:08 CEST 2010


On Saturday 10 July 2010, Yaroslav Halchenko wrote:
> thanks everyone -- I will check it out although I am a bit confused
> since
> * originally GPS worked for me without AGPS at all, just TTFF was around
>   2 min

It still should work. TTFF will be ~40s in ideal conditions, longer as 

> * I thought AGPS feeding chip with previous locations was already
>   implemented and that is why there is a button to remove AGPS data
>   if you rellocate (used it few times, and then again acquired time/fix
>   within few minutes)

It is, but I think there are deficiencies in the implementation. It seems to 
save incorrect data in some situations (like shutting down gps before it has a 
fix), then load it next time the GPS is started. Depending on how lucky you 
are it can then take a long time to get a fix, or not get one at all. In this 
case shut down the gps, remove the stored data, then start the gps again.

> now I am experiencing now fixation (or even time acquisition) at all,
> which sounds somewhat different... but ok -- I guess I better check
> first what effect I would get with "online assistance".
> 
> On Sat, 10 Jul 2010, Ian Darwin wrote:
> > > I got me a password from u-blox.com and use the script from this page:
> > > http://wiki.openmoko.org/wiki/Neo_FreeRunner_GPS#GTA02_GPS_Hardware_Ass
> > > ist_Feature (the python one). I set the values for lat and lon to known
> > > values (for me lat=52.375756;lon=13.651114;) and feed the output into
> > > /dev/ttySAC1 -  this speeds up finding satellites alot.
> > 
> > This is an important action if you're using the GPS. The wiki discussion
> > cited above could use
> > some cleanup but the information you need is there. Anyone using a FR
> > device and wanting
> > to use the GPS should be using this. There's even a version for Android
> > On OM at
> > http://androidgps.blogspot.com/2009/02/priming-openmoko-u-blox-gps-chip.h
> > tml




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