How to maximize GPS battery life ?

[Timo Juhani Lindfors]

Xavier Cremaschi <omega.xavier at gmail.com> writes:
> It seems that GPS chip is able to keep the fix while FR is suspended
> (/sys/devices/platform/gta02-pm-gps.0/keep_on_in_suspend), but I need
> the CPU to log data, don't I ?

The GSM chip has an ARM cpu. It is possible to run code on it and
modify it to buffer the data to its own memory so that you only need
to wake the main CPU once every 10 minutes or so.

> - launch fsoraw -r GPS tangogps and start logging

tangogps consumes cpu time uselessly. I just

echo '?WATCH={"class":"WATCH","enable":true,"json":false,"nmea":true,"raw":0,"scaled":false,"timing":false}' | nc localhost gpsd > $HOME/gps/`date -Iseconds`.dump

currently with gpsd.

> - let the FR disable display after 30s (problem : any touch on screen
> will keep it up)

I have been using

http://iki.fi/lindi/openmoko/touchscreen-lock.c

for a year or so. It locks the touchscreen so that X does not see any
events unless you swipe the screen slowly from top to bottom with your
finger.

> if I want to use my FR as a GPS track logger (for an OSM mapping party
> for example), what is the best way to save battery life ?

I carry a set of external usb batteries with me when mapping. See

http://wiki.openmoko.org/wiki/user:lindi

for more info.