Power Management on Neo1973

Nils Faerber nils.faerber at kernelconcepts.de
Fri Jan 11 11:34:27 CET 2008

Tim Niemeyer schrieb:
> Hallo Shawn,

> * Shawn Rutledge <shawn.t.rutledge at gmail.com> [10-01-08 14:19]:
>> Well what's the best uptime on battery that has been seen so far, with
>> unmodified phones and with an existing software image?  I see less
>> than 20 minutes when I'm trying to just use it as a GPS (logging track
>> points).  GSM talk time ought to even be longer than that, but this is
>> without being connected - just sitting there idle.  And as others have
>> observed, if it is in more of a standby state, you still get mere
>> hours at best, right?  5 days seems wildly optimistic to me, but if
>> it's achieved it would be better than the average "smart" phone (all
>> OS's included).
> with actual battery you need to minimize the power consumption to 10mA for 5h lifetime!
> When i was GPS logging for OSM (Navit with map input from it's own
> output, was very nice), neo runs easily several hours!

That seems realistic, yes.

> Today, i played a bit with power measurement and standby.
> It was very surprising, and the actual power was very different from time
> to time. Sometimes neo booted and did draw about 400mA in idle. Sometimes only
> 280mA.

Yes, the runtime power is comparable dramatic - and about 50% of it is
caused by the LCD backlight. When reducing backlight brightness this can
dramatcally be decreased.

> In Standby mode it was exacly the same, but most the time it tooks
> ~80-95mA. Sometimes only 65mA!
> One time the neo did draw only about 20mA! Don't know what was
> different: booted -> standby -> 20mA! I think this 20mA was drawn by the
> GSM.

Right. If all other devices are properly switched off, only CPU is in
standby and SDRAM is in self-refresh then the device should not draw
more than ~4mA. A constant drain of 18mA or more from the GSM really
kills the battery life - 20mA means roughly 60 hours of standby, which
is acceptable but still not good.

In standby really every single mA makes a huge difference...

> Tim Niemeyer
  nils faerber

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