Accelerometer question

Alastair Johnson alastair at
Fri Oct 10 12:51:16 CEST 2008

Andy Green wrote:
> Hash: SHA1
> Rui Miguel Silva Seabra wrote:
>> 	The rate at which they feed me data only starts up when the file
>> 	handle is opened, and stops when it's closed?
> This is the case, the interrupts are quenched when no file handles are
> open on them.
>> I'm just wondering, because my 1 year old Nokia 2670 just lasted a whole
>> week in idle on an 700mAh battery, and OpenMoko lasts only about 8/9
>> hours in idle with a 1200mAh battery. It is nuts, we all know that, but
>> I'm more interested right now into extending battery life, as it is my
>> single greatest problem with OpenMoko right now.
> The issue is "what does idle mean".  Suspend for Freerunner should last
> a week.  Sitting there with CPU up even with backlight down is 60-90mA
> on battery, suspend is 5 - 10mA and that's why you get battery life
> reduced accordingly if you stay out of suspend.  That's a kernelspace
> issue on the one hand (suspend is not entirely reliable) but also a
> userspace issue (there have been bugs negotiating entry to suspend
> instead of sitting there with CPU up at 400MHz and backlight down).

'Should' being the operative word :-) In practice it is variable to say 
the least. Sometimes a full battery will last a whole night with charge 
to spare in the morning. Other times the battery is dead. This is with 
bluetooth and gps disabled, no wifi connection but with gsm enabled and 
sim present. Image type doesn't seem to make much difference.

With GSM disabled I suspect it would last more than a week based on my 
accidental test with 2007.2. I switched off the GSM since I didn't have 
a SIM in, left it on Friday evening and forgot about it. On Monday I 
expected to find it dead, but it resumed with IIRC >80% battery.

I suspect the 'bouncing gsm' has a lot to do with it. I intermittently 
see repeated reregistrations. If the phone is near the PC speakers I can 
hear them, suggesting they require more power than sitting idle. This 
would probably not to explain the whole of the difference though, so I 
wonder if it is causing things to wake up when they ought to be 
thoroughly asleep. Any ideas on how I can record the number of wakeups 
and how long it spends awake? I wish I had an ammeter that could be used 
for data logging!

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