freerunner at newkirk.us
Fri Oct 10 06:55:06 CEST 2008
On Fri, 10 Oct 2008 01:01:14 +0100, Rui Miguel Silva Seabra <rms at 1407.org>
> Big question:
> Are the accelerometers constantly draining battery life?
> The rate at which they feed me data only starts up when the file
> handle is opened, and stops when it's closed?
> If it's the first case, then the init scripts should shut both
> accelerometers down as soon as possible, and software that uses them
> should turn them on as needed.
AFAIK by default they're always powered up. Certainly apart from the times
I hit 'dead accelerometers' that took a few reflashes to get going again,
I've never had to power them up unless I'd previously powered down.
According to the datasheet at http://wiki.openmoko.org/wiki/ST_LIS302DL:
Symbol Parameter Test conditions Min.Max.Unit
Idd Supply current T = 25°C, ODR=100Hz 0.3 0.4 mA
IddPdn Current consumption in T = 25°C 1 5 μA
So the power draw is pretty low, both together being less than one
I suspect that frameworkd will be able to shut them down automatically if
nothing needs them, once accel support is incorporated. (IIRC it does that
now for other subsystems, like gps)
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