Accelerometer question

Joel Newkirk freerunner at
Fri Oct 10 06:55:06 CEST 2008

On Fri, 10 Oct 2008 01:01:14 +0100, Rui Miguel Silva Seabra <rms at>
> Hi,
> Big question:
> 	Are the accelerometers constantly draining battery life?
> 	or...
> 	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

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
       power-down mode

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)


More information about the community mailing list