Light sensor on XO-1.75

James Cameron quozl at
Mon Aug 29 17:51:43 EDT 2011

Please review

On Mon, Aug 29, 2011 at 07:06:32PM +0200, Bert Freudenberg wrote:
> And the blink rate is proportional to the light sensed? Why?

The sensor is a reverse biased LED.  The LED is charged in reverse
polarity, which makes the junction behave like a capacitor.  The
discharge time is related to the amount of light falling on the LED.

> >      Add compass driver for LSM303DLH.
> >      xo_175_defconfig: Enable magnetometer/compass.
> >      olpc-xo-1-75.c: Add compass support
> Is the compass exposed, too?

Yes, but you probably don't have one, and probably won't see one because
the magnet on the left lower corner of the laptop is incompatible with
use of a compass.  It is a handy magnet for holding USB drives though.

> Is there a list of all the sensors and how to access them somewhere?

Not that I know of.  Good idea. should be our
list.  But we don't have a list of how to access the sensors.

Check out /dev/input/event* as well, some of them are interesting, like
headphone jack plug events.

James Cameron

More information about the Devel mailing list