Light sensor on XO-1.75

Paul Fox pgf at
Mon Aug 29 13:29:20 EDT 2011

bert wrote:
 > On 17.08.2011, at 17:24, Martin Langhoff wrote:
 > > Saadia Baloch (4):
 > >      Driver to read Outdoor Light Sensor from EC on OLPC.
 > So this is exposed at
 > 	/sys/devices/platform/olpc-ols.0/power_state
 > And it seems to sit "behind" the blinking left-most LED? And the blink rate is 
 > proportional to the light sensed? Why?

the light sensor needs to share one of the existing light pipes, since
changing the laptop tooling to add a new one would be very expensive. 

we're still experimenting, but currently the wlan led needs to be off
in order to get a valid reading from the sensor.  so the led is held
off while the sensor gets its reading, and the time the reading takes
changes with the amount of ambient light.

the flashing wlan led is annoying, and wasn't really part of the plan. 
we may move the OLS sensor to the second-from-left light pipe, since
that LED (which on XO-1 is network activity, and on XO-1.5 is supposed
to be disk activity but hasn't been implemented) is meant to flash
intermittently in any case.  periodically inhibiting an intermittent
LED should be less intrusive.

 > >      Add compass driver for LSM303DLH.
 > >      xo_175_defconfig: Enable magnetometer/compass.
 > >      olpc-xo-1-75.c: Add compass support
 > Is the compass exposed, too? Is there a list of all the sensors and how to 
 > access them somewhere?

no compass is installed on most boards.  (only one or two here in 


 > - Bert -
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 > Devel at

 paul fox, pgf at

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