Auto backlight management?

C. Scott Ananian cscott at
Fri Apr 25 11:46:37 EDT 2008

>> On Apr 24, 2008, at 10:39 PM, Frank Ch. Eigler wrote:
>>> Opportunistic use of the on-board camera and the time-of-day clock
>>> could yield such heuristics.

Just for reference, in my mind the best mechanism to do this on the
current hardware would have been to use the battery-status LED "in
reverse" to detect ambient light level:  Unfortunately, all the
display LEDs on our current hardware are behind drive transistors that
make this impractical.  For Gen 2, a simple photocell (or LED wired as
such) would be sufficient to provide proper backlight power management
while preserving privacy.

I have discussed with Chris implementing a hackish "low-power mode" to
demonstrate optimal power management on the Gen 1 hardware to
illustrate the potential of the XO.  Until software catches up, this
would disable USB (hence wireless) and SD to allow sub-200ms resume;
it might be interesting to make this manually-selected mode also do
the camera-as-light-sensor trick to properly manage backlight
intensity.  The goal of this would be to show what battery life is
possible; we could also enable/disable the backlight management
separately to justify (or not) inclusion of a light sensor in Gen 2

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