Ambient light sensing via LED response

[Peter Robinson]

> we had a dedicated light sensor on the last product i worked on
> (which, in retrospect, given that it had 15 watts (!) of
> backlight seems like maybe the wrong place to have started trying
> to save power ;-).  i implemented a proof-of-concept algorithm
> for automatic control, but found it a little weird -- it always
> felt like there was something wrong with the backlight as it
> shifted up and down in brightness, even with a fair amount of
> averaging and/or delay.  plus we never resolved how it should
> interact with the actual brightness buttons.  after all, if you
> adjust manually, you're probably unhappy with the setting that
> was chosen automatically.  so should manual control abort any
> automatic algorithm?  or maybe the buttons should tune the
> algorithm?  how?

The ALS on the Dell Latitude notebooks have either an auto setting
(activated using FN + Left Arrow) and Brightness Up and Down (FN + Up
or Down). When you manually adjust the brightness it disables the ABL
until you re-enable it.

Peter