G'day Kevin I was responsible for the idea to use an LED as a cheap light sensor on the XO-1.75, built the first prototype, and have been following the feature since.
To use an LED as a light sensor requires a special connection method; either the LED must be mounted in reverse, or both terminals of the LED must be directly connected to software driven input/output pins on a microcontroller or CPU. Mounting the LED in reverse prevents it from being used as an indicator. Using two software driven pins is an additional cost if there is a limit on the number of pins available. The embedded controller has a limit on the current it can supply to LEDs. None of the LEDs on XO-1 or XO-1.5 are connected in a way that supports their use as a light sensor. All of the LEDs on XO-1 or XO-1.5 are connected to driving transistors or MOSFETs. This is so that two LEDs, front and back of the hinged section, can be driven at the same time, with a tiny current draw from the embedded controller. But driving these LEDs in this way also effectively prevents their use as light sensors. I suggest that if you want to experiment with using LEDs as light sensors, that you get yourself an Arduino or similar, and play with that. It is much easier than opening an XO and changing the wiring. ;-) -- James Cameron http://quozl.linux.org.au/ _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
