On Tue, Apr 28, 2009 at 8:51 PM, John Watlington <w...@laptop.org> wrote:
> All of our LEDs are dual (one on the inside and one on the outside).
> Instead of running these in parallel, and throwing away the extra
> voltage, I run them in series directly from the battery voltage
> (ever notice that their brightness changes when you plug in
> the charger ?)

Is this a change to the Gen 1 design?  I remember studying the Gen 1
schematic and convincing myself it could be done if only we could run
an additional wire to an input pin.  You don't have to drive the LED
directly from the microcontroller; you only need to be able to switch
it and sense the voltage while watching the time.  The photocurrent
causes the inherent capacitance to discharge faster (or slower?  I
forget).  The time scale is really short, but that's no problem for
today's chips.  You could parallel a (very small) capacitor across the
LED to "make it more sensitive".

Any of the four existing LEDs would be appropriate: wireless "A" and
"B", battery, or power.  Heck, the two separate wireless LEDs cause
more confusion then they're worth anyway, you might as well get rid of
one and use the LED there only for input...

                         ( http://cscott.net/ )
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