For an open house/demo for our new Pick and Place, we're using up some=20
PIC18f26J11's and PIC18f26K22's, both in the (same) wrong package, to=20
make a pair of 'digital dice'.  Basically 14 LED's arranged into the=20
pattern of two dice, appropriate current limiting resistors, attached to=20
high-current output PIC pins, and a pair of AA's to power the whole=20
thing, along with a pushbutton hooked to MCLR to re-roll the dice.

Simple algorithm:  Wake up, generate a random number, display on dice=20
(probably with some simulated rolling), and then wait 30 or so seconds,=20
then drop into SLEEP mode, or deep sleep if supported on that processor.

Problem being:   I really want to use MCLR to reset this so I can use=20
deep sleep.   AND... because I'm starting from the same state every time=20
the unit wakes up, I need an entropy source to seed a random number=20
generator.

My initial thought is to just sample the LSB of a hundred or so ADC=20
conversions from an unconnected ADC input, or maybe count the clock=20
ticks in a few cycles of the internal 32K RC oscillator.   or something=20
like that.   All seem workable, and I'll try a few of them... but was=20
also hopeful that someone on the list had had to do something similar=20
and knew what would or wouldn't work so I didn't have to reinvent the=20
wheel in this case.

Mainly I need enough bits to get a reasonably random distribution for a=20
number between 1 and 32 (I.E I need 5 'good' random bits, which are=20
fairly random.   Of course, more is better).

-forrest
--=20
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