> Tony, you might take a look at the ckt Wouter used on his WISP
> - [I forget his URL]. I would imagine a variation on that could
> get you 3 different voltage levels for Vcc [eg, 4.5, 5, 5.5v]
> using only a single I/O pin, at 0, hiZ, and 1.

http://www.xs4all.nl/~wf/wouter/pic/wisp

beware: the calculation from the voltages you want to the resistors needed
is very difficult. In the end I gave up and the programmer simply generates
enough different voltages, more or less random divided over the interesting
range, and it must be calibrated to know which ones to choose.

Wouter

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