Robert Rolf wrote:
> Can't you tell that just from the value you set for the reference voltage?
> Seems to me 3 pins is all you need since the number of cells also determi=
nes
> the reference voltage you want.

The charger has a fixed reference voltage (2.048V -- a little close to the =

PIC's 2V minimum, but it seems to work).

One NiMH cell has a maximum safe voltage of 1.5V, but I'd like to give the =

circuitry the ability to measure up to 2V (just for the sake of having a bi=
t =

of a safety margin)

> Or something. 1% resistors attached to tri state pins on PIC to change
> values in binary. If you're clever about the R values you can probably
> get away with ONE pin. Low, Tristate, High for  1, 2, 4 cells.

Hm, not in an opamp feedback circuit. I could replace the pulldown resistor =

with a permanent pulldown and two switchable parallel resistors.. Good idea=
, =

thanks. 5p worth of resistors vs. a =A35 digital potentiometer IC...

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