David VanHorn wrote:
>
> >
> >First, are you charging and discharging through
> >separate pins? They may have different properties.
>
> I am charging through the same pin, discharging through different pins, and
> measuring with two of three pins.
> In the AVR, I could measure through the same pin I'm discharging with, and
> then I could do all the measuring on one pin.
>
> >The PIC output low (current sink) saturation
> >voltage varies with current. By varying resistances
> >there is a variance in current and also discharge
> >curves. The output sat curves are in the datasheet.


David, at the risk of sounding like a "bucket engineer"
have you thought about just measuring your results and
then using a lookup table?? Problem solved, and the
real world approach also compensates for all the
other variables that affect it. :o)
-Roman

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