Hi David,
If all you need is overcurrent and don't need super precision, you can
monitor the voltage drop in your power transistors. The trick is to
ignore the voltage when the transistor is off. But if you are generating
the drive from software then that is easy too. I didn't use analog in,
just a regular IO port. Don't use pins that are schmitt triggers! Use
the ones with ttl levels.

I posted a project many years ago, it uses a 16F876 generating PWM from
the timer interrupt and doing cycle-by-cycle current limiting, maybe it
will give you some ideas:

http://bobblick.com/techref/projects/sv2hb/sv2hb.html

Sorry my website hasn't been updated in 15 years, but at least the pages
are still there :)

Bob

On Mon, Jun 22, 2015, at 06:19 AM, David C Brown wrote:
> I need an overcurrent detector for a small DC motor.  I thought of using
> low side sensing with the ADC of a PIC measuring the voltage across the
> sense resistor and then doing the integration and peak suppression in
> software.  I can tolerate half a volt or more voltage drop in normal
> operation.
>=20
> This seems to such an obvious idea that I am surprised that I can't find
> any reference to it in a search for "overcurrent detection using PIC". =20
> So
> is there some gotcha that I am too stupid to see?

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