>   2) Check your MOSFET driver carefully - look at each bit separately and
> figure out what's going to happen when it gets a high input, then do the
> same
> for a low input.


Also when the proc is in reset, or being programmed!


I managed to build a driver that switched on when Vin was
> low. The PIC realised Vout was going way too high, reduced the PWM time to
> zero, and ended up locking the MOSFET on instead. Oops. At least it didn't
> let
> out the magic smoke, but it did burn the solder flux residue a little...


Ain't it fun? :)

  3) Hooking up power to the opamp is a very good idea too. I spent 40
> minutes trying to figure out why Vout was stuck at 0V, then noticed the
> opamp
> was plugged into the "V4" bus line, and that there was no link between
> "V3"
> (SMPS supply voltage) and "V4"...
>   4) Cheap breadboards are very good at developing loose connections.


Definitely. I'd proto the power part on some PCB material, and fly-wire it.

  5) I need to get some decent single- and double-cell battery holders.


Tough. Especially with 1C sorts of charge rates.

What fun!
>
> I'm going to hook up a 20MHz crystal in a bit and see if I can get it to
> update a bit faster. I might also try rewriting the code to do PSM instead
> of
> PWM and see if that makes it work any better.


PSM?  As in pulse skipping?

Beware of the bifurcation.


And I need to try and figure out what part of the SMPS driver is eating
> nearly
> 200mA, even when the PWM output is off (=0V)...


Hmm.. That's not right.
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist