> I need a simple squarewave generator with a range of
> 0 Hz to ~5kHz.  I tried breadboarding a simple 555
> circuit, but it's horrendously unstable
> (the freq-counter is not thr problem).

If you only want a square wave then a simple low cost crystal controlled
function generator is only a PIC away. 5 kHz gives you 1/5000/2 s = 100 uS
per half cycle giving oodles of time to read control buttons between
toggling a port pin.

You could do this with a timer and interrupt or a timer and loop. Key trick
(not a hard one in this application) is to maintain all paths of constant
time period (isochronous) so you don't get jitter when a key is pressed or
released.


        RM

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