Hi Jan,

I have just been working on some code that uses a 50:1 clock to
cutoff ratio chip and I had to produce a 750Hz - 50000Hz clock to
give a cut-off frequency range of 15 - 1000Hz. Very similar to what
you want but without the divided by 50 output.

I looked at using the CCP module to produce the square wave, as
Robert Rolf suggested each CCP interrupt changes the polarity of
the next CCP event so the output pin toggles state each time. The
problem in my case was I had too much other stuff going on with
interrupts and it was going to get all messed up especially at the
higher frequencies. I suggest it is probably a very good method if
you have no other interrupts enabled. Oh for a multi level interrupts!

In the end I used the PWM mode to generate my square wave,
switching the prescaler between 1:1, 1:4 and 1:16 to get the best
resolution over the full range.

Anyway, once you have produced your 500 - 50,000Hz square
wave using the CCP, it should be pretty easy in the interrupt routine
to increment a variable and when it gets to 50 toggle the state of an
output. Hey presto a divided by 50 output.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/text: 025 334 069
eMail:  brent.brown@clear.net.nz

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