PWM QUESTION

Guest · Posted: Sun Mar 05, 2006 4:53 pm

Hi,

How can i get continuous 455 KHZ of PWM with a PIC16F628A?
Could anyone post a piece of sample code about it?

Thank you.

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Take a look at the example EX_PWM.C that comes with the compiler.
<program files>\picc\examples\EX_PWM.C

Guest · Posted: Sun Mar 05, 2006 5:31 pm

Thank kender,

I was looking that, but i need to get closer values. For example.

1/20000000*4*1*11 = 454,545 hz and with 10 instead of 11 ->
1/20000000*4*1*10 = 500,000 hz

and I need 455khz. any suggestions?-

Thanks again.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

You may have to change your crystal frequency.
Look at the formula given in this thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=17993

Look at a catalog of crystals to choose a suitable frequency.
http://dkc3.digikey.com/PDF/T061/0916.pdf
(For a PIC, you want the non-series type. Pick the type that
has a load capacitance of typically 18pf or 20pf).