How to use 8 Mhz clock to generate slow PWM Frequencies

Brian · Joined: 29 Jun 2010 Posts: 10

Hi,

I am using the PIC18F2480 and one of the goals of my project is to output PWM signals with slow frequencies (between 10 - 100 Hz). I know how to accomplish this through setting the internal oscillator frequency much lower (125Khz or 250Khz); however, I would like to be able to use the normal 8 Mhz clock frequency or somewhere in the Mhz range.

Would it be possible to hook up a slow external crystal or oscillator for the timer to use to generate the PWM signals, but to run the main program from the internal 8 Mhz clock? Or are there any other ways to accomplish this?

Thanks.

Here's some sample code I'm using to generate, if it helps:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Look at the software PWM routines in this thread, using #int_rtcc (Timer0):
http://www.ccsinfo.com/forum/viewtopic.php?t=37807

Brian · Joined: 29 Jun 2010 Posts: 10

Thanks very much. I posted an additional question on one of the threads already created here:

http://www.ccsinfo.com/forum/viewtopic.php?p=137266#137266

Thanks.