How to generate two PWM from PIC18F452

Johnson Kao · Guest

Dear All,
I will generate two PWM from PIC18F452. The two signal will be push-pull within a deadtime. Have anyone know how to do? I have tried many times but all failed. Have any sample code for reference? Thanks a lot,

Johnson

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

This post shows how to do simple dual PWM using the CCP modules.
http://www.ccsinfo.com/forum/viewtopic.php?t=17729&start=1
However, that's not what you want to do.

John P · Joined: 17 Sep 2003 Posts: 331

It all depends on the frequency of the waves you want to generate, and the resolution of the PWM outputs. It could be an easy project, or just plain impossible. You'll have to explain more.

Guest · Posted: Mon Dec 24, 2007 10:04 am

John P · Joined: 17 Sep 2003 Posts: 331

Maybe I wasn't clear about what's needed to understand the requirements. By "resolution" I meant how many different pulse widths need to be produced, potentially.

For instance, you're saying that the period of the output signal, at 50KHz, must be 20usec. So would it be acceptable to have the ability to produce 11 different outputs, at 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, or 20 usec (where 0 and 20 would be "always off" or "always on")? I'd call that "10% resolution"; if it's not acceptable, what would you need?

Also, will the chip have to do anything else while this runs, such as servicing interrupts? Communication of any kind?

I'm thinking that there might be a minimal way to do this, by setting up a loop outside of any interrupts which simply decrements a counter and flips external port pins at the right times. But it won't be able to keep doing that and service interrupts or do much of anything else at the same time unless you can tolerate disruptions in the output waveform.

And if a change in duty cycle is called for, is irregularity in the waveform acceptable for one (or a few) cycles a during the transition?

Johnson Kao · Guest

Resolution is 40%.
Thanks a lot,

John P · Joined: 17 Sep 2003 Posts: 331

You're not providing enough information to know if this can be done or not.

Also, is it a class project? If so, I think you need to figure it out for yourself.

Guest · Posted: Fri Jan 18, 2008 2:46 pm

for example?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

There are many projects posted on the internet, that show how to use
a PIC to drive a motor. Do a search with http://www.google.com for