smoother pwm control

cerr · Joined: 10 Feb 2011 Posts: 241 Location: Vancouver, BC

Hi There,

I'm looking for a way (if possible) to adjust the duty cycle for my pwm in a finer interval than 1%.
I'm running the pwm on a PIC16F883 with a 20MHz crystal. My timer2 (for the pwm) is configured like this

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

This thread has an example of using the CCP in Compare mode to
do PWM with finer resolution:
http://www.ccsinfo.com/forum/viewtopic.php?t=44328

Ttelmah · Joined: 11 Mar 2010 Posts: 19538

But, not at this high speed. :(
PCM's solution gives more steps for a low frequency PWM, but doesn't help at 200KHz.
At 200KHz, you are going to have problems. You can get a little finer, by going to a CPU supporting 25MHz, or switching to a 18 chip with a PLL, and going to 40, or possibly even 64MHz (depending on the chip). However the big question is do you really need 200KHz?.
The step size, is cycles on the clock, so if you could go down to 100KHz, and 40Mhz, you would have 400steps available, against your current 100.

Best Wishes

Mike Walne · Joined: 19 Feb 2004 Posts: 1785 Location: Boston Spa UK

Answer the questions.

Why do you need better than 1% setting?
Why do you need 200kHz?
What you are trying to achieve?

Then we may be able to suggest sensible solutions.

Mike

P.S. 1% setting gives a max 0.5% error