Simultaneous PWM periods - PIC

Discussion in 'Embedded Systems and Microcontrollers' started by Vaughanabe13, May 28, 2010.

  1. Vaughanabe13

    Thread Starter Active Member

    May 4, 2009
    I'm looking to see if this is possible, because I can't find [the right] info in the datasheets.

    What I need:
    -3 independent PWM outputs, each running simultaneously at a different frequency (each in the tens of kHz range, if it matters). Duty cycle not critical, 50/50 is fine.
    -Must be a Microchip PIC running on 5V, anything 18F-series or higher. And because of the 5V-tolerant requirement, I'm guessing this rules out most if not all 24F, dsPIC, PIC32, etc. I'm willing to redesign the power supply for a lower voltage part if absolutely necessary, however.

    I have looked at different 8, 16 and 32-bit uC's from Microchip and I found several that had multiple PWM outputs (motor-control drivers, etc.). However, it appears from reading the datasheets that you are only able to program one period for the entire module, but multiple duty cycles for the different outputs. I want it the other way around - multiple periods and all running at 50/50 duty cycle.

    Is this possible with any PIC micros? If not, I will have to use multiple timers and interrupts to generate the PWM frequencies manually, which is definitely doable. I just wanted to see if there was a dedicated PWM option first.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Are you really trying to do pulse width modulation? If you do not vary the pulse widths, then you are actually generating three different frequencies. Are they related in any way?

    Perhaps you can clarify the application.