Hello Everyone,


        I need to produce a variable PWM output based on a 8 bit hex number
that corresponds to the percentage duty cycle of the PWM.  My basic idea was
use the interupt on overflow feature of timer0.

        So the waveform would look like this:

                  --------------------
        |         |                   |
        |         |                   |
        ----------                    ---------------

          $FF-PWM      PWM

        The pseudo code would look something like this:

Interupt_Service_Routine

        If the output was low last time
                {
                set the output high
                set timer0 to $FF - PWM
                //Set Timer to Over Flow PWM latter
                }
        else
                {
                set the output low
                set timer0 to PWM
                //Set Timer to Over Flow $FF-PWM latter
                }

End_Service_Routine


        Ok, well that seems simple enough to implement to me but what I
would really like to do is try this with one of the cheaper noninterupt
based PICs.   The problem is that the PIC will also be doing serial comms so
it can't be totally tied up with making the PWM signal although there isn't
alot else going on.

        I would appreciate comment and suggestions on both the interupt and
noninterupt based methods.

Thanks Guys,

Ben


Ben Wirz                For Microchip PIC Products including the Simm Stick
                        development system and Easy PIC'n Book, as well
Wirz Electronics        as Motor Control, Polaroid Sonar Units, and more
ben@wirz.com            Hobbyist Robotic & Electronic Supplies, visit:
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