It sure sounds as though you're controlling a servo  ;-)  I'm
using TMR1 to do this.  It generates the 17ms interupt.  On
interupt, it begins counting down a variable and setting the
output bits controlling four servos.  This takes 1ms.  Then it
sets up a 1 ms interupt and processes the main code loop in the
meantime.  After this 1ms delay, the servo control bits are set
low and TMR1 is set to generate an interupt in 17ms.

I know that this isn't what you want but I couldn't think of a
way to use the PWM generator that was any easier.  Let me know
if you'de like my code.

Andrew
akieran_at_ureach.com



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---- On    , Robert B. (piclist@NERDULATOR.NET) wrote:

> I need a PWM signal with the following specifications (from
the
> manufacturer):  period 17ms, minimum duty 1ms, maximum duty
2ms.
>
> I'm using a PIC16F873A on this project, and would really
really really like
> to generate the PWM in hardware.  Reading the chip's datasheet
implies that
> the slowest PWM signal on the CCP1/2 is 1.2kHz (about 20x too
fast).  Are
> there any clever tricks that can slow it down to about a 17ms
period?  All
> the timers and interrupts are free for use, but like I said if
there's a way
> to get the PWM module to do it that would be ideal.  If all
else fails I can
> cobble together an interrupt to do it, but the code is fairly
time critical
> so it would need to be really quick.
>
> Thanks!
>
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