Using SW, PWMing any output pin is pretty easy if you
use a fairly low frequency.  I've done it using a 50
uS timer tick and 8 bits.  Its just a couple of
instructions per pin.  You can get by with a lot fewer
than 8 bits, though.  LEDs don't need that high a
frequency unless the LED is moving.  

Phil


--- Dave Turner <dave.w.turner@gmail.com> wrote:
> Hey,
> 
> Not entirely relevent, but I thought I'd piggyback
> on this post - 
> 
> I already have 8 LEDs attached to portb4:7 and
> porta0:3.  I was
> wondering if I can use the PWM to fade the LEDs
> without moving them to
> a different port.  I am using the PIC18F1320.  How
> many pins can it
> support PWM on?  Which pins?
> 
> On 5/16/05, Jan-Erik Soderholm
> <jan-erik.soderholm@telia.com> wrote:
> > Jan-Erik Soderholm wrote :
> > 
> > > Now, just made a few additinal test...
> > > If I added a (dummy) assignment to T2CON
> *before* the
> > > call to PWM_Init, the source built OK !!
> > >
> > > OK, fine. Now on to test this on real
> hardware... :-)
> > 
> > Back from the tests...
> > 
> > After a few minor changes to the PWM example code
> > in the 16F877a directory, I now have a LED fading
> up and
> > down nicely connected to a 12F683 using the
> hardware
> > CCP/PWM module and the PWM library in mikroPascal.
> > 
> > Hep !!
> > 
> > The code looks like this :
> > 
> > program lhsim_01;
> > 
> > var j : byte;
> > var i : byte;
> > 
> > begin
> >   j      := 1;                  //  initial value
> for j
> >   i      := 1;                  // initial value
> for i
> >   TRISIO := 0;                  // designate gpio
> pins as output
> >   PWM_Init(5000);               // initialize PWM
> module (5 KHz)
> >   PWM_start;                    // start PWM
> >   while true do                 // endless loop
> >     begin
> >       delay_ms(1);              // wait 1 ms
> >       j := j+i;                 // increment j
> >       PWM_change_duty(j);       // set new duty
> ratio (0=0%, 255=100%)
> >       if j = 200 then i := -1;  // switch to
> fading down
> >       if j = 1 then i := 1;     // switch to
> fading up
> >     end;
> > end.
> > 
> > 
> > Regards,
> > Jan-Erik.
> > 
> > --
> > http://www.piclist.com PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> 
> -- 
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> http://mailman.mit.edu/mailman/listinfo/piclist
> 


		
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