PIC Ramps

No, if you want to use the PWM function to control the output by hardware, then you must use the CCP1 or CCP2 pin that goes with that PWM unit. Of course you can always run a PWM in software and then you can use any general output pin you like. The disadvantage is that this takes up a lot of processor time, which you may not have to spare in your application.

I have a PWM application on a 12C671 that uses sofware and timers, but no PWM hardware. It was a real bugger to write. But now that it is written, it has been integrated into a standard product.

Robert Scott Ypsilanti, Michigan

Generating a PWM signal is easy.

Assume "P" is your desired output value, from 0 to 100%. Initialize S to 0.

At every 100 usec heartbeat do this:

if( (S += P) >= 100 ) { S -= 100; set_output() } else clear_output();

You can change P whenever you want to change the output value. To make a 1 second ramp, just increment/decrement P every 100 heartbeats. You don't even have to use a second timer.

As an optimization, you could use 128 or 256 instead of 100, and make use of assembly tricks to simplify things.