On Wed, 20 Aug 2008 15:56:52 -0400, "Rodent of Unusual Size"
<RoUS@sourcery.org> said:

> I have three strings of LEDs whose brightnesses are to
> be controlled with PWM, and each string independently.
> The dual inputs are for 'increase brightness' and
> 'decrease brightness,' so it's a simple 1/0 input.

> > What frequency does the PWM need to be ?
> 
> Not critical, just above visual flicker rate and
> with a 0-100% adjustable duty cycle.

So you probably don't even need a hardware PWM peripheral, all three
channels could be done in a timer interrupt. If you set it for 20000
interrupts per second you could have a resolution of 1 percent and a
refresh rate of 200 Hz.

With modest cleverness you could probably do 10 times better than that
if you really needed to. 100 times better would require excessive
cleverness :)

So you could do all three channels plus six buttons on your 16F627A with
room to spare.

Cheerful regards,

Bob

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