> Usualy, the standard PWM module(s) are not particular good at
> generating a standard 1.5 +/- 0.5 ms servo signal. And in
> many cases you have not a single servo anyway.

I've got a side project (active control of a inherently unstable flying
wing) that drives 4 hobby servos directly from a 24HJ32GP302.  The dsPIC
class PWM modules have wide enough period counters that you can do 500us to
2.5ms every 20ms with sufficient resolution in fire and forget hardware.

With a PIC 18 or something I would look into multiplexing the output of a
single PWM module.  The important observation is that you can fit a number
of 1-2 ms pulses in the 20ms repetition period.  You do the pulse for each
channel successively.  The multiplexer can be as easy as a AND gate per
servo output.  Now the PWM hardware only needs a period a bit more than 2ms=
,
so you should have enough resolution for the varying pulse width.


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