Gerhard Fiedler wrote:
> Actually, I never used any of the special trigger features. Anybody
> has? Or are they just too exotic?

Yes.  Certainly not.

There are generally two ways to do PIC 16 periodic A/D sampling when the
period needs to be controlled well.  One is to start a new conversion in a
timer interrupt, then use the A/D interrupt when the conversion is done.
The A/D interrupt routine selects the new channel, and the timer interrupt
comes long enough later to ensure sufficient acqusition time.  I think of
that as the normal case since it doesn't use any additional hardware
considering you probably have a timer 2 clock tick interrupt anyway.

The other way is to use the special event trigger of a CCP module.  This
starts the A/D conversion automatically so you only need a single interrupt
per A/D reading.  Usually CCP modules are too valuable to dedicate to this,
but sometimes you need either the higher speed or low jitter A/D sampling.
The A/D interrupt then doubles as the clock tick interrupt.

On some newer 18F parts, you can set a fixed acquisition time delay from
when the GO bit is set.  It does the acquisition first, then the conversion
automatically and you get a single event when it's done.  The 30F A/Ds are
even more flexible.


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