> Hi, I need to implement 2 DAC with one PIC,
> preferably a 16F84, and I need reasonably
> fine resolution, at least 64 levels, pref
> 128.
>
> I have tried the PWM options, but I need more
> speed, like the ability to adjust from full
> to zero output 32,000 times/sec. Using 20MHz
> PIC and home made PWM I can't even come close.
>
> So, any suggestions on getting 2x analogue
> output from a small PIC at high speed??

The easy solution is to use a PIC with two PWM modules or use external D/As.
However, you might be able to do this if you're very careful.  With 20MHz
clock and 32,000 analog out updates per second, you have 156 instructions
per update.  Doing one PWM at this rate isn't too hard, especially if there
are no other interrupts.

Doing two is going to be tricky, because handling of one will result in
latency (and therefore wrong value) in the other.  You'd pretty much have to
dedicate the PIC to doing nothing else.  In that case you probably need
another PIC to do the stuff this PIC can't do, in which case it would be
cheaper and easier to just get a PIC with two PWM outputs in the first
place.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olin@embedinc.com, http://www.embedinc.com

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.