That still limits me to a square wave though.
It would be nice to have some time for some d/a conversion that would lead to
a lower THD. (less parts, more complex software = cheaper and more fun for a
hobbyist)

Anybody built an d/a convertor out of the USART and and integrator before or
am I the first (I mean, with a PIC. I know SACD works roughly this way)?
The idea:
1 = curve goes up
0 = curve goes down
Tied to an integrator with virtual ground at Vdd/2 this would give the curve
back.
So a sine would look like 111011010101001000000100101010110111 and loop
(draw it if you don't see it)
As you can see this is quite small, and can be compressed much more: a sine is
pointsymmetrical(?) so you can mirror halfway, and invert a quarter.
So you only have to store a quarter of a period, one byte would lead to 32
samples/period. I haven't been able to calculate the harmonic distortion, but
its surely more smooth than a square wave :o)

But I guess I have to open up my filter design book... oh wait thats a next
quarter course... :o)

Greetings,

Koen

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads