[sdiy] Using an AT90S1200 as a triple DCO

[Tom Arnold]

On Mon, Feb 14, 2005 at 09:48:29AM -0000, Paul Maddox wrote:
> > I've updated my homepage (www.Jarek.synth.net).
> > You'll find there the schematics and the source code of my
> > voice board where an AT90S1200 generates 3 sawtooth waves.
> 
> nice, I'm fascinated why you chose to have the micro generate square waves
> rather than using a comparator on the sawtooth. was it to save on the part
> count?

Although I know he answered and said it was comparator based, I am curious
about something.  I've done DCO's with squarewave out simply because I could
not get a sawtooth->comparator to have a level amplitude across its entire
range so I had range issues at whichever end of the scale I couldnt tune
for.

I have gotten 8 squares out of an SX52 though... so thats what I played with.

I know the Juno's had the same sort of amplitude issue but I assume its
somehow compensated for.  Is there a standard-ish way of compensating?

I think the only reason I'd switch is because I have limited high-end with
the current setup.  Currently it tops out around 40k per voice and I'd like 
about triple that, which I could easily do by simply dropping all the extra 
code I wrote.  Although I should be able to get to 60k if I can get a 75MHz
resonator which I just havent bothered to do.  ( 80 if I can get the 100MHz
version of the chip )

-- 
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 - Tom Arnold       -  Free Synth DIY webspace http://www.sdiy.org 
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