SV: Re: SV: Re: [sdiy] Two Nuts & Volts articles from last year

[Karl Ekdahl]

Everything i do is coming from the perspective "i have
a sh*tload of free time and *no* money wse". That's
why i used the r2r approach, so of course, you're
right about noise and perhaps also the PICs outputs
aren't really stable enough current sources to do this
but if you've got no alternative... I'm currently
expanding the module a *lot* but here's the original
circuit: 
http://www.sdiy.org/knas/modsynth/usb2cv.html

I don't know any better so i published the code based
on microchips original, i'll keep it online until
someone tells me to take it down... :)

Karl

--- Eric Brombaugh <ebrombaugh at earthlink.net> skrev:

> Karl Ekdahl wrote:
> > That might go for the midinator, but for just
> building
> > a simple usb->midi you just ask for a few free
> samples
> > from microchip and get going...
> >   
> True enough. It's hard to compete with free parts.
> > I have to say that this statement suprises me, i
> > haven't seen *any* usb->cv projects, that's why i
> > developed my own. And as far as usb->midi goes
> most of
> > them (inluding the MidiNator) are
> > "buy-this-i-won't-give-you-the-code"-stuff.
> >   
> You're right. I thought that I'd seen some but my
> brain was playing 
> tricks on me - it must have been wishful thinking. I
> also have noticed 
> the tendency to publish PIC USB projects but not
> supply source code. 
> Perhaps this is because many of them rely so heavily
> on the original 
> Microchip USB driver code which may not be licensed
> for redistribution.
> > personally i have "hängt flera stycken" of my
> design
> > in different "granar" that i have, and the current
> one
> > doesn't even use a d/a, just a r2r network and
> that
> > seems to work fine for the 5 octaves i'm doing.
> >   
> Your swedish idioms perplex me! :)
> 
> R/2R ladders are fine if your CMOS output stages can
> drive the current. 
> Note that they will be susceptible to any noise on
> the digital supply 
> rails, and any switching noise generated on-chip in
> the PIC processor. 
> You can eliminate that problem by running the R/2R
> network from a buffer 
> that's powered from a clean supply. A bit more
> complex but still 
> probably cheaper than a DAC (unless you got the DAC
> for free too!).
> 
> I'd be interested in your USB->CV project. Is it
> online somewhere?
> 
> Eric
> 
>