[sdiy] Simple DSP as VCO substitute (was Re: CEM3340 reissue)

jays at aracnet.com jays at aracnet.com
Tue Jun 14 22:16:20 CEST 2016


I work in embedded land and working with MicroChip and ARM chips is no 
problem. If I were to do it I'd go with more processor and a real audio 
DAC. If I can make life easier for myself and save time by spending more 
money on the hardware I'll do it. I waste a lot of time at work because 
of hardware people picking the parts with no idea of what the software 
needs.

 From what I've seen from people doing digital oscillators using PWM and 
dsPICs the upper rates of the osc seem to be ~8K. Also I think a cheap 
audio DAC would out perform a 12 bit PWM DAC.

Can't remember which MicroChip part it was (PIC32, PIC24 or dsPIC) but 
at least one had issues with the DACs being noisy. Might check the 
errata for the chip before you use it. That's always a good thing to do 
with processors before you commit to a design anyway.

There is also a person in Sweden I think that is making a number of 
dsPIC oscillators that might be worth a look. Can't look at Muff's from 
work (so much in a name) to find the info.

Jay S.

On 2016-06-14 12:46, Pete Hartman wrote:
> On Tue, Jun 14, 2016 at 12:40 PM, Tom Wiltshire
> <tom at electricdruid.net> wrote:
> 
>> There are definitely limitations with the chip (only six 12-bit ADC
>> inputs when using the DAC, for example), and moving to a digital
>> chip implies doing certain things differently (you won't get
>> multiple waveform outputs in parallel, for instance).
> 
> From the chip itself, perhaps, but then I'd think you could use
> traditional waveshaping to get the other waveforms if they're wanted.
> 
> 
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