[sdiy] Sound synthesis with microcontrollers

[Neil Johnson]

JB,

> Yep, I see your point. Actually the frontier between uC and DSP tends to
> blur, especially with the 16 bits uCs...

Especially when you consider also that the target applications are also
merging, with uC designers adding features to support DSP, and DSP
designers adding support for interfacing to devices _other_ than ADC/DACs.

> Please correct me if I'm wrong, but I still consider a 16 bits uC easier
> to implement for a DIYer than a DSP...

Texas Instruments do lots of eval boards with free assemblers and stuff.
One of my students bought a TI DSP board that had a rather nippy 16-bit
fixed point processor, stereo audio in/out, expansion port, came with a
full C compiler + IDE, libraries, etc, all for about 295 UK pounds.

> I found countless eval. boards and free prog. tools for uCs in
> magazines, but very few for DSP...

The ADSP2181 is a popular 16-bit DSP, quite cheap too, and has 48k of RAM
onboard.  Here's an example system:

	http://www.sowa.synth.net/evm2181.html

Hmmm...that name looks familiar.... ;-)

> Besides, when you check app notes for uCs, you can find many signal
> processing algos (FIR filters, FFT...) easy to implement...

Have you bothered doing a google for DSP app.notes?  Far too many to list,
not to mention all the support materials that companies like TI produce
for teaching DSP stuff to undergrads, which is free to anyone who asks.

> I have the feeling that DSP tends to be used mostly for high end complex
> apps these days...

Like a fax machine?  ADSP2181 again.

> And of course, cost is an important decision factor for DIYers. For
> instance, in Farnell catalog :

> - Philips XA-S3  68 pins / 16 bits / 30 MHz : 25 euros
> - Sharc DSP   240 pins / 32 bits / 50 Mips / 40 MHz : 74 euros

My guess is you'd maybe get 10MIPS out of the XA?  Whereas the SHARC
(which is a high-end 32-bit floating-point DSP) is giving you a full
50MIPS.  So really, bang-for-buck, its quite good value.

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
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