[sdiy] Sound synthesis with microcontrollers

[jbv]

Neil Johnson :

> Mmmmm... sounds like a DSP to me.  But with more soldering, and slower.

Mmmmh... probably slower than a high end DSP, but at 75 MHz
and with Logic Devices multiplier (15 to 20 ns AFAIR), quite a
few interesting things can be done...
As for soldering, I guess that some of you guys do that daily, but
I just can't imagine designing / soldering around a 240 pins MQFP...
And my core design shouldn't include more than 4 or 5 chips...
As for software, things like an osc with linear interpolation and expo
converter are just straightforward loops, not so difficult to code and
optimize in assembler...

> 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.

Geez ! that's at least 10 times what I expect my module to cost...

> 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
>

Looks interesting, but any idea how much this costs ?And one more question :
once I've written and debugged my code on
my eval. board, what if I want to cook my own little module to implement
it ? How do I switch from this board to my own circuitry ?

> > - 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.
>

Yes, that's probably true for research & prototyping...
But IMHO it actually depends on what I'm after...
For instance, if I want to implement a simple vco or vcf module,
the XA with its (rather) fast multiply-accumulate and
onboard ADCs / UART / RAM etc. can do the job easier & cheaper...

JB