[sdiy] DSP synth applications (was DIY Polysynths)

[Tom Wiltshire]

If it helps, I second what Eric said.

Obviously different people have different wish-lists, but the SPI is  
a must. If you've got that, you can sort out the lack of ADC yourself.
Like Eric, I can see a lot of uses for a reasonably powerful 24-bit  
DSP which doesn't require a huge amount of support circuitry to get  
it running.

I've recently been looking at the Spin FV-1 and the Alesis/Wavefront  
AL3101/3102. Both of these chips have their uses, but neither of them  
can do what I'd like them to do. I suspect the Soundbite DSP 56371  
actually can, but it's a bit of a hurdle to find out for sure.

Thanks,
T.

On 29 Jul 2009, at 19:58, Eric Brombaugh wrote:
> Terry,
>
> First, thanks to you and your colleagues at Freescale for making  
> the SoundBite boards available. I picked one up early last year and  
> got as far as writing a few simple test apps. I worked a bit with  
> David DiCarlo on reviewing some of the documentation and debugging  
> some IDE conflicts with ARM/OCD tools installed under WinXP.
>
> The DSP56371 used on the Soundbite looks like a potentially useful  
> part for a number of synth applications I'm familiar with. That  
> said, the lack of standard interface peripherals is a significant  
> hurdle. Anyone wishing to do more than rudimentary digital bit- 
> banging for user-interfaces is probably going to have to add a  
> second, more general-purpose MCU to handle things like MIDI, CVs  
> and user interfaces. Not that this is an onerous problem, but it  
> does create barriers that will discourage a significant fraction of  
> the potential user base.
>
> Most of my audio DSP experience has been at the lower end of the  
> performance spectrum - things with 20-60 MIPS and 16-bit wordsizes.  
> I've become pretty familiar with the compromises that these  
> restrictions impose and I'd love to see some inexpensive parts that  
> are easy to use in a DIY context and provide more horsepower and  
> resolution. My wish list looks like this:
>
> * >= 24-bit words
> * >= 60MIPS
> * >= true DSP with MACs and multi-bus operand prefetches/addressing
> * fast vectored interrupts from on-chip sources
> * single-cycle (no wait) on-chip memory accesses (program & data)
> * >= 16kword on-chip data SRAM
> * >= 32kwords program flash (or SRAM auto-loaded )
> * At least one I2S-capable interface
> * SPI, both master and slave capable
> * UART
> * >= 8 GPIO
> * >= 3 32-bit timers
> * >= 4 channels 12-bit ADC
> * <= 144-pin TQFP (48, 64, 80 preferred)
> * < $10/ea in small qty from a common distributor
> * free / low-cost development tools
>
> It's a bit of a list, but several of the DSP56k parts already meet  
> many of the bullets. I believe that the biggest hole is with the  
> SPI master, UART and ADC (and the ADC would be less important with  
> several SPI master channels) - adding these capabilities would make  
> the 56k family quite attractive for my future projects.
>
> Eric