[sdiy] Proposed DSP board

[Tim Ressel]

I have one of those on order, but it will not get here until April. I can't wait that long, so I started a quickie dsPIC design so I can get my DSP on.  I was hoping to make the board so that it will be useful for other things and to other people. That way it's not a throw-away board.

I think an interesting board would be a DSP stamp. Just a DSP and codec with a link to the processor of your choosing. 

--TimR


--- On Thu, 1/22/09, Robin Whittle <rw at firstpr.com.au> wrote:

> From: Robin Whittle <rw at firstpr.com.au>
> Subject: Re: [sdiy] Proposed DSP board
> To: "Synth DIY" <synth-diy at dropmix.xs4all.nl>
> Date: Thursday, January 22, 2009, 5:58 AM
> A quick look at the 24 bit Motorola board:
> 
> http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=SYMP_SOUNDBITE
> 
> for USD$150 looks hard to beat for power, ADC and DAC
> channels, etc.
> 
> (Just wait for the USD to devalue . . . but will it devalue
> faster
> than your own?  Every currency will be racing to devalue to
> prop up
> its local industry, and as a natural consequence of every
> government
> printing money for this purpose.)
> 
> My interest in dsPICs is in their cheap, 28 pin DIP, with
> dual audio
> DAC models.
> 
> If you want to go to surface mount, spend a lot of money,
> there are
> faster DSPs which handle more then 16 bits.  Doing quality
> audio in
> 16 bits is pretty tricky.
> 
> If you want to do 32 bit floating point audio, I guess
> there are
> bigger DSP demo boards - and also current PCs are damn-fast
> at this
> sort of thing, with Csound, assembly or I guess C.  Quite
> small
> PC-compatible boards are available with four-core CPU chips
> running
> at 3 or 4 GHz - for a few hundred dollars.  I guess that
> various ADCs
> and DACs can be plugged into them via PCI or USB.
> 
> But if you want a device for a few dollars which takes up a
> postage-stamp's worth of board space, and which can do
> prodigious
> work on 16 bit audio, and have 16 bit audio DACs on board,
> in a DIP
> package for convenience of servicing and small-scale
> production . . .
> I think certain dsPIC models are impossible to beat:
> 
>   dsPIC33FJ128GP802
> 
> http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=8183&mid=14&lang=en&pageId=75
> 
> I have some samples but have not yet tried programming
> them.
> 
> It takes some time to figure out the assembly language
> programming
> and IDE, but it is possible to do a huge amount of work
> with these
> things.  Sampling at 44.1 kHz, you have 907 instructions to
> play
> with.  A single instruction can multiply and accumulate,
> preparing
> operands ready for the next cycle.
> 
> I did some development work for a client using a 33MHz
> dsPIC30
> device, and found it very good.  The primary limitation is
> not having
> a lot of RAM for reverb and the like, unless perhaps going
> to a 100
> pin dsPIC and static RAM, which means higher costs, big SMD
> chips etc.
> 
> There are SPI RAM chips now - 256k bit from ON
> Semiconductor:
> 
>  
> http://www.onsemi.com/PowerSolutions/parametrics.do?id=2207
> 
> In principle, this could be used with a 28 pin DIP dsPIC,
> but when I
> looked at the programming briefly, I decided it would be a
> lot of
> mucking around and not very fast.
> 
>  - Robin
> 
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