[music-dsp] Re: floating-point PCI cards

Paul Maddox P.Maddox at signal.QinetiQ.com
Thu Oct 27 11:15:30 EDT 2005


Steve,

> I was looking at the Soundart Chameleon but it seems
> debugging DSP code on it is quite convoluted since the
> only communication you have with the DSP is the HIO8
> host port. So all your debug trace has to get
> funnelled through the ColdFire and you can't debug
> code that crashes the DSP bad enough that the host
> port stops working.

Dunno, I didn't have too many problems finding bugs in my code..

> And it's only got three knobs! How can you make a
> decent analog modelling synth with only three knobs! I
> suppose Paul Maddox will have a strong opinion on that
> though, on account of his awesome Monowave II skin.

thanks, FWIW, I think the Chameleon is a superb 'development' platform..
I don't beleive its a great 'end-user' product.

> And no digital audio I/O :-(

agreed, but they wanted to hit a very specific price, so somethings had to 
be sacrificed.

> On the other hand it has a great code base. I guess I
> don't need to tell you guys that, you probably wrote
> most of it ;-) And it "has the MIDI engine from the
> Atari ST" so it must be good!!

RTEMS rocks.

> But then again it costs 500 euros, think how much PC
> power I could buy with that, maybe I could just live
> with another 20 milliseconds of latency.

But then you're into OS land, and OS crashes/stability issues and driver 
issues..

> And, most
> relevant to this topic, the Chameleon isn't floating
> point: it's 24-bit fixed point. Great for audio but
> the original poster specifically wanted floating
> point. Decisions...

fixed point math isn't that hard, you just have to remember its fixed point 
when writing the code.

> As far as I see it, the main problem isn't making the
> hardware, it's getting your hands on a good
> development environment and debugger for free. As far
> as the SHARC is concerned, Analog Devices want you to
> fork over thousands of dollars for their VisualDSP
> toolset.

Thats the problem with the SHRAC stuff, cracking DSP, zero developers 
because the cost of the tool chain!

> I designed a small DSP unit for my work that uses an
> ADSP-2181 fixed point processor. It is standalone and
> talks to a PC through a 115200bps serial link. We
> refused to pay for VisualDSP so we wrote our own
> toolset that lets you upload and download to the DSP's
> onboard memory, burn the flash ROM, etc. We used the
> old command-line 2181 assembler that you can still get
> hold of, and ADI's free library routines.

neat.

> The 2181 is a pretty unimpressive chip- it's probably
> no faster than the ColdFire auxiliary CPU in the
> Chameleon- but it ended up doing all we wanted with
> power to spare. I guess one day I'll be forced to
> redesign it around a SHARC, but I haven't found the
> assembler and header files cheap/free for those yet. I
> think the cheapest way into SHARCs is the BeastRider
> IDE.

got any links to that IDE? I've not heard of it.

Paul 




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