[sdiy] The Chameleon Guitar

[Paul Maddox]

Csaba,

   Ok, I like DSPs, I'm not ashamed to admit it.

  FWIW, the toolchain isn't that different, as you say, the use of  
eclipse and freescale now standardizing on toolchain for their  
products is very very welcome.

  You *can* write code for a DSP in C, there's nothing to stop you,  
there's cross compilers out there. BUT, to get the best from a DSP you  
need to get into the assembly language. The beauty of the assembly  
language on the freescale DSPs is that you can do an instruction and  
up to two memory moves in the SAME clock cycle.

for example

MPY	X0,Y1,B		#0.3,Y0

This multiples, reg X0, by reg Y1 and stores the result in B
at the _SAME_ time it moves a value of 0.3 into reg Y0

here's another one ;-

ASL	A		B,X:(R_X)+

Logical shift left of register A whilst copying the B register into  
the X memory location held in register R_X and then this register is  
incremented.

C compilers currently can't cope with this level of optimisation.
so to code truly effeciently in DSP you'll need to start wrapping your  
head around assembly language, but to do it quickly you can code in  
C :-)

The DSP assembly code really isn't that hard to learn, there are a few  
commands you need to learn, and once you start programming it becomes  
second nature.

I'm no DSP guru, but I kinda of enjoy programming in assembly, it  
feels "real".

Paul
P.s. those examples are taken from the filter in the Monowave II.



On 8 Apr 2009, at 20:31, Csaba Zvekan wrote:

> I see your point Eric & Tom on the lack of necessary I/O's ADC,  
> UARTS but disagree with the software . Freescale is using their  
> "Symphony Studio " which is nothing more than a pre-compiled Eclipse  
> "Ganymede"/GCC/GDB, OpenOCD version with most likely some of their  
> core-plug ins (if even that is true).
> And if you played around with GNUARM / Eclipse for like ARM  
> processors then this tool is exactly the same.
> I mean I am no way a guru in DSP56xx programming but rather hate to  
> see my little SoundBite board up on the top shelf, unused.
> There's gotta be something we can do with them even if it's a filter  
> bank , FX or something for our SDIY Modulars. Maybe we hook up a 8- 
> bit µCU with some encoders,  display & MIDI I/O and update DSP  
> registers via SPI .
> I believe some of the code that is being written over on Line6's  
> ToneCore for a smaller DSP56xx could be analyzed and ported.
> But it is true what Tom says you would have to take the time and dig  
> in that DSP . And everyone knows a lot of the DSP functions if not  
> all can be done with ARM & FPGAs.
>
> I say : "Too many ideas never enough time " :)
>
> Csaba
>
> On Apr 8, 2009, at 6:34 PM, Tom Wiltshire wrote:
>
>> I have to agree with Eric on this one. My Soundbite board is  
>> currently sat on the shelf too. This is not because it's not a good  
>> board - it is; 4 stereo ins and outs, 24 bit processing at 400MHz,  
>> etc etc..something like that anyway. The problem is exactly what  
>> Eric identifies. You need to learn your way around a load of new  
>> software to program it (and this is not some neat and tidy single  
>> tool, but a group of applications. Once you've done that and you're  
>> in, you've got to learn how to deal with a DSP. All in all, it's a  
>> pretty big job.
>>
>> I'd love the power that something like Soundbite would give me. I  
>> could write some killer digital sound generation stuff with it. I  
>> vaguely had it in mind to use it as the heart of four hybrid voice  
>> modules. Each stereo out would then go to individual analog  
>> processing on a per-voice basis. This is such a cracking idea that  
>> I'll probably have to get to it at some point. Like he said, "Fun  
>> if you're into it but I had other things to do".
>>
>> T.
>>
>>
>> On 8 Apr 2009, at 17:01, Eric Brombaugh wrote:
>>
>>> Csaba Zvekan wrote:
>>>> This is really cool idea . Are there any other projects with the  
>>>> SoundBite board?  I happened to have that board too as some of  
>>>> you as well. I was wondering if we can get more out of the  
>>>> SoundBite board than just the demo tones and passthrough .
>>>> Has anybody digged some more into the DSP56371.
>>>> Maybe we can set up some sort of a repository and share our  
>>>> codes . Kind of like Line6 is doing with their DSP based ToneCore  
>>>> stampbox .
>>>> Always interested in making some noisy boxes :)
>>>
>>> The guy at Freescale who spearheaded the SoundBite board was  
>>> pretty enthusiastic and posted a lot of support material on the  
>>> Freescale site. I think Paul Maddox was pretty serious about  
>>> trying to do some things with it for a while and set up a forum  
>>> for it that seems to have been shut off now.
>>>
>>> The biggest problem with the SoundBite board was the fairly  
>>> complex development environment (Eclipse + OpenOCD + GCC) and a  
>>> lack of standard I/O devices. The DSP chip has some GPIO and a  
>>> host SPI port, but no ADCs, UARTs, etc. It would make a good  
>>> peripheral under the control of another chip for MIDI processing  
>>> and/or CVs & knobs, but that requires addition hardware work.
>>>
>>> Although the development tools are C-based, using the DSP  
>>> capability of the processor requires getting down into the  
>>> assembly language. Not impossible, but you do have to learn yet  
>>> another processor architecture.
>>>
>>> Overall it's a pretty big pile of stuff to absorb. Fun if you're  
>>> into it but I had other things to do. :)
>>>
>>> Eric
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>>
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