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Old 25th November 2004, 11:02 AM   #1
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Default DSP (offering) Survey

Hello all,

I am investigating whether it is worth buying, distributing and servicing a certain DSP quite suitable for DIY audio purposes.

Below are the specs:
multiplier 24 x 12 bit
dual harvard
4 x i2s in
4 x i2s out
1 x DA
Programmable PLL
2 x SPDIF In (muxed)
70 MIPS

1.5k word Program memory
2 k word data memory (24 bit)
1.5 K word coefficient memory (12 bit)

With 2 multiplications dual precission calculations are possible.

Available tool is the assembler only.

My idea is to :
- supply you with IC's
- make kits with IC, board and tool
- make a full digital crossover board

What do you think ?


grtz

Simon
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Old 26th November 2004, 05:37 AM   #2
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No one ?

grtz

Simon
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Old 26th November 2004, 05:49 AM   #3
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One opinion.
It seems to fall between two stools. For those skilled in the art as they say, it's too little. One could do more on a low cost FPGA or DSP EVB. For those not skilled in the art, assembly language programming may well be too much to ask and one of those join-up-the-boxes type tools would put it beyond the reach of most, assuming one is even available for said chip.
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Old 26th November 2004, 06:08 AM   #4
hjelm is offline hjelm  Sweden
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Depending on the DSP itself i would say that assembler is maybe not enough, i could probably cope but it takes time to learn a new processor at assembler level.
As for processing power does the multiply take more than one cycle and how about memory fetches?
Are there any MAC operations available in the processor or does it take the extra add cycle.

All in all it would be a cost and ease of integration issue if i was to buy one.
A slight suggestion if you are to make boards, reclock the I2S outputs in an intelligent manner.
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Old 26th November 2004, 06:26 AM   #5
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Quote:
One could do more on a low cost FPGA or DSP EVB. For those not skilled in the art, assembly language programming may well be too much to ask and one of those join-up-the-boxes type tools would put it beyond the reach of most, assuming one is even available for said chip.
I can assure you that creating Filters in an FPGA is far more complex than using an DSP !
Ever wondered how to create a Multiplier / adder and etc ????
How to create a circular buffer for coeffiecents and data ?
Not talking about I2s receivers and transmitters !

Or are you willing to buy such mega functions ? I am not !

Idea is to create an open library wherein knowledgable will contribute to the lesser knowledgable.

Quote:
Depending on the DSP itself i would say that assembler is maybe not enough, i could probably cope but it takes time to learn a new processor at assembler level.
It is 56000 a like

Quote:
As for processing power does the multiply take more than one cycle and how about memory fetches?
All 1 instruction cycle.

Quote:
Are there any MAC operations available in the processor or does it take the extra add cycle.
You can do a multiplication add and 2 moves (coef and data) in 1 cycle. But not in all cases.

Quote:
All in all it would be a cost and ease of integration issue if i was to buy one.
A slight suggestion if you are to make boards, reclock the I2S outputs in an intelligent manner.
OK. Good suggestion


grtz



Simon
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Old 26th November 2004, 06:38 AM   #6
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It was just an opinion but if you feel so strongly about it I apologise and we can agree to disagree.
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Old 26th November 2004, 06:58 AM   #7
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Quote:
It was just an opinion but if you feel so strongly about it I apologise and we can agree to disagree.
apologies if i offended you !

I investigated different options my self, since i became intrigued by digital (dsp) x-overs.

FPGA's was one of them.
Problem with FPGA's is that it becomes fastly more complex.
You need to keep in mind the package and amount of gates, knowledge of verilog/vhdl and the more indepth knowledge of multipliers/adders versus speed and logic size.

But if i had more time............... i would certainly try it.


grtz

Simon
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Old 26th November 2004, 07:30 AM   #8
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I've been using these things since the days of the XC3000 and I have some measure of what they can do. HDL's are a side issue. One has to first understand the logic being described and if one does then it becomes apparent some things are more suited to FPGA's than DSP chips but each to his own.
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Old 26th November 2004, 12:28 PM   #9
gmarsh is offline gmarsh  Canada
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Well, having some information on what DSP you're talking about (a part number or datasheet) would certainly help. I'm not going to buy a random DSP until I know exactly what it has for packaging, required voltages and power requirements, I/O & peripherals, RAM architecture and addressing capabilities, some idea of what the instruction set looks like, yadayadayada...

Until I get this info, I'll stick with my SHARC and Blackfin evaluation boards.

And I will agree, doing FIR filters in a FPGA is harder - hand-coding a FIR in Verilog is a pain in the *** (been there, done that) and using an easy FIR filter block invariably involves buying a $$$ set of design tools. But the only place when you'll really want to do that is when you're using excruciatingly high data rates where a DSP just doesn't have the processing capabilities.
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Old 26th November 2004, 01:56 PM   #10
macboy is offline macboy  Canada
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IMHO, the mathematical precision of the DSP in question is quite bad. Multiplier is 24x12 and coefficients are 12 bits? :-P

If a person wants simply to make a digital crossover, a much much better and easier solution is to use a product like TI's TAS3103 DSP. It is not a general purpose DSP, so you can only do what it does, but what it does is 16 IIR filters per each of 3 channels, plus a whack of mixing/3D effects including delay (good for lip sync), dynamic range exp/comp, and a lot more. It has almost infinitely better precision than the aforementioned DSP, with 48x28 multiplies and 28 bit coefficients. All that you need to do is configure it with EQ coefficients, etc., which is a lot easier than writing code from scratch. Its inputs and outputs support 16 to 32 bits in just about every format you've ever heard of, and it interfaces directly with DACs and ADCs or DIRs.
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