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DSP System

Discussion in 'Electronic Design' started by Jon Slaughter, Jul 20, 2007.

  1. How hard is it to actually implement a DSP system?


    I've been looking at the TMS320C6720 and some conversion devices and it
    seems I can gather all the components needed but I really don't have a good
    idea about how to go and implement something like that. The pdf's I've
    looked at on TI's don't really go into detail about how to actually put
    something together(atleast the one's I've seen).

    All I want to do is take an analog signal, add some digital filtering(well,
    whatever I want once I get into the software side), and output the signal.

    The digital conversion's seems pretty straight forward and I was plan on
    using something like the PCM1741 and PCM1807 or something similar for the
    conversion(although I ultimately want to go to 192khz).

    I think all I'll need is the converters, memory, and the dsp? (I don't think
    I'll need a controller?) Is it going to be much harder than just hooking all
    these up together and then downloading some code to the dsp?

    At this point I do not need anything fancy and just want to apply some
    effects like reverb and chorus to a signal for a start. The biggest problems
    at this point is the IC packaging for these devices as most are out of my
    reach(BGA, for example) for prototyping.

    Is such a conceptually simple project out of my ability as a hobbyist? Do I
    need to come up with some prototyping schematic and get some pcb's made for
    prototyping? I'm really not sure how to go about this and I can't find any
    documents online that can give me some details about the process ;/


    Any ideas?
    Thanks,
    Jon
     
  2. What you need is a DSP development board. They will usually contain
    all you need to get a project like this off the ground - the DSP chip,
    any required memory, a few ADC inputs and DAC outputs etc, many are
    targeted specifically for audio use. It's already done for you.
    TI have a complete range of them:
    http://focus.ti.com/dsp/docs/dspsupporttnp.tsp?sectionId=3&tabId=2079&toolTypeId=1&familyId=44

    They aren't particularly cheap, but it can save you weeks of mucking
    around with hardware, when really a project like this is all about the
    software.

    There is nothing really special about DSP's, they are essentially just
    a microprocessor with specilised hardware making them faster at math
    and signal processing functions than a regular microprocessor or
    microcontroller.

    Dave.
     
  3. I've looked at that but I can justify the expense. Its got, what, about
    20-30$ worth of components and another 20-30$ for the pcb (if that) yet they
    want 400 for just a starter? If theres something I'm missing that makes it
    worth it then please let me know about it but it seems like its not worth
    it.

    Jon
     
  4. You are paying for the convenience, it's called "starter" for reason,
    it gets you started with no with fuss and no wasted effort, productive
    from day one.
    You might be able to build it for less, but how much is your time
    worth?
    You have to design your board and get it made, and all the research
    that goes along with that. Get the parts in one-off qty that aren't
    always available as such. Then you have to sort out the software tools
    and libraries etc etc

    There are others available, but prices are similar, try this Blackfin
    DSP audio kit:
    http://www.analog.com/processors/platforms/ask.html
    http://www.analog.com/en/prod/0,2877,BF537%2DHARDWARE,00.html

    It's got everything you need for audio DSP development, tons of memory
    and I/O etc, plus all a whole bunch of software tools.
    Digikey have it for $371.

    Analog devices have other ranges of Audio development kits in their
    SHARC, TigerSHARC, Blackfin and ADSP-2100 platforms.

    Dave.
     
  5. I forgot to mention that you don't need a DSP for audio processing
    these days, many of the 16/32 bit processors on the market can easily
    handle it. You might be able to score a processor development kit with
    an audio interface for cheaper than the DSP offerings perhaps.

    Dave.
     
  6. Isn't that part of the fun though? I'll eventually have to do that anyways.
    The only reason I would want the board is so I have some guide lines on how
    all the components fit together(since I can't seem to find any documentation
    to help) and because if/when I do it myself I know I'll **** it up and spend
    days or weeks if not months on some stupid little thing.
    I was just looking at that. It was about 300$ direct. The Blackfin seems
    pale in comparison to the TMS series though. The Shark seems to be decent
    though.

    I think I'm just going to try and design a board myself. It may or may not
    work but I suppose I can post my results here and get a little help. It just
    seems it will be a few months before I can even start unless I can find some
    good documentation. The EVM is pretty nice in that it has a bunch of stuff
    but I don't think I need it all and most likely its overkill. Its nice to
    have but I wouldn't want to waste 500$(min since I'll need software stuff
    too) if I don't follow through with the project I have in mind(although it
    would be nice to have around but not for the price).

    I'll see what I can come up with though. Trying to gather some info on it
    now. The TMS datasheet just didn't give me much hope for finding good info.

    Thanks,
    Jon
     
  7. Yes but I think ultimately this is what I want to learn since I have a lot
    of projects I would like to eventually work on that involve signal
    processing(all audio stuff). Although I was initially planing on doing it
    with the pc, I think it will be much more interesting to do it using a DSP
    processor(and I think it will be more enjoyable if I'm able to put together
    the hardware for it instead of just doing software).


    Thanks,
    Jon
     
  8. It depends.
    If all you need is filtering the audio signal and some effects, the simplest
    solution would be a digital audio processor. Consider TAS3004 from TI. It
    does have the stereo codec built in. There are also many newer DAPs made by
    AD, TI, Cirrus Logic, NXP, AKM and others.
    You will probably need a flash memory.
    Well. The hardest part is to get "some code" to work.
    Consider buying a DSP evaluation board.
    It is not a rocket science however it requires time and effort, as
    everything.
    You can use schematic of a DSP evaluation board as a reference.

    Vladimir Vassilevsky
    DSP and Mixed Signal Consultant
    www.abvolt.com
     
  9. That hardware is essentially the same regardless of whether you use a
    micro, DSP, or FPGA with a processor soft core, the only real
    difference is in the speed of processing. In fact FPGA's are becoming
    very popular these days for DSP processing, with all sorts of DSP
    hardware slices built in to the FPGA fabric, that's where the future
    seems to be. But that is a much more difficult learning curve than a
    DSP processor.

    If you write your code portable enough in C, the bulk of he software
    will be the same regardless of the hardware used. You can do the
    software development on the PC with a sound card and then port it
    fairly easily to your DSP chip and dedicated hardware.

    I can appreciate wanting to do the hardware aspect yourself though,
    have fun!

    Dave.
     
  10. Nico Coesel

    Nico Coesel Guest

    I'd choose an Analog Devices. These are much more suitable for general
    purpose processing than the TI components. There is also a big user
    base and free tools. Just google for Blackfin and gcc.
     

  11. I second on the AD DSPs. There is more common sense in the ADI CPU
    architecture compared to that of TI. The documentation is more
    convenient also.

    Yes, for those who like the junk code there is a lot of it.


    Vladimir Vassilevsky

    DSP and Mixed Signal Design Consultant

    http://www.abvolt.com
     
  12. The TAS does not seem to have any DSP like features and the filters are
    built in. I need more control because I want to design my own(although
    nothing that hasn't been done).
    Yeah. TI doesn't seem to make memory? Not sure where to go with that and
    not sure if I can find something that is "plug in play"(that isn't going to
    require any controllers or anything).
    If you mean from the hardware perspective then I agree(in that I need the
    hardware setup properly to get the software to work)... but I'm a lot more
    comfortable with coding than I am with building "complex" circuits(its
    mainly that a **** up, which I do a lot, is pretty costly in hardware
    compared to software).
    I've considered it but I think I'll try and roll my own.
    It was something I was looking for but where can I get such a thing?
    Specifically for TI as I think I'm more interested in the TMS then anything
    else I saw.

    Thanks,
    Jon
     
  13. Yes and that is something else I've been wanting to get into ;) DSP's though
    just seem more direct at this point and I have all the stuff to do it(just
    not necessarily to do it well). Again, the main issue with the DSP seems to
    be the documentation. I guess I just need to spend more time reading it
    though.
    True. The majority of the project is standard stuff though so I think the
    main issues are the hardware and dsp specific stuff.

    I hope ;)

    Thanks,
    Jon
     

  14. Seems though that the components are less powerful for the same price(or
    more)? I'll look into it some more though. Just glancing over the
    datasheets for the Blackfin was pretty disappointing compared to the TMS. Of
    course I'm probably comparing apples and oranges.

    Thanks,
    Jon
     
  15. Nico Coesel

    Nico Coesel Guest

    Don't just stare at megahertz and mips. AD has a long track record in
    DSPs and they know what they are doing. If you want to make a good
    comparison, you'll really need to figure out how powerfull the
    instruction set is and how well the peripherals unload the CPU by
    using FIFOs and DMA.

    Some processors may need -say- 10 instructions to perform a certain
    operation while others processors may be more clever and only need 1
    instruction. If the first processor can do 10mips and the second
    processor does 2mips, the second processor will still be twice as fast
    as the first.
     
  16. Nico Coesel

    Nico Coesel Guest

    If you are going to build your own circuit you'll have to get your
    hands dirty and go through all that anyhow. A starter kit is nice, but
    the limits are usually reached quite soon (like having no room for
    surface mounted components). I mostly design my own starter kits
    (based on diagrams from existing starter kits) which only contain what
    I really need to evaluate.
     
  17. Have you done anything like this and if so how did you start? The thing I'm
    worried about is all the trouble to set it up then miss something. As far as
    I see it, its mainly just routing and there are few little things like the
    power supply and power issues involved but because I can't seem to find
    anything on how to do even a basic dsp I'm worried I'll easily miss a lot of
    things ;/ The datasheets only seem to talk about very specific things but
    really how to connect the different components. (I do understand most of its
    routing but I guess I just need to see what someone else has done and what
    works)

    Thanks,
    Jon
     

  18. Sure... I guess if I can find a cheap DSP and some instructions on how to
    setup the hardware then I might go with that. Since it would be the first
    time its better that I finish than worry about the speed of it. I really
    need to spend more time at AD's sight ;)

    Thanks,
    Jon
     
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