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DSP question , cascading functions

Discussion in 'Electronic Design' started by RealInfo, Mar 18, 2013.

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  1. RealInfo

    RealInfo Guest

    Hi all
    I hope I came to the right group

    My question is general DSP question .

    In case I need 2 DSP functions to be done on the same
    analog signal one after another, for example a low pass filter firs function
    and on the result a noise reduction function .

    My question is : can the 2nd function be done on the digital
    byte stream of the 1st DSP hardware block , or the 1st output should be filtered and the 2nd DSP function will be done on the
    analog signal derive from 1 DSP ?

  2. Uwe Hercksen

    Uwe Hercksen Guest


    that is a problem of the sampling frequency and the time needed to
    compute the first and the second function. If the sampling requency is
    40 kHz, one sample must be computed in less than 25 µs. If both
    functions are done in less than 10 µs for each, it is possible within
    one DSP, if less than 20 µs you will need two DSPs.

  3. Robert Macy

    Robert Macy Guest

    can it not be 'pipelined' and simply delayed? The first function is a
    simple low pass, of sorts. Memory would only take enough memory
    samples to represent the low frequency cutoff, right?
  4. josephkk

    josephkk Guest

    Just the same, the only real question is can you get all the tasks done on
    time. This is a simple hard real time thing. OTOH the comm time to hand
    it off to a second DSP for the next stage may kill the timing.

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