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LAUNCHXL-F280049C: Viterbi Decoding

JMT82
Prodigy 90 points

Part Number: LAUNCHXL-F280049C
Other Parts Discussed in Thread: C2000WARE

I am working on developing a viterbi decoder using the LAUNCHXL-F280049C.  I see from the F280049CPZS microchip on the LAUNCHXL has a built in hardware viterbi decoder.  I was wondering if there were any libraries available to help configure the decoder.  All I was able to find was a couple of examples that were written in assembly for a specific decoding method.  I did not see a generic library to configure various viterbi polynomials.

Thank you

  • 0
    TI__Mastermind 27145 points

    Have you looked at this directory within C2000Ware? It has source, libs, examples, etc.

    \libraries\dsp\VCU\c28

    Thanks,

    Sira

  • 0 in reply to Sira Rao80
    Prodigy 90 points

    Hello, yes I have looked at the examples for both the VCU0 and VCU2.  (I have a second dev board that supports VCU2).  I do not see in the example code where the polynomial is set.  From looking at the some of the documentation I have found, SPRU533D et.al. it looks like the VCU should support arbitrary polynomials.  I see some comments in the example code where they say what polynomial is used, but I don't see where that value is being set.

    Thank you.

  • 0 in reply to JMT82
    TI__Mastermind 27145 points

    I don't have a great answer here. This is something we haven't and don't actively support.

    Online search seems to indicate the following:

    The convolutional code with a constraint length (K) of 7 and a code rate (CR) of 1/2, commonly used in satellite communications, is defined by two generator polynomials. These are often expressed in octal form
    . 
    The polynomials are:
    G1 = 171 (octal)
    G2 = 133 (octal)
    For K=4, CR = 1/2, it's G1 = 15 (octal) and 13 (octal), or in some cases 17 and 13.