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TMS320C6713 DSK Disable filters

Nicholas Cheng
Prodigy 170 points

Hi,

Does anyone know how to disable the TMS320C6713 DSK A/D and D/A filters? To be more specific, how to turn off the A/D and D/A filters of the AIC23 codec on the board? This is important as I do not want my input data (looking at infrasound frequency ranges <20Hz) to be filtered out. 

Thanks.

Regards,

Nic

  • 0
    TI__Guru* 84110 points

    Nic,

    Are you asking about the R-C filters on the board? If so, they cannot be "turned off" without modifying the board.

    If not, which filters are you asking about?

    Regards,
    RandyP

  • 0 in reply to RandyP
    Prodigy 170 points

    Hi Randy,

    Thanks for the reply. Yes, I am asking about the RC filters on board. In my project, I need to work with signals below 20Hz...I am worried that the high pass filter would cause some problems. Based on the drawings, I calculated the cut off freq by 1/(2*pi*R*C) = 1/(2*pi*4700*470*10^-9) = 72 Hz. Does anyone else agrees with this value? I have read some forums stating it was 400Hz, but I just cant believe this value. Btw Randy, do you know how to bring this down to about 1 or 2 Hz by adding or desoldering some components?

    Thanks,

    Nic

  • 0 in reply to Nicholas Cheng
    TI__Guru* 84110 points

    Nic,

    Modifying a board will usually invalidate the warranty, if there is one left on your board. If this is a concern, please contact the board vendor to confirm before making any modifications.

    Rs and Cs are not my strong point, so I will leave that to your calculations. You can easily run tests with a signal generator or oscilloscope to see where the signal starts to shrink.

    An alternative would be to check the Internet for add-on board vendors. I expect there are a variety of compatible ADC/DAC cards available for the C6713 DSK. If you find one, please reply back here to let others know what you chose and also how it works for you.

    It sounds like you are more interested in a low-pass filter to make sure low frequencies get in but high frequency noise does not. Running with no filter might be just as good for you if your environment does not introduce much noise. Other than these suggestions, I am not sure what more I can help with. Someone else may have some comments for you.

    Regards,
    RandyP

  • 0 in reply to RandyP
    Expert 2210 points

    I think most of the TI A/D Evaluation Modules (which use the 5-6K Interface Board and DAP signal preconditioner) have only low-pass filtering (done in the DAP).  That was the case for the THS1206EVM that we're using.  We modified our DAPs to raise the cut-off to a couple of MHz.