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TIDA-00011 Help

hank chen
Prodigy 20 points

Hi,

I have requested the TIDA-00011 source code. In the code, there is a "filter(sample)" function. I want to know the principle about this function .

Can you give me some help? THx

  • 0
    TI__Prodigy 30 points

    Hi Hank,

    The filter function is an implementation of a 3rd order bandpass butterworth IIR filter as a "second order section" (sos) implementation. The following loop is a simplification of the same code (with gain removed, and scaling factors removed):

    for (i = 0; i < STAGES; i++)
    {

    wn = input - a[i][0] * dly[i][0] - a[i][1] *dly[i][1];
    result = b[i][0]*wn + b[i][1]*dly[i][0] +b[i][2]*dly[i][1];
    dly[i][1] = dly[i][0];
    dly[i][0] = wn;
    input = result;
    }

    Let me know if this answers your question.

  • 0 in reply to Vitali Loseu
    Prodigy 20 points

    Hi Loseu,

         I get it . Thank you very much!