CIC mittels C implementieren

Hallo,

ich bin gerade dabei ein CIC Filter zur SampleRate Reduzierung zu 
entwerfen (dsPic). Jedoch bin ich mir nicht ganz sicher, ob ich es 
richtig umgesetzt habe. Vielleicht hat noch jemand Anregungen für 
Verbesserungen.

Es müssen NumbOutputSample * DecimationFactor Inputsamples im 
Eingangsarray vorhanden sein.

Ich bin mir deswegen unsicher, da bei konstanten Eingangssamples eine 
Verstärkung >1 auftritt.

Stefan




typedef struct
{
  uint16 R;      // decimation factor
  uint16 N;      // number of stages
  uint16 M;      // comb delay, select 1 or 2 (not used now)
  int32 *intDelay;    // ptr to delay array
  int32 *combDelay;    // ptr to comb delay array
} CICStruct;


// protoype declaration
void CIC (               // CIC filtering
   uint16 numSamps,         // number of input samples (N)
          // N = R*p (p integer)
   int16 *dstSamps,           // ptr to output samples
                                        // (y[n], 0 <= n < N)
   int16 *srcSamps,           // ptr to input samples
                                        // (x[n], 0 <= n < N*R)
   CICStruct *filter            // filter structure:
);


void CIC (uint16 numSamps, int16 *dstSamps, int16 *srcSamps, CICStruct 
*filter)
{
  uint16 i;
  uint16 i_cic;
  uint16 samples = 0;
  int32 tempX;  // holds value between CIC stages
  int32 combY;

  for(i = 0; i < numSamps; i++)
  {
    // save new input sample into variable
    tempX = (int32)*srcSamps;

    // process for all N CIC stages
    for(i_cic = 0; i_cic < filter->N; i_cic++)
    {
      // y[n] = x[n] + y[n-1]
      tempX = tempX + *(filter->intDelay + i_cic);
      // make y[n] to y[n-1] for next loop
      *(filter->intDelay + i_cic) = tempX;
    }//for stages

    // select next input sample
    srcSamps++;
    samples++;

    // decimation and COMB filter
    if (samples == filter->R)
    {
      samples = 0;
      // process for all CIC stages
      for(i_cic = 0; i_cic < filter->N; i_cic++)
      {
        // backup x[n]
        combY = tempX;
        // y[n] = x[n] - x[n-1]
        tempX = tempX - *(filter->combDelay + i_cic);
        // make: x[n] to x[n-1] for next sample
        *(filter->combDelay + i_cic) = combY;
      }//for stages

      // save to output and select next output destination
      *dstSamps = (int16)tempX;
      dstSamps++;
    }//if COMB

  }//for numSamps

}//CIC