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/***********************************************************************
**  File Name:    SecurityVoice.c
**  Part Number:  TLV320AIC10/11EVM-SW-00005
************************************************************************
**  Copyright (c) Texas Instruments, Inc. 2000
************************************************************************
**
**  Release History:
**     Version      Date          Engr          Description
**      1.00     10-11-2000    Wendy X Fang   Original Release
**
************************************************************************
**
**  Function:
**     This program changes microphone input signals spectrum so that
**     the voice from the microphone can NOT be recognited. The function
**     is obtained through a signal mixer and a band-pass filter. That
**     is:  SOut(t) = filter( SIn(t)*SCarrier(t) ), where the single
**     SINE tone SCarrier(t) with frequency = 2000~4000Hz. This program
**     runs under the main frame with a rate of 16KHz and all signal
**     sample rates are also 16KHz.
**
***********************************************************************/
/***********************************************************************
** Include Statements
***********************************************************************/
#include   "SecurityVoice.h"

/***********************************************************************
**  Function Routine
***********************************************************************/
void  SecurityVoice(void)
{
      /* compute the carrier sine signal */
      SCarrierInd += 3;             /* increase carrier SINE index  */
      if (SCarrierInd >= 23)        /* limit the index within table */
         SCarrierInd = 0;    
      SCarrier = f697[SCarrierInd]; /* carrier SINE freq = 3*697Hz  */
/*    SCarrier = f1209[SCarrierInd];   carrier SINE freq = 3*1209Hz */

      /* mix microphone input with the carrier to shift frequency */
      MicPhIn  = ((SL_ADC-130) << 4 )&0xFFFE;      
      SInMx    = ((long int)(MicPhIn * SCarrier) >> 16);

      /* filter the mixed signal with a 2nd order filter */
      SOutTemp1 = SInMx*b0;
      SOutTemp2 = SInMxZ1*b1; 
      SOutTemp3 = SInMxZ2*b2;
      SOutTemp4 = SOutZ1*a1;
      SOutTemp5 = SOutZ2*a2;
      SOutTemp  = SOutTemp1 + SOutTemp2 +SOutTemp3 -
                  SOutTemp4 - SOutTemp5;
      SOut     =  SOutTemp >> 10;  /* scaled signal output */
      SOut    &=  0xFFFE;

      /* update 1st and 2nd order delayed input& output */
      SInMxZ2  = SInMxZ1;
      SInMxZ1  = SInMx;
      SOutZ2   = SOutZ1;
      SOutZ1   = SOutTemp>>16;

      /* output the secured voice to master AIC10 device in ISR */
}
/***********************************************************************
**  End of File -- SecurityVoice.c
***********************************************************************/