lowpassfilter.c

一个滤波器和一个音效处理程序 TI 的CCS 编译器编程。

#include   "LowPassFilter.h"



#define McBSP0_DRR2  (*(volatile unsigned int *)0x0020)
#define McBSP0_DRR1  (*(volatile unsigned int *)0x0021)
#define McBSP0_DXR2  (*(volatile unsigned int *)0x0022)
#define McBSP0_DXR1  (*(volatile unsigned int *)0x0023)

/***********************************************************************
**  Function Routine
***********************************************************************/
void  LowPassFilter(void)
{

      
      /* mix microphone input with the carrier to shift frequency */
      pMicPhIn  = ((McBSP0_DRR1-130) << 0 )&0xFFFE;      
      //SInMx    = ((long int)(MicPhIn * SCarrier) >> 16);
      pSInMx    = pMicPhIn;
      //McBSP0_DXR1     =  McBSP0_DRR1;
		//McBSP0_DXR1    &=  0xFFFE;
      /* filter the mixed signal with a 2nd order filter */
      pSOutTemp1 = pSInMx*pb0;
      pSOutTemp2 = pSInMxZ1*pb1; 
      pSOutTemp3 = pSInMxZ2*pb2;
      pSOutTemp4 = pSOutZ1*pa1;
      pSOutTemp5 = pSOutZ2*pa2;
      pSOutTemp  = pSOutTemp1 + pSOutTemp2 +pSOutTemp3 -
                  pSOutTemp4 - pSOutTemp5;
      McBSP0_DXR1     =  pSOutTemp >> 12;  // scaled signal output 
      McBSP0_DXR1    &=  0xFFFE;

      // update 1st and 2nd order delayed input& output 
      pSInMxZ2  = pSInMxZ1;
      pSInMxZ1  = pSInMx;
      pSOutZ2   = pSOutZ1;
      pSOutZ1   = pSOutTemp>>16;

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