fir_pcm.c

教程《DSP 原理及其 C 编程开发技术》中的源代码

//Fir_pcm.c FIR using PCM3003 codec

#include "bp41.cof"		     //coefficient file BP @ Fs/8
int yn = 0;				     //initialize filter's output
short dly[N];                      //delay samples
float Fs = 48000.0;		     //fixed/actual Fs

interrupt void c_int11()	     //ISR
{
  short i;
  
  dly[0] = input_left_sample();    //newest input @ top of buffer
  yn = 0;                          //initialize filter's output
  for (i = 0; i< N; i++)
		yn += (h[i] * dly[i]); //y(n)+=h(i)*x(n-i)
  for (i = N-1; i > 0; i--)        //starting @ bottom of buffer
   		dly[i] = dly[i-1];     //update delays with data move

  output_right_sample(yn >> 15);   //output filter
  return;				     //return from ISR
}

void main()
{
  comm_intr();                     //init DSK, codec, McBSP
  while(1);                        //infinite loop
}