fir.c

DSK6713的FIR滤波器的程序 可以用来做为FIR滤波

#include "short6713cfg.h"
 
#include "dsk6713.h"
#include "dsk6713_aic23.h"

#include <stdio.h>
#include <math.h>
/*
  ------------------------------------------------------------------------------
  Defines
  ------------------------------------------------------------------------------
*/
#define pi 3.1415927
#define Length 512
/*
  ------------------------------------------------------------------------------
  Function prototyping
  ------------------------------------------------------------------------------
*/

/* Codec configuration settings */
DSK6713_AIC23_Config config = { \
    0x0017,  /* 0 DSK6713_AIC23_LEFTINVOL  Left line input channel volume */ \
    0x0017,  /* 1 DSK6713_AIC23_RIGHTINVOL Right line input channel volume */\
    0x01f9,  /* 2 DSK6713_AIC23_LEFTHPVOL  Left channel headphone volume */  \
    0x01f9,  /* 3 DSK6713_AIC23_RIGHTHPVOL Right channel headphone volume */ \
    0x0011,  /* 4 DSK6713_AIC23_ANAPATH    Analog audio path control */      \
    0x0000,  /* 5 DSK6713_AIC23_DIGPATH    Digital audio path control */     \
    0x0000,  /* 6 DSK6713_AIC23_POWERDOWN  Power down control */             \
    0x0043,  /* 7 DSK6713_AIC23_DIGIF      Digital audio interface format */ \
    0x0081,  /* 8 DSK6713_AIC23_SAMPLERATE Sample rate control */            \
    0x0001   /* 9 DSK6713_AIC23_DIGACT     Digital interface activation */   \
};

/*
  ------------------------------------------------------------------------------
  Global variables
  ------------------------------------------------------------------------------
*/
double npass,h[51], x, y, xmid[51];
float in[Length], out[Length];
int m=50;
int n=256;
double fs,fstop,r,rm;
int i,j,p,k=0;
int x_in;
// Left and right signal samples
Uint32 xL, xR;
//================================================================       

  void firdes (int m, double npass);

/*
 *  main() - Main code routine, initializes BSL and connects input samples
 *           to output samples in an infinite while loop.
 */

/* The main programme of FIR  */

void main()
{
    // Codec data handle structure
    DSK6713_AIC23_CodecHandle hCodec;
	//Define filter variables
    /* Initialize the board support library, must be called first */
    DSK6713_init();
     
    /* Start the codec */
    hCodec = DSK6713_AIC23_openCodec(0, &config);
    // Set sampling frequency via the number before KHZ in the define.
    // Choose from 8, 16, 24, 32, 44.1, 48, or 96 Khz.
    DSK6713_AIC23_setFreq(hCodec, DSK6713_AIC23_FREQ_32KHZ);
           
  	fs = 32000;
  	fstop = 1000;
  	npass = fstop/fs;    

  	for (i=0; i<=m; i++)
  	{
  		xmid[i]=0;
  	}

  	firdes(m, npass);
  	
// Infinite loop so that we can continue to process samples forever 
    while(1)
    {
		// read A/D
		
		while (!DSK6713_AIC23_read(hCodec, &xL));
      	while (!DSK6713_AIC23_read(hCodec, &xR));

		x_in = (Int16) xL;
		x = (float) x_in;
		in[k] = x;
		
		for (p=0; p<=m; p++)
   		{
   			xmid[m-p] = xmid[m-p-1];
   		}
   		
   		xmid[0] = x;
    
		r = 0;
		rm= 0; 
		for (j=0; j<=m; j++)
		{	
 		 	r  = xmid[j] * h[j];
			rm = rm + r;
   		}
		y = rm;
		
		out[k] = y;
      	xL = (int)(y);
		
		while (!DSK6713_AIC23_write(hCodec, xL));
        while (!DSK6713_AIC23_write(hCodec, xL));
		
		k++;
		k = k%Length;
						
		if (k == 0) 
		{
			k = 0;
		}	

    }

    /* Close the codec in theory, but unreachable with the above while loop*/
    //DSK6713_AIC23_closeCodec(hCodec);  
}	

//================================================================     
//================================================================     

void firdes(int m, double npass)
{
  	int t;
   	for (t=0; t<=m; t++)
  	{
  		h[t] = sin((t-m/2.0)*npass*pi)/(pi*(t-m/2.0));
  	}
  	if (t=m/2) h[t]=npass;
}