fir.c

DSP系统入门与实践源代码

/***************************************************************************/
/*                                                                         */
/*     Experiement1 . C                                                    */
/*                                                                         */
/*     File In/Out and processing in a main loop                           */
/*                                                                         */
/*                                                                         */
/*     2004/04/04                                                          */
/***************************************************************************/

#include <stdio.h>
#include <math.h>

#define TRUE 1
#define FALSE 0

#define N 8

#define BUFSIZE 100  /* the buffer size is 100 */

/* Global declarations */
int in_buffer[BUFSIZE];       /* processing data buffers */
int out_buffer[BUFSIZE];

/* Functions */
static int processing(int *input, int *output);
static void dataIO(void);
static long round(long a);

void main()
{
    int *input = &in_buffer[0];
    int *output = &out_buffer[0];

    puts("the 1st experiment started\n");

    /* loop forever */
    while(TRUE)
    {       
        /* 
         *  Read input data using a probe-point connected to a host file. 
         *  Write output data to a graph connected through a probe-point.
         */
        // read the input signal.
        // if the input file is sine1.dat, the signal contains 300Hz,400Hz and 500Hz.
        // if the input file is sine2.dat, the signal contains 100Hz,400Hz and 500Hz.
        // the sampling frequency is 1200Hz.
        dataIO();

        /* Remove the frequency compoment of 400Hz and 500Hz*/
    	processing(input, output);
    	
    	// write the output signal.
    	// the output file is result.dat.
    	dataIO();
    }
}

/*
 *  ======== processing ========
 *
 * FUNCTION: apply a Low-Pass FIR filter to input signal and remove the frequency higher than 350Hz.
 *
 * PARAMETERS: address of input and output buffers.
 *
 * RETURN VALUE: TRUE.
 */
 
static int processing(int *input, int *output)
{
    int i,size = BUFSIZE;
    short xx0,x,y;
      // short z[N]={0,0,0,0,0,0,0,0,0};
      short z[N]={0,0,0,0,0,0,0,0};
//short w[2*N+1]={22,356,155,990,466,220,777,216,777,26,466,9,155,0,22};
//short w[2*N+1]={6,457,56,1024,224,418,523,382,784,99,784,43,523};
// short w[2*N+1]={330*2,3299*2,1982*2,6867*2,4955*2,1594*2,6607*2,1065*2,4955*2,109*2,1982*2,17*2,330*2};
 //short w[2*N+1]={661,6598,3964,13733,9910,3187,13214,2131,9910,217,3964,34,661};
  // short w[2*N+1]={58,5628,526,8192,2105,5883,4913,3829,7369,1543,7369,504,4913,102,2105,14,526,1,58};
  //short w[2*N+1]={28,4432,280,8192,1259,4883,3356,3975,5873,1509,7048,644,5873,142,3356,30,1259,3,280,0,28};
  // short w[2*N+1]={26,651,182,1024,545,421,909,247,909,51,545,11,182,1,26};
//short w[2*N+1]={831,20846,5815,32768,17445,13486,29075,7888,29075,1647,17445,349,5815,21,831};
//short w[2*N+1]={208,5211,1454,8192,4361,3371,7269,1972,7269,412,4361,87,1454,5,208};
   short w[2*N+1]={101,4356,810,8192,2835,3403,5670,2517,7088,605,5670,193,2835,21,810};
//   short w[2*N+1]={101,4356,810,8192,2835,3403,5670,2517,7088,605,5670,193,2835,21,810,2,101};
 //  short w[2*N+1]={50,3814,454,8192,1815,3504,4235*,3084,6353,831,6353,349,4235,50,1815,8,454,0,50};
 
    long y0,z0;//22222222222222
    
    while(size--){
        xx0=*input++;
        x=xx0*6;
        z0=(long)x<<15;
        y0=0;
        
        
        for(i=0;i<N;i++)
        {
            z0-=(long)w[2*i+1]*(long)z[i];
            y0+=(long)w[2*i+2]*(long)z[i];
        }
        
        y0+=(long)w[0]*(z0>>15);
        y0=round(y0);
        
        
        for(i=N-1;i>0;i--)
        z[i]=z[i-1];
        
        z0=round(z0);
        z[0]=(short)(z0>>15);
        
        y=(short)(y0>>15);
        *output++ =y;
    }
     
    /* additional processing load */
    
  	return(TRUE);
}


/*
 *  ======== dataIO ========
 *
 * FUNCTION: read input signal and write processed output signal.
 *
 * PARAMETERS: none.
 *
 * RETURN VALUE: none.
 */
static void dataIO()
{
    /* do data I/O */
	
    return;
}

static long round(long a)
{ 
   long x3;
   x3=a&(0xffff0000);
   return x3;
}