firfft.c

C语言DSPFFT算法

/************************************************************
name:           PD25XY-fftdisplay.c
description:    If FFT is completed then return 0, else return fft buf index.
prototype:      void firfft(float temp)                                       
call:          	firfft(temp)                                       
                                                          
position:       dsp1.mak                                  
version:        1.0             date:   2001-12-19        
author:         tom yue         date:   2001-12-19        
check:          tom yue         date:       
approval:  
remark:         The input is processed at following procedure:
					1,filter (multirate multistage fir);
					2,buffer the filtered data and window it
					3,transform the windowed data to frequence domain                                     
***********************************************************
history
date:23JUN02				by:		TZG
update:	add	comment		
***********************************************************/

#include	"math.h"  
#include	"regs54xx.h" 
#include	"dsp1io.h" 

#include "fir.h"
#include "fft.h"


void	hamming_win_proc0(
float 	*x,	/* the data which will be windowed */
int 	n, 	/* the number of the data which will be windowed */
float	tx  /* hamming window coefficient */);

extern float *FFT_buff;
extern int FFT_buf_counter;

unsigned firfft(float temp)
{
 	float t0;                           //remain time for FFT
    unsigned ui;                        //corrently selected FFT rate
    static unsigned ysample_rate=0;     //past selected FFT rate
    unsigned f0;                        //sample frequent
  
    /* if the FFT stop command is 1, then do nothing but return 1 */
    if(dsp1in.preset & CMD_FFTSTP) {
       	dsp1out.FFT_rem_time |=1;
    	FFT_buf_counter=0;
    	return 1;
    }
	
	/* get the FFT rate*/
	ui=dsp1in.preset; ui &=0xfe00;		//if the desired filter has been changed,
	if(ysample_rate !=ui){				//initialize the filter-and-FFT system.
    	initial_filter();
    	FFT_buf_counter=0;
    	ysample_rate=ui;
    }

//test function
/*	static long n=0;
	temp=sin(0.031415926*n);
	n++;
*/
	
	/* according to different FFT rate, do corresponding fir */
    switch(ysample_rate){
  		case FFT_F300:
  				fir(5,temp);
    			f0=300;
    			break;
  		case FFT_F100:
  				fir(4,temp);
    			f0=100;
    			break;  
  		case FFT_F30:
  				fir(3,temp);
    			f0=30;
   			break;  
  		case FFT_F10:
  				fir(2,temp);
    			f0=10;
    			break;  
  		case FFT_F3:
  				fir(1,temp);
    			f0=3;
    			break;  
  		case FFT_F1:
  				fir(0,temp);
    			f0=1;
	   			break;     
    	default:
  				fir(6,temp);
    			f0=600;
    			break;
    }
	
	/* compute the remain time for FFT */
    t0=(4096-FFT_buf_counter);t0 /=f0; t0+=1; 
    if(t0>4096/f0) t0=0;
	dsp1out.FFT_rem_time=t0;
	


	
    /* if the buffer is not full,then return the current index of buffer*/
    if(FFT_buf_counter<4096) return FFT_buf_counter+1;        
    
//test function
/*	int i;  
	for(i=0;i<4096;i++)
	{
		FFT_buff[i]=2*sin(0.1*i);
	}
	FFT_buf_counter=4096;	    
*/
	/* according to different FFT rate, add corresponding window */
//	hamming_win_proc0(FFT_buff,4096,1);
	
	/* compute the FFT */
	fft(FFT_buff,4096);  
	int k;
	for(k=0;k<4;k++)
	{
		FFT_buff[k]=0.0;
	}
	FFT_buf_counter=0;                 
	return 0;
}