fftdisplay.c

C语言DSPFFT算法

#include	"math.h"  
#include	"dsp1io.h" 
      
extern float *FFT_buff;

/************************************************************    
name:           fftdisplay                               
*************************************************************    
description:    translate FFT results output format 
                to SPC3,display, and indicator.     
*************************************************************    
prototype:      void fftdisplay(void);                                                               
*************************************************************    
reference: 		none                                             
*************************************************************    
revision history:                                                
date			content			by			version              
03MAR02			create  		tom yue		3.01                 
26JUN02			comment			tom yue		3.02                 
13JUL02			modify&comment	ZhiguoTan	3.11              
*************************************************************    
algorithm:      none
**************************************************************/  
void fftdisplay(void)
{
    unsigned *pfft,i,k,*pt,index;
    unsigned long sample_rate;  
    unsigned long sample_freq;
    float a_coef,t0,t1,*pf;
    
    
    sample_rate=dsp1in.preset & 0xfe00; 
    switch(sample_rate) {               //translate bit sign to sample_rate
	  	case FFT_F300:                       
                sample_freq=300;                    
				break;
	  	case FFT_F100: 
                sample_freq=100;                    
				break;
	  	case FFT_F30: 
                sample_freq=30;                    
				break;
	  	case FFT_F10: 
                sample_freq=10;                    
				break;
	  	case FFT_F3: 
                sample_freq=3;                    
				break; 
	  	case FFT_F1: 
                sample_freq=1;                    
				break;
		default:	
                sample_freq=600;                    
				break;
				
	}
	
    dsp1out.fftspc3.samples_freq=sample_freq;     //output samples_frequency for SPC3          
	dsp1out.fftindicator.samples_freq=sample_freq;//output samples_frequency for indicator
	dsp1out.fftdisplay.samples_freq=sample_freq;  //output samples_frequency for display

	dsp1out.fftspc3.stop_freq=sample_freq*10000/4;        //output stop frequency for SPC3 
	dsp1out.fftindicator.stop_freq=sample_freq*10000/4;   //output stop frequency for indicator       
	dsp1out.fftdisplay.stop_freq=sample_freq*10000/4;     //output stop frequency for display         

/*************************************/
/* prepare data for SPC3             */
/*************************************/
                                       
    pfft=(unsigned *)dsp1out.fftspc3.dsp1addr;
	pf=(float *)(FFT_buff+0x800);
	
	//find maximum
	t1=0.0;                             //clear t1
	index=0;
	for(i=0;i<1024;i++){
		t0=FFT_buff[i];			        //read fft results buffers
		if(t1<t0) 
		{
		    t1=t0;	            //get maximum
		    index=i;
		}
		pf[i]=t0;                       //transform integer to SPC3 buffer
	}
    dsp1out.fftspc3.ampscale=t1*10000/2048;//707.1*t1/2048;  //set amplitude scaling,units is um,RMS express
	//a_coef=10000.0/t1;                  //normalize
	a_coef = 10000.0/2048;					// do not normalize, but scaled
	for(i=0;i<1024;i++) pfft[i]=a_coef*pf[i];//transform data to SPC3 buffer

	dsp1out.fftspc3.maxAmp_freq=index*sample_freq*10000/4096;        //Frequency of the largest amplitude FFT result for SPC3 
	dsp1out.fftindicator.maxAmp_freq=index*sample_freq*10000/4096;   //Frequency of the largest amplitude FFT result indicator       
	dsp1out.fftdisplay.maxAmp_freq=index*sample_freq*10000/4096;     //Frequency of the largest amplitude FFT result display         
/*************************************/
/* prepare date for indicator        */
/*************************************/
    pt=(unsigned *)dsp1out.fftindicator.dsp1addr;
	pfft=(unsigned *)pf;                //copy upper address

	t1=0.0;                        		//set max and pointer                     
	for(i=0;i<256;i++){                 //4:1 compress data
	    t0=0.0;
	    for(k=0;k<4;k++)
	    {
	    	if(t0<FFT_buff[4*i+k]) 
	    	{
	    		t0=FFT_buff[4*i+k];    	//get the maximum of every 4 data
	    	}
	    }
		if(t1<t0) t1=t0;	            //get max
		pf[i]=t0;                       //save results
	}
    dsp1out.fftindicator.ampscale=t1*10000/2048;//707.1 * t1/2048;
                                        //set amplitude scaling
	a_coef=116.0/t1;                    //match indicator display 
	for(i=0;i<256;i++) pfft[i]=a_coef*pf[i];//normalize
	//compress byte to word by 2:1	                                    
	//one data in the  high part of int16, next data in low part of int16
	for(i=0;i<128;i++) pt[i]=(pfft[2*i]<<8)+pfft[2*i+1];

/*************************************/
/* prepare data for display          */
/*************************************/
	//for LCD 128*64, compress data 8:1
    pt=(unsigned *)dsp1out.fftdisplay.dsp1addr;
	pfft=(unsigned *)pf;                //copy this address
	
	t1=0.0;			                    //set max and pointer 
	for(i=0;i<128;i++){                 //8:1 compress data   
	    t0=0.0;
	    for(k=0;k<8;k++)
	    {
	    	if(t0<FFT_buff[8*i+k]) 
	    	{
	    		t0=FFT_buff[8*i+k];    	//get the maximum of every 8 data
	    	}
	    }
		if(t1<t0) t1=t0;	            //get max     
		pf[i]=t0;                       //save results
	}

    dsp1out.fftdisplay.ampscale=t1*10000/2048;//ampliteude scaling compress 
	a_coef=53.0/t1;                      //match LCD display
	for(i=0;i<128;i++) pfft[i]=a_coef*pf[i]; //ampliteude scaling compress
	//compress byte to word by 2:1  	
	//one data in the  high part of int16, next data in low part of int16
	for(i=0;i<64;i++) pt[i]=(pfft[2*i]<<8)+pfft[2*i+1];

	dsp1out.FFT_rem_time=0;				//inform mcu0 FFT finish
}

/****************************file end************************************/