fft library for mbed
Dependents: 4180_Tuner mbed_capstone 4180_EditThis_copy 4180_EditThis_copy_Demo_Test
Fork of FFT by
FFT.cpp
- Committer:
- zchen78
- Date:
- 2015-04-17
- Revision:
- 1:e7e724e172dc
- Parent:
- 0:e3af07c00c13
File content as of revision 1:e7e724e172dc:
/* @file FFT.cpp @version: 1.0 @author: Suky @web www.micros-designs.com.ar @date 10/02/11 */ #include "FFT.h" // Extracted from Numerical Recipes in C void vFFT(float data[], unsigned int nn){ /*Replaces data[1..2*nn] by its discrete Fourier transform, if isign is input as 1; or replaces data[1..2*nn] by nn times its inverse discrete Fourier transform, if isign is input as -1. data is a complex array of length nn or, equivalently, a real array of length 2*nn. nn MUST be an integer power of 2 (this is not checked for!).*/ unsigned int n,mmax,m,j,istep,i; double wtemp,wr,wpr,wpi,wi,theta; float tempr,tempi; #define SWAP(a,b) tempr=(a);(a)=(b);(b)=tempr n=nn << 1; j=1; for (i=1;i<n;i+=2) { if(j>i){ SWAP(data[j],data[i]); SWAP(data[j+1],data[i+1]); } m=n >> 1; while (m >= 2 &&j>m){ j-=m; m >>= 1; } j+=m; } mmax=2; while (n > mmax) { istep=mmax << 1; theta=(6.28318530717959/mmax); wtemp=sin(0.5*theta); wpr = -2.0*wtemp*wtemp; wpi=sin(theta); wr=1.0; wi=0.0; for (m=1;m<mmax;m+=2) { for (i=m;i<=n;i+=istep) { j=i+mmax; tempr=wr*data[j]-wi*data[j+1]; tempi=wr*data[j+1]+wi*data[j]; data[j]=data[i]-tempr; data[j+1]=data[i+1]-tempi; data[i] += tempr; data[i+1] += tempi; } wr=(wtemp=wr)*wpr-wi*wpi+wr; wi=wi*wpr+wtemp*wpi+wi; } mmax=istep; } } // Extracted from Numerical Recipes in C void vRealFFT(float data[], unsigned int n){ /*Calculates the Fourier transform of a set of n real-valued data points. Replaces this data (which is stored in array data[1..n]) by the positive frequency half of its complex Fourier transform. The real-valued rst and last components of the complex transform are returned as elements data[1] and data[2], respectively. n must be a power of 2. This routine also calculates the inverse transform of a complex data array if it is the transform of real data. (Result in this case must be multiplied by 2/n.)*/ unsigned long i,i1,i2,i3,i4,np3; float c1=0.5,c2,h1r,h1i,h2r,h2i; double wr,wi,wpr,wpi,wtemp,theta; theta=3.141592653589793/(double) (n>>1); c2 = -0.5; vFFT(data,n>>1); wtemp=sin(0.5*theta); wpr = -2.0*wtemp*wtemp; wpi=sin(theta); wr=1.0+wpr; wi=wpi; np3=n+3; for (i=2;i<=(n>>2);i++) { i4=1+(i3=np3-(i2=1+(i1=i+i-1))); h1r=c1*(data[i1]+data[i3]); h1i=c1*(data[i2]-data[i4]); h2r = -c2*(data[i2]+data[i4]); h2i=c2*(data[i1]-data[i3]); data[i1]=h1r+wr*h2r-wi*h2i; data[i2]=h1i+wr*h2i+wi*h2r; data[i3]=h1r-wr*h2r+wi*h2i; data[i4] = -h1i+wr*h2i+wi*h2r; wr=(wtemp=wr)*wpr-wi*wpi+wr; wi=wi*wpr+wtemp*wpi+wi; } data[1] = (h1r=data[1])+data[2]; data[2] = h1r-data[2]; } void vCalPowerf(float Input[],float Power[], unsigned int n){ unsigned char k,j; for(k=0,j=0;k<n;k++,j+=2){ Power[k]=sqrt(Input[j]*Input[j]+Input[j+1]*Input[j+1]); } } void vCalPowerInt(float Input[],unsigned char Power[], unsigned int n){ unsigned char k,j; for(k=0,j=0;k<n;k++,j+=2){ Power[k]=sqrt(Input[j]*Input[j]+Input[j+1]*Input[j+1]); } } void vCalPowerLog(float Input[],unsigned char Power[], unsigned int n){ unsigned char k,j; float Temp; for(k=0,j=0;k<n;k++,j+=2){ if((Input[j]!=0) && (Input[j+1]!=0)){ Temp=sqrt(Input[j]*Input[j]+Input[j+1]*Input[j+1]); Power[k]=10.0*log10(Temp); }else{ Power[k]=0; } } }