CCS_Programme 03: Implement DFT and IDFT usign Fixed Point Technique in Code Composer Studio

// fixed point implemention of dft and IDFT

#include <stdio.h>

#include <math.h>

#include "input32_DFT_IDFT_float.h"

#include "input32_DFT_IDFT_fixed.h"

#define N 32

#define PI (float)3.1416

#define Q15 (unsigned int)32768

#define Q14 (unsigned int)(Q15>>1)

#define Q8 (unsigned int)256

typedef struct {

float real[N];

float imag[N];

}complex;

complex xn,Xk,xc;

//Declare Structure for storing fixed point numbers

typedef struct {

int real[N];

int imag[N];

}complex_fix;

complex_fix xnn,Xkk,xcc;

float chk_real_fix_dft[N];

float chk_imag_fix_dft[N];

float chk_real_fix_idft[N];

float chk_imag_fix_idft[N];

//declare function prototype for DFT and IDFT Calculation

void dft_fix(complex_fix *g,complex_fix *G,int len);

void idft_fix(complex_fix *g,complex_fix *G,int len);

void main()

{
int n;

 //input values for DFT Calculation

for(n=0;n<N;n++)

{

xn.real[n] = x[n];

xn.imag[n] = 0;

}

//input values for DFT Calculation using Fixed point Technique

for(n=0;n<N;n++)

{

xnn.real[n] = x_fix[n];

xnn.imag[n] = 0;

}

 dft_fix(&xnn,&Xkk,N);

printf ("DFT Fixed Point done\n");

idft_fix(&xcc,&Xkk,N);

printf ("IDFT Fixed Point done\n");

}

void dft_fix(complex_fix *g,complex_fix *G,int len)

{

int n,k;

float alp,alpha,angle =0;

int cf,sf;

long prod1,prod2,sum1 = 0,sum2 = 0;

alp = (2*PI/N);

for (k=0;k<len;k++)

{

G->real[k] = 0;

G->imag[k] = 0;

alpha = alp*k;

angle = 0;

sum1 = 0;

sum2 = 0;

for(n=0;n<len;n++)

{

cf = cos(angle)*Q14; //SI1F14

sf = sin(angle)*Q14; //SI1F14

prod1 = ((long)cf*(long)g->real[n]); //SSI1F29

prod1 += ((long)sf*(long)g->imag[n]); //SSI1F29

prod1 = prod1<<1; //SI1F30

prod2 = ((long)cf*(long)g->imag[n]); //SSI1F29

prod2 -= ((long)sf*(long)g->real[n]); //SSI1F29

prod2 = prod2<<1; //SI1F30

sum1 = sum1+(prod1>>5); //SI6F25

sum2 = sum2+(prod2>>5); //SI6F25

angle = angle+alpha;

}

G->real[k] = (int)(sum1>>16); //SI6F9

chk_real_fix_dft[k] = (float)G->real[k]/(Q15>>6);

G->imag[k] = (int)(sum2>>16); //SI6F9

chk_imag_fix_dft[k] = (float)G->imag[k]/(Q15>>6);

}

}

void idft_fix(complex_fix *g,complex_fix *G,int len)

{

int n,k;

float alp,angle=0,alpha;

int cf,sf;

long prod1,prod2,sum1=0,sum2=0;

alp = (2*PI/N);

for(n=0;n<len;n++)

{

g->real[n] = 0;

g->imag[n] = 0;

alpha = alp*n;

angle = 0;

sum1 =0;

sum2 = 0;

for(k=0;k<len;k++)

{

cf = cos(angle)*Q14; //SI1F14

sf = sin(angle)*Q14; //SI1F14

prod1 = ((long)cf*(long)G->real[k]); //SSI7F23

prod1 -= ((long)sf*(long)G->imag[k]);

prod1 = prod1<<1; //SI7F24

prod2 = ((long)cf*(long)G->imag[k]);

prod2 += ((long)sf*(long)G->real[k]); //SSI7F23

prod2 = prod2<<1; //SI7F24

sum1 = sum1 + (prod1>>5); //SI12F19

sum2 = sum2 + (prod2>>5); //SI12F19

angle = angle +alpha;

}

g->real[n] = (int)(sum1>>16); //SI7F8

chk_real_fix_idft[n] = (float)g->real[n]/(Q15>>7); //for testing CCS calculating with MATLAB Calculation

g->imag[n] = (int)(sum2>>16);

chk_imag_fix_idft[n] = (float)g->imag[n]/(Q15>>7); //for testing CCS calculation with MATLAB Calculation

}

}