Signal Processing Examples Using the TMS320C67x DSP Library (Rev. A)
http://www.ti.com/lit/an/spra947a/spra947a.pdf
3.3.4 FFT Example (Page 15)
For this example the output data is only the output image (Figure 10).
Please show how FFT was performed.
Best regards,
Daisuke
Hi Rahul,
Thank you for your reply.
I calculated the Magnitude.
/* ======================================================================= */
/* fft_sp_example.c -- FFT Example File */
/* */
/* This example demonstrates the usage of the various FFT kernels */
/* provided with the C6x DSPLIB. The example shows: */
/* - Twiddle factor generation for the various kernels */
/* - Scaling that needs to be applied to get similar output */
/* when using different kernels */
/* - Demonstrates the usage of FFT APIs */
/* */
/* Rev 0.0.1 */
/* */
/* Copyright (C) 2011 Texas Instruments Incorporated - http://www.ti.com/ */
/* */
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/* */
/* ----------------------------------------------------------------------- */
/* Copyright (c) 2011 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================= */
#include <stdint.h>
#include <math.h>
#include "../inc/dsplib.h"
/* Global definitions */
/* Number of samples for which FFT needs to be calculated */
//#define N 256
#define N 512
/* Number of unique sine waves in input data */
#define NUM_SIN_WAVES 4
/* Align the tables that we have to use */
#pragma DATA_ALIGN(x_ref, 8);
float x_ref [2*N];
#pragma DATA_ALIGN(x_sp, 8);
float x_sp [2*N];
#pragma DATA_ALIGN(y_sp, 8);
float y_sp [2*N];
#pragma DATA_ALIGN(w_sp, 8);
float w_sp [2*N];
unsigned char brev[64] = {
0x0, 0x20, 0x10, 0x30, 0x8, 0x28, 0x18, 0x38,
0x4, 0x24, 0x14, 0x34, 0xc, 0x2c, 0x1c, 0x3c,
0x2, 0x22, 0x12, 0x32, 0xa, 0x2a, 0x1a, 0x3a,
0x6, 0x26, 0x16, 0x36, 0xe, 0x2e, 0x1e, 0x3e,
0x1, 0x21, 0x11, 0x31, 0x9, 0x29, 0x19, 0x39,
0x5, 0x25, 0x15, 0x35, 0xd, 0x2d, 0x1d, 0x3d,
0x3, 0x23, 0x13, 0x33, 0xb, 0x2b, 0x1b, 0x3b,
0x7, 0x27, 0x17, 0x37, 0xf, 0x2f, 0x1f, 0x3f
};
/*
This function generates the input data and also updates the
input data arrays used by the various FFT kernels
*/
void generateInput (int numSinWaves) {
int i, j;
float sinWaveIncFreq, sinWaveMag;
/*
Based on numSinWave information, create the input data. The
input data is first created using floating point dataType. The
floating point data type is then converted to the appropriate
fixed point notation
*/
/* Clear the input floating point array */
for (i = 0; i < N; i++) {
x_ref[2*i] = (float)0.0;
x_ref[2*i+1] = (float)0.0;
}
/* Calculate the incremental freq for each sin wave */
sinWaveIncFreq = ((float)3.142)/(numSinWaves*(float)1.0);
/* Calculate the magnitude for each sin wave */
sinWaveMag = (float)1.0/(numSinWaves * (float)1.0*N);
/* Create the input array as sum of the various sin wave data */
for (j = 0; j < numSinWaves; j++) {
for (i = 0; i < N; i++) {
x_ref[2*i] += sinWaveMag * (float)cos(sinWaveIncFreq*j*i);
x_ref[2*i+1] = (float) 0.0;
}
}
/* Copy the reference input data to the various input arrays */
for (i = 0; i < N; i++) {
x_sp [2*i] = x_ref[2*i];
x_sp [2*i+1] = x_ref[2*i+1];
}
}
/*
The seperateRealImg function seperates the real and imaginary data
of the FFT output. This is needed so that the data can be plotted
using the CCS graph feature
*/
float y_real_sp [N];
float y_imag_sp [N];
seperateRealImg () {
int i, j;
for (i = 0, j = 0; j < N; i+=2, j++) {
y_real_sp[j] = y_sp[i];
y_imag_sp[j] = y_sp[i + 1];
}
}
/*
The main function that implements the example functionality.
This example demonstrates the usage of the various FFT kernels provided
with the C6x DSPLIB. The example shows:
- Twiddle factor generation for the various kernels
- Needed scaling to get correct output
- Demonstrates usage of FFT APIs
*/
/* Function for generating Specialized sequence of twiddle factors */
void gen_twiddle_fft_sp (float *w, int n)
{
int i, j, k;
double x_t, y_t, theta1, theta2, theta3;
const double PI = 3.141592654;
for (j = 1, k = 0; j <= n >> 2; j = j << 2)
{
for (i = 0; i < n >> 2; i += j)
{
theta1 = 2 * PI * i / n;
x_t = cos (theta1);
y_t = sin (theta1);
w[k] = (float) x_t;
w[k + 1] = (float) y_t;
theta2 = 4 * PI * i / n;
x_t = cos (theta2);
y_t = sin (theta2);
w[k + 2] = (float) x_t;
w[k + 3] = (float) y_t;
theta3 = 6 * PI * i / n;
x_t = cos (theta3);
y_t = sin (theta3);
w[k + 4] = (float) x_t;
w[k + 5] = (float) y_t;
k += 6;
}
}
}
#define PI ((float)3.142)
#define F1 10
#define F2 40
float y_ref[N];
void main () {
int i;
double y_pow, y_r, y_i;
/* Generate the input data */
// generateInput (NUM_SIN_WAVES);
for(i=0; i<N; i++)
{
/* real part */
x_ref[2 * i] = (sin(2 * PI * F1 * i / N) + sin(2 * PI * F2 * i / N));
/* img part */
x_ref[2 * i + 1] = 0;
}
/* Copy the reference input data to the various input arrays */
for (i = 0; i < N; i++) {
x_sp [2*i] = x_ref[2*i];
x_sp [2*i+1] = x_ref[2*i+1];
}
/* Genarate twiddle factors */
gen_twiddle_fft_sp(w_sp, N);
/* Call FFT routine */
// DSPF_sp_fftSPxSP(N, x_sp, w_sp, y_sp, brev, 4, 0, N);
DSPF_sp_fftSPxSP(N, x_sp, w_sp, y_sp, brev, 2, 0, N);
/* Call the test code to seperate the real and imaginary data */
seperateRealImg ();
/* Calculating the square root of the sum of square of the real and the imaginary part */
for(i=0; i<N; i++)
{
y_r = y_real_sp[i];
y_i = y_imag_sp[i];
y_pow = pow(y_r, y_r) - pow(y_i, y_i);
y_ref[i] = sqrt(y_pow);
}
}
/* ======================================================================== */
/* End of file: fft_example.c */
/* ------------------------------------------------------------------------ */
/* Copyright (c) 2011 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================== */
Is my calculation correct?
Best regards,
Daisuke