RM0020 datasheet(25/69 Pages) STMICROELECTRONICS

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RM0020

Function API

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Performance: See Section 7 and Table 38.

Example 9. fft_real_split_float

#include "libdsp2.h"

float inout_buffer [128+8];

/* +8 to ensure there is 32 bytes of

readable memory behind buffer */

void main(void)

{

int i;

/* example real input data, sequence from 1 to 128 */

for (i = 0; i < 128; i++) inout_buffer[i] = i+1;

/* compute complex to complex FFT of half the length */

fft_radix4_float_64(inout_buffer);

/* call split function to get correct FFT result */

fft_real_split_float(128, inout_buffer, wa_table_float_128,

wb_table_float_128);

}

6.10

Split function of N-point real to complex frac32 FFT

Function call:

void fft_real_split_frac32(unsigned int N, int *y, int *wa, int

*wb);

Arguments:

Table 10.

fft_real_split_frac32 arguments

FFT length, tested for 128, 256, 512, 1024, 2048, 4096

yin/out

pointer to the input/output vector of length N, vector must be double

word aligned

input: as input pass the output from the complex to complex frac32

FFT of half the length, data ordered x_Re(0) x_Im(0) x_Re(1)

x_Im(1)... x_Re(N/2-1) x_Im(N/2-1)

output memory layout:

X_Re(0) {0 or X_Re(N/2)} X_Re(1) X_Im(1) ... X_Re(N/2-1)

X_Im(N/2-1)

(Re - real part, Im - imaginary part)

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