RM0020 datasheet(28/69 Pages) STMICROELECTRONICS

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Function API

RM0020

28/69

when

N2_REALPART is defined to 1

Performance: See Section 7 and Table 40.

Example 10. fft_real_split_frac32

#include "libdsp2.h"

int 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 1/2^15 to 128/2^15 */

for (i = 0; i < 128; i++) *((short *)(inout_buffer + 64)+i) =

(short) (i+1);

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

fft_radix4_frac32_64(inout_buffer);

/* call split function to get correct FFT result divided by N */

fft_real_split_frac32(128, inout_buffer, wa_table_frac32_128,

wb_table_frac32_128);

}

6.11

Complex float windowing function

Function call:

void window_apply_complex_float(unsigned int N, float *x, float *y,

float *w);

Arguments:

Description:

Windowing function for complex float data. Input data are stored in x vector, output

data are written into y vector. The y vector can be the same as x vector (in-place

windowing).

X_Re 0

X_Re N

----





X_Re 1

X_Im 1

X_Re N

---- 1

–





X_Im

---- 1

–





Table 11.

window_apply_complex_float arguments

length of complex vectors, must be multiple of 4

x(1)

All vectors must be double word aligned. All vectors have the following memory layout:

re(0) im(0) re(1) im(1) ... re(N-1) im(N-1), where re is real part and im is imaginary part.

pointer to the input vector of length 2*N

y(1)

out

pointer to the output vector of length 2*N, y vector can be the same

as x vector (in-place windowing).

w(1)

pointer to the window vector of length 2*N

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