RM0020 datasheet(14/69 Pages) STMICROELECTRONICS

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Function API

RM0020

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Example 1. bitrev_table_16bit

#include "libdsp2.h"

int inout_buffer[2*256];

void main() {

/* bit reverse permutation and calculation of 256-point FFT */

bitrev_table_16bit(16, (short *)(inout_buffer+256),

seed_radix2_16bit_256);

fft_quad_frac32(256, inout_buffer, w_table_radix2_frac32_256);}

6.2

Bit reversal permutation for 32-bit data

Function call:

void bitrev_table_32bit(unsigned int n, float *inout_buffer,

unsigned short *seed_table);

Arguments:

Table 2.

bitrev_table_32bit arguments

nin

number of groups:

for radix-2 bit reverse permutation:

n = 8 for 64 and 128-point FFT

n = 16 for 256 and 512-point FFT

n = 32 for 1024 and 2048 point FFT

n = 64 for 4096 point FFT

for radix-4 2-bit reverse permutation:

n = 4 for 64-point FFT

n = 16 for 256 and 1024-point FFT

n = 64 for 4096 point FFT

inout_buffer

in/out

pointer to the input/output vector of length 2*N, vector must be

double word aligned

memory layout:

x_Re(0) x_Im(0) x_Re(1) x_Im(1) ... x_Re(N-1) x_Im(N-1)

(Re - real part, Im - imaginary part)

seed_table

pointer to the seed table, use one of the predefined tables:

seed_radix2_32bit_64

seed_radix2_32bit_128

seed_radix2_32bit_256

seed_radix2_32bit_512

seed_radix2_32bit_1024

seed_radix2_32bit_2048

seed_radix2_32bit_4096

seed_radix4_32bit_64

seed_radix4_32bit_256

seed_radix4_32bit_1024

seed_radix4_32bit_4096

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