/* ======================================================================== */
/* TEXAS INSTRUMENTS, INC. */
/* */
/* DSPLIB DSP Signal Processing Library */
/* */
/* Release: Version 1.02 */
/* CVS Revision: 1.3 Fri Mar 22 02:08:27 2002 (UTC) */
/* Snapshot date: 18-Apr-2002 */
/* */
/* This library contains proprietary intellectual property of Texas */
/* Instruments, Inc. The library and its source code are protected by */
/* various copyrights, and portions may also be protected by patents or */
/* other legal protections. */
/* */
/* This software is licensed for use with Texas Instruments TMS320 */
/* family DSPs. This license was provided to you prior to installing */
/* the software. You may review this license by consulting the file */
/* TI_license.PDF which accompanies the files in this library. */
/* ------------------------------------------------------------------------ */
/* Copyright (C) 2002 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================== */
/* ======================================================================== */
/* */
/* TEXAS INSTRUMENTS, INC. */
/* */
/* NAME */
/* DSP_radix2 -- In-place Radix-2 FFT (Little Endian) */
/* */
/* REVISION DATE */
/* 10-Dec-2001 */
/* */
/* USAGE */
/* This routine is C-callable and can be called as: */
/* */
/* void DSP_radix2(int n, short *restrict xy, */
/* const short *restrict w); */
/* */
/* n -- FFT size (input) */
/* xy[] -- input and output sequences (dim-n) (input/output) */
/* w[] -- FFT coefficients (dim-n/2) (input) */
/* */
/* DESCRIPTION */
/* This routine is used to compute FFT of a complex sequece of size */
/* n, a power of 2, with "decimation-in-frequency decomposition" */
/* method, ie, the output is in bit-reversed order. Each complex */
/* value is with interleaved 16-bit real and imaginary parts. To */
/* prevent overflow, input samples may have to be scaled by 1/n. */
/* */
/* void DSP_radix2(int n, short *restrict xy, */
/* const short *restrict w) */
/* { */
/* short n1,n2,ie,ia,i,j,k,l; */
/* short xt,yt,c,s; */
/* */
/* n2 = n; */
/* ie = 1; */
/* for (k=n; k > 1; k = (k >> 1) ) */
/* { */
/* n1 = n2; */
/* n2 = n2>>1; */
/* ia = 0; */
/* for (j=0; j < n2; j++) */
/* { */
/* c = w[2*ia]; */
/* s = w[2*ia+1]; */
/* ia = ia + ie; */
/* for (i=j; i < n; i += n1) */
/* { */
/* l = i + n2; */
/* xt = xy[2*l] - xy[2*i]; */
/* xy[2*i] = xy[2*i] + xy[2*l]; */
/* yt = xy[2*l+1] - xy[2*i+1]; */
/* xy[2*i+1] = xy[2*i+1] + xy[2*l+1]; */
/* xy[2*l] = (c*xt + s*yt)>>15; */
/* xy[2*l+1] = (c*yt - s*xt)>>15; */
/* } */
/* } */
/* ie = ie<<1; */
/* } */
/* } */
/* */
/* ASSUMPTIONS */
/* 16 <= n <= 32768 */
/* Both input xy and coefficient w must be aligned on word boundary. */
/* w coef stored ordered is k*(-cos[0*delta]), k*(-sin[0*delta]), */
/* k*(-cos[1*delta]), ... where delta = 2*PI/N, k = 32767 */
/* Assembly code is written for processor in Little Endian mode */
/* Input xy and coefficients w are 16 bit data. */
/* */
/* MEMORY NOTE */
/* Align xy and w on different word boundaries to minimize */
/* memory bank hits. */
/* */
/* TECHNIQUES */
/* 1. Loading input xy as well as coefficient w in word. */
/* 2. Both loops j and i shown in the C code are placed in the */
/* INNERLOOP of the assembly code. */
/* */
/* CYCLES */
/* cycles = log2(N) * (4*N/2+7) + 34 + N/4. */
/* */
/* (The N/4 term is due to bank conflicts that occur when xy and w */
/* are aligned as suggested above, under "MEMORY NOTE.") */
/* */
/* For N = 256, cycles = 4250. */
/* */
/* CODESIZE */
/* 800 bytes */
/* */
/* ------------------------------------------------------------------------ */
/* Copyright (c) 2002 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================== */
#ifndef DSP_RADIX2_H_
#define DSP_RADIX2_H_ 1
void DSP_radix2(int n, short *restrict xy,
const short *restrict w);
#endif
/* ======================================================================== */
/* End of file: dsp_radix2.h */
/* ------------------------------------------------------------------------ */
/* Copyright (c) 2002 Texas Instruments, Incorporated. */
/* All Rights Reserved. */
/* ======================================================================== */