arm_cfft_radix4_f32.c
1236 lines
| 34.4 KiB
| text/x-c
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CLexer
r71 | /* ---------------------------------------------------------------------- | |||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 15. July 2011 | ||||
* $Revision: V1.0.10 | ||||
* | ||||
* Project: CMSIS DSP Library | ||||
* Title: arm_cfft_radix4_f32.c | ||||
* | ||||
* Description: Radix-4 Decimation in Frequency CFFT & CIFFT Floating point processing function | ||||
* | ||||
* | ||||
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | ||||
* | ||||
* Version 1.0.10 2011/7/15 | ||||
* Big Endian support added and Merged M0 and M3/M4 Source code. | ||||
* | ||||
* Version 1.0.3 2010/11/29 | ||||
* Re-organized the CMSIS folders and updated documentation. | ||||
* | ||||
* Version 1.0.2 2010/11/11 | ||||
* Documentation updated. | ||||
* | ||||
* Version 1.0.1 2010/10/05 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 1.0.0 2010/09/20 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 0.0.5 2010/04/26 | ||||
* incorporated review comments and updated with latest CMSIS layer | ||||
* | ||||
* Version 0.0.3 2010/03/10 | ||||
* Initial version | ||||
* -------------------------------------------------------------------- */ | ||||
#include "arm_math.h" | ||||
/** | ||||
* @ingroup groupTransforms | ||||
*/ | ||||
/** | ||||
* @defgroup CFFT_CIFFT Complex FFT Functions | ||||
* | ||||
* \par | ||||
* Complex Fast Fourier Transform(CFFT) and Complex Inverse Fast Fourier Transform(CIFFT) is an efficient algorithm to compute Discrete Fourier Transform(DFT) and Inverse Discrete Fourier Transform(IDFT). | ||||
* Computational complexity of CFFT reduces drastically when compared to DFT. | ||||
* \par | ||||
* This set of functions implements CFFT/CIFFT | ||||
* for Q15, Q31, and floating-point data types. The functions operates on in-place buffer which uses same buffer for input and output. | ||||
* Complex input is stored in input buffer in an interleaved fashion. | ||||
* | ||||
* \par | ||||
* The functions operate on blocks of input and output data and each call to the function processes | ||||
* <code>2*fftLen</code> samples through the transform. <code>pSrc</code> points to In-place arrays containing <code>2*fftLen</code> values. | ||||
* \par | ||||
* The <code>pSrc</code> points to the array of in-place buffer of size <code>2*fftLen</code> and inputs and outputs are stored in an interleaved fashion as shown below. | ||||
* <pre> {real[0], imag[0], real[1], imag[1],..} </pre> | ||||
* | ||||
* \par Lengths supported by the transform: | ||||
* \par | ||||
* Internally, the function utilize a radix-4 decimation in frequency(DIF) algorithm | ||||
* and the size of the FFT supported are of the lengths [16, 64, 256, 1024]. | ||||
* | ||||
* | ||||
* \par Algorithm: | ||||
* | ||||
* <b>Complex Fast Fourier Transform:</b> | ||||
* \par | ||||
* Input real and imaginary data: | ||||
* <pre> | ||||
* x(n) = xa + j * ya | ||||
* x(n+N/4 ) = xb + j * yb | ||||
* x(n+N/2 ) = xc + j * yc | ||||
* x(n+3N 4) = xd + j * yd | ||||
* </pre> | ||||
* where N is length of FFT | ||||
* \par | ||||
* Output real and imaginary data: | ||||
* <pre> | ||||
* X(4r) = xa'+ j * ya' | ||||
* X(4r+1) = xb'+ j * yb' | ||||
* X(4r+2) = xc'+ j * yc' | ||||
* X(4r+3) = xd'+ j * yd' | ||||
* </pre> | ||||
* \par | ||||
* Twiddle factors for radix-4 FFT: | ||||
* <pre> | ||||
* Wn = co1 + j * (- si1) | ||||
* W2n = co2 + j * (- si2) | ||||
* W3n = co3 + j * (- si3) | ||||
* </pre> | ||||
* | ||||
* \par | ||||
* \image html CFFT.gif "Radix-4 Decimation-in Frequency Complex Fast Fourier Transform" | ||||
* | ||||
* \par | ||||
* Output from Radix-4 CFFT Results in Digit reversal order. Interchange middle two branches of every butterfly results in Bit reversed output. | ||||
* \par | ||||
* <b> Butterfly CFFT equations:</b> | ||||
* <pre> | ||||
* xa' = xa + xb + xc + xd | ||||
* ya' = ya + yb + yc + yd | ||||
* xc' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) | ||||
* yc' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) | ||||
* xb' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) | ||||
* yb' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) | ||||
* xd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) | ||||
* yd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) | ||||
* </pre> | ||||
* | ||||
* | ||||
* <b>Complex Inverse Fast Fourier Transform:</b> | ||||
* \par | ||||
* CIFFT uses same twiddle factor table as CFFT with modifications in the design equation as shown below. | ||||
* | ||||
* \par | ||||
* <b> Modified Butterfly CIFFT equations:</b> | ||||
* <pre> | ||||
* xa' = xa + xb + xc + xd | ||||
* ya' = ya + yb + yc + yd | ||||
* xc' = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) | ||||
* yc' = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) | ||||
* xb' = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) | ||||
* yb' = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) | ||||
* xd' = (xa+yb-xc-yd)* co3 - (ya-xb-yc+xd)* (si3) | ||||
* yd' = (ya-xb-yc+xd)* co3 + (xa+yb-xc-yd)* (si3) | ||||
* </pre> | ||||
* | ||||
* \par Instance Structure | ||||
* A separate instance structure must be defined for each Instance but the twiddle factors and bit reversal tables can be reused. | ||||
* There are separate instance structure declarations for each of the 3 supported data types. | ||||
* | ||||
* \par Initialization Functions | ||||
* There is also an associated initialization function for each data type. | ||||
* The initialization function performs the following operations: | ||||
* - Sets the values of the internal structure fields. | ||||
* - Initializes twiddle factor table and bit reversal table pointers | ||||
* \par | ||||
* Use of the initialization function is optional. | ||||
* However, if the initialization function is used, then the instance structure cannot be placed into a const data section. | ||||
* To place an instance structure into a const data section, the instance structure must be manually initialized. | ||||
* Manually initialize the instance structure as follows: | ||||
* <pre> | ||||
*arm_cfft_radix4_instance_f32 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor, onebyfftLen}; | ||||
*arm_cfft_radix4_instance_q31 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor}; | ||||
*arm_cfft_radix4_instance_q15 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor}; | ||||
* </pre> | ||||
* \par | ||||
* where <code>fftLen</code> length of CFFT/CIFFT; <code>ifftFlag</code> Flag for selection of CFFT or CIFFT(Set ifftFlag to calculate CIFFT otherwise calculates CFFT); | ||||
* <code>bitReverseFlag</code> Flag for selection of output order(Set bitReverseFlag to output in normal order otherwise output in bit reversed order); | ||||
* <code>pTwiddle</code>points to array of twiddle coefficients; <code>pBitRevTable</code> points to the array of bit reversal table. | ||||
* <code>twidCoefModifier</code> modifier for twiddle factor table which supports all FFT lengths with same table; | ||||
* <code>pBitRevTable</code> modifier for bit reversal table which supports all FFT lengths with same table. | ||||
* <code>onebyfftLen</code> value of 1/fftLen to calculate CIFFT; | ||||
* | ||||
* \par Fixed-Point Behavior | ||||
* Care must be taken when using the fixed-point versions of the CFFT/CIFFT function. | ||||
* Refer to the function specific documentation below for usage guidelines. | ||||
*/ | ||||
/** | ||||
* @addtogroup CFFT_CIFFT | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @details | ||||
* @brief Processing function for the floating-point CFFT/CIFFT. | ||||
* @param[in] *S points to an instance of the floating-point CFFT/CIFFT structure. | ||||
* @param[in, out] *pSrc points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place. | ||||
* @return none. | ||||
*/ | ||||
void arm_cfft_radix4_f32( | ||||
const arm_cfft_radix4_instance_f32 * S, | ||||
float32_t * pSrc) | ||||
{ | ||||
if(S->ifftFlag == 1u) | ||||
{ | ||||
/* Complex IFFT radix-4 */ | ||||
arm_radix4_butterfly_inverse_f32(pSrc, S->fftLen, S->pTwiddle, | ||||
S->twidCoefModifier, S->onebyfftLen); | ||||
} | ||||
else | ||||
{ | ||||
/* Complex FFT radix-4 */ | ||||
arm_radix4_butterfly_f32(pSrc, S->fftLen, S->pTwiddle, | ||||
S->twidCoefModifier); | ||||
} | ||||
if(S->bitReverseFlag == 1u) | ||||
{ | ||||
/* Bit Reversal */ | ||||
arm_bitreversal_f32(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable); | ||||
} | ||||
} | ||||
/** | ||||
* @} end of CFFT_CIFFT group | ||||
*/ | ||||
/* ---------------------------------------------------------------------- | ||||
** Internal helper function used by the FFTs | ||||
** ------------------------------------------------------------------- */ | ||||
/* | ||||
* @brief Core function for the floating-point CFFT butterfly process. | ||||
* @param[in, out] *pSrc points to the in-place buffer of floating-point data type. | ||||
* @param[in] fftLen length of the FFT. | ||||
* @param[in] *pCoef points to the twiddle coefficient buffer. | ||||
* @param[in] twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table. | ||||
* @return none. | ||||
*/ | ||||
void arm_radix4_butterfly_f32( | ||||
float32_t * pSrc, | ||||
uint16_t fftLen, | ||||
float32_t * pCoef, | ||||
uint16_t twidCoefModifier) | ||||
{ | ||||
float32_t co1, co2, co3, si1, si2, si3; | ||||
float32_t t1, t2, r1, r2, s1, s2; | ||||
uint32_t ia1, ia2, ia3; | ||||
uint32_t i0, i1, i2, i3; | ||||
uint32_t n1, n2, j, k; | ||||
#ifndef ARM_MATH_CM0 | ||||
/* Run the below code for Cortex-M4 and Cortex-M3 */ | ||||
/* Initializations for the first stage */ | ||||
n2 = fftLen; | ||||
n1 = n2; | ||||
/* n2 = fftLen/4 */ | ||||
n2 >>= 2u; | ||||
i0 = 0u; | ||||
ia1 = 0u; | ||||
j = n2; | ||||
/* Calculation of first stage */ | ||||
do | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* Butterfly implementation */ | ||||
/* xa + xc */ | ||||
r1 = pSrc[(2u * i0)] + pSrc[(2u * i2)]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[2u * i0] - pSrc[2u * i2]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xb + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = r1 + t1; | ||||
/* (xa + xc) - (xb + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = s1 + t2; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* yb - yd */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* xb - xd */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* index calculation for the coefficients */ | ||||
ia2 = ia1 + ia1; | ||||
co2 = pCoef[ia2 * 2u]; | ||||
si2 = pCoef[(ia2 * 2u) + 1u]; | ||||
/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = (r1 * co2) + (s1 * si2); | ||||
/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = (s1 * co2) - (r1 * si2); | ||||
/* (xa - xc) + (yb - yd) */ | ||||
r1 = r2 + t1; | ||||
/* (xa - xc) - (yb - yd) */ | ||||
r2 = r2 - t1; | ||||
/* (ya - yc) - (xb - xd) */ | ||||
s1 = s2 - t2; | ||||
/* (ya - yc) + (xb - xd) */ | ||||
s2 = s2 + t2; | ||||
co1 = pCoef[ia1 * 2u]; | ||||
si1 = pCoef[(ia1 * 2u) + 1u]; | ||||
/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = (r1 * co1) + (s1 * si1); | ||||
/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = (s1 * co1) - (r1 * si1); | ||||
/* index calculation for the coefficients */ | ||||
ia3 = ia2 + ia1; | ||||
co3 = pCoef[ia3 * 2u]; | ||||
si3 = pCoef[(ia3 * 2u) + 1u]; | ||||
/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = (r2 * co3) + (s2 * si3); | ||||
/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = (s2 * co3) - (r2 * si3); | ||||
/* Twiddle coefficients index modifier */ | ||||
ia1 = ia1 + twidCoefModifier; | ||||
/* Updating input index */ | ||||
i0 = i0 + 1u; | ||||
} | ||||
while(--j); | ||||
twidCoefModifier <<= 2u; | ||||
/* Calculation of second stage to excluding last stage */ | ||||
for (k = fftLen / 4; k > 4u; k >>= 2u) | ||||
{ | ||||
/* Initializations for the first stage */ | ||||
n1 = n2; | ||||
n2 >>= 2u; | ||||
ia1 = 0u; | ||||
/* Calculation of first stage */ | ||||
for (j = 0u; j <= (n2 - 1u); j++) | ||||
{ | ||||
/* index calculation for the coefficients */ | ||||
ia2 = ia1 + ia1; | ||||
ia3 = ia2 + ia1; | ||||
co1 = pCoef[ia1 * 2u]; | ||||
si1 = pCoef[(ia1 * 2u) + 1u]; | ||||
co2 = pCoef[ia2 * 2u]; | ||||
si2 = pCoef[(ia2 * 2u) + 1u]; | ||||
co3 = pCoef[ia3 * 2u]; | ||||
si3 = pCoef[(ia3 * 2u) + 1u]; | ||||
/* Twiddle coefficients index modifier */ | ||||
ia1 = ia1 + twidCoefModifier; | ||||
for (i0 = j; i0 < fftLen; i0 += n1) | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* xa + xc */ | ||||
r1 = pSrc[(2u * i0)] + pSrc[(2u * i2)]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[(2u * i0)] - pSrc[(2u * i2)]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xb + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = r1 + t1; | ||||
/* xa + xc -(xb + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = s1 + t2; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* (yb - yd) */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* (xb - xd) */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = (r1 * co2) + (s1 * si2); | ||||
/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = (s1 * co2) - (r1 * si2); | ||||
/* (xa - xc) + (yb - yd) */ | ||||
r1 = r2 + t1; | ||||
/* (xa - xc) - (yb - yd) */ | ||||
r2 = r2 - t1; | ||||
/* (ya - yc) - (xb - xd) */ | ||||
s1 = s2 - t2; | ||||
/* (ya - yc) + (xb - xd) */ | ||||
s2 = s2 + t2; | ||||
/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = (r1 * co1) + (s1 * si1); | ||||
/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = (s1 * co1) - (r1 * si1); | ||||
/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = (r2 * co3) + (s2 * si3); | ||||
/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = (s2 * co3) - (r2 * si3); | ||||
} | ||||
} | ||||
twidCoefModifier <<= 2u; | ||||
} | ||||
/* Initializations of last stage */ | ||||
n1 = n2; | ||||
n2 >>= 2u; | ||||
/* Calculations of last stage */ | ||||
for (i0 = 0u; i0 <= (fftLen - n1); i0 += n1) | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* Butterfly implementation */ | ||||
/* xa + xb */ | ||||
r1 = pSrc[2u * i0] + pSrc[2u * i2]; | ||||
/* xa - xb */ | ||||
r2 = pSrc[2u * i0] - pSrc[2u * i2]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xc + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = r1 + t1; | ||||
/* (xa + xb) - (xc + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = s1 + t2; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* (yb-yd) */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* (xb-xd) */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = r1; | ||||
/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = s1; | ||||
/* (xa+yb-xc-yd) */ | ||||
r1 = r2 + t1; | ||||
/* (xa-yb-xc+yd) */ | ||||
r2 = r2 - t1; | ||||
/* (ya-xb-yc+xd) */ | ||||
s1 = s2 - t2; | ||||
/* (ya+xb-yc-xd) */ | ||||
s2 = s2 + t2; | ||||
/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = r1; | ||||
/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = s1; | ||||
/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = r2; | ||||
/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = s2; | ||||
} | ||||
#else | ||||
/* Run the below code for Cortex-M0 */ | ||||
/* Initializations for the fft calculation */ | ||||
n2 = fftLen; | ||||
n1 = n2; | ||||
for (k = fftLen; k > 1u; k >>= 2u) | ||||
{ | ||||
/* Initializations for the fft calculation */ | ||||
n1 = n2; | ||||
n2 >>= 2u; | ||||
ia1 = 0u; | ||||
/* FFT Calculation */ | ||||
for (j = 0u; j <= (n2 - 1u); j++) | ||||
{ | ||||
/* index calculation for the coefficients */ | ||||
ia2 = ia1 + ia1; | ||||
ia3 = ia2 + ia1; | ||||
co1 = pCoef[ia1 * 2u]; | ||||
si1 = pCoef[(ia1 * 2u) + 1u]; | ||||
co2 = pCoef[ia2 * 2u]; | ||||
si2 = pCoef[(ia2 * 2u) + 1u]; | ||||
co3 = pCoef[ia3 * 2u]; | ||||
si3 = pCoef[(ia3 * 2u) + 1u]; | ||||
/* Twiddle coefficients index modifier */ | ||||
ia1 = ia1 + twidCoefModifier; | ||||
for (i0 = j; i0 < fftLen; i0 += n1) | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* xa + xc */ | ||||
r1 = pSrc[(2u * i0)] + pSrc[(2u * i2)]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[(2u * i0)] - pSrc[(2u * i2)]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xb + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = r1 + t1; | ||||
/* xa + xc -(xb + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = s1 + t2; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* (yb - yd) */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* (xb - xd) */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = (r1 * co2) + (s1 * si2); | ||||
/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = (s1 * co2) - (r1 * si2); | ||||
/* (xa - xc) + (yb - yd) */ | ||||
r1 = r2 + t1; | ||||
/* (xa - xc) - (yb - yd) */ | ||||
r2 = r2 - t1; | ||||
/* (ya - yc) - (xb - xd) */ | ||||
s1 = s2 - t2; | ||||
/* (ya - yc) + (xb - xd) */ | ||||
s2 = s2 + t2; | ||||
/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = (r1 * co1) + (s1 * si1); | ||||
/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = (s1 * co1) - (r1 * si1); | ||||
/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = (r2 * co3) + (s2 * si3); | ||||
/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = (s2 * co3) - (r2 * si3); | ||||
} | ||||
} | ||||
twidCoefModifier <<= 2u; | ||||
} | ||||
#endif /* #ifndef ARM_MATH_CM0 */ | ||||
} | ||||
/* | ||||
* @brief Core function for the floating-point CIFFT butterfly process. | ||||
* @param[in, out] *pSrc points to the in-place buffer of floating-point data type. | ||||
* @param[in] fftLen length of the FFT. | ||||
* @param[in] *pCoef points to twiddle coefficient buffer. | ||||
* @param[in] twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table. | ||||
* @param[in] onebyfftLen value of 1/fftLen. | ||||
* @return none. | ||||
*/ | ||||
void arm_radix4_butterfly_inverse_f32( | ||||
float32_t * pSrc, | ||||
uint16_t fftLen, | ||||
float32_t * pCoef, | ||||
uint16_t twidCoefModifier, | ||||
float32_t onebyfftLen) | ||||
{ | ||||
float32_t co1, co2, co3, si1, si2, si3; | ||||
float32_t t1, t2, r1, r2, s1, s2; | ||||
uint32_t ia1, ia2, ia3; | ||||
uint32_t i0, i1, i2, i3; | ||||
uint32_t n1, n2, j, k; | ||||
#ifndef ARM_MATH_CM0 | ||||
/* Run the below code for Cortex-M4 and Cortex-M3 */ | ||||
/* Initializations for the first stage */ | ||||
n2 = fftLen; | ||||
n1 = n2; | ||||
/* n2 = fftLen/4 */ | ||||
n2 >>= 2u; | ||||
i0 = 0u; | ||||
ia1 = 0u; | ||||
j = n2; | ||||
/* Calculation of first stage */ | ||||
do | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* Butterfly implementation */ | ||||
/* xa + xc */ | ||||
r1 = pSrc[(2u * i0)] + pSrc[(2u * i2)]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[2u * i0] - pSrc[2u * i2]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xb + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = r1 + t1; | ||||
/* (xa + xc) - (xb + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = s1 + t2; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* yb - yd */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* xb - xd */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* index calculation for the coefficients */ | ||||
ia2 = ia1 + ia1; | ||||
co2 = pCoef[ia2 * 2u]; | ||||
si2 = pCoef[(ia2 * 2u) + 1u]; | ||||
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = (r1 * co2) - (s1 * si2); | ||||
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = (s1 * co2) + (r1 * si2); | ||||
/* (xa - xc) - (yb - yd) */ | ||||
r1 = r2 - t1; | ||||
/* (xa - xc) + (yb - yd) */ | ||||
r2 = r2 + t1; | ||||
/* (ya - yc) + (xb - xd) */ | ||||
s1 = s2 + t2; | ||||
/* (ya - yc) - (xb - xd) */ | ||||
s2 = s2 - t2; | ||||
co1 = pCoef[ia1 * 2u]; | ||||
si1 = pCoef[(ia1 * 2u) + 1u]; | ||||
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = (r1 * co1) - (s1 * si1); | ||||
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = (s1 * co1) + (r1 * si1); | ||||
/* index calculation for the coefficients */ | ||||
ia3 = ia2 + ia1; | ||||
co3 = pCoef[ia3 * 2u]; | ||||
si3 = pCoef[(ia3 * 2u) + 1u]; | ||||
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = (r2 * co3) - (s2 * si3); | ||||
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = (s2 * co3) + (r2 * si3); | ||||
/* Twiddle coefficients index modifier */ | ||||
ia1 = ia1 + twidCoefModifier; | ||||
/* Updating input index */ | ||||
i0 = i0 + 1u; | ||||
} | ||||
while(--j); | ||||
twidCoefModifier <<= 2u; | ||||
/* Calculation of second stage to excluding last stage */ | ||||
for (k = fftLen / 4; k > 4u; k >>= 2u) | ||||
{ | ||||
/* Initializations for the first stage */ | ||||
n1 = n2; | ||||
n2 >>= 2u; | ||||
ia1 = 0u; | ||||
/* Calculation of first stage */ | ||||
for (j = 0u; j <= (n2 - 1u); j++) | ||||
{ | ||||
/* index calculation for the coefficients */ | ||||
ia2 = ia1 + ia1; | ||||
ia3 = ia2 + ia1; | ||||
co1 = pCoef[ia1 * 2u]; | ||||
si1 = pCoef[(ia1 * 2u) + 1u]; | ||||
co2 = pCoef[ia2 * 2u]; | ||||
si2 = pCoef[(ia2 * 2u) + 1u]; | ||||
co3 = pCoef[ia3 * 2u]; | ||||
si3 = pCoef[(ia3 * 2u) + 1u]; | ||||
/* Twiddle coefficients index modifier */ | ||||
ia1 = ia1 + twidCoefModifier; | ||||
for (i0 = j; i0 < fftLen; i0 += n1) | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* xa + xc */ | ||||
r1 = pSrc[(2u * i0)] + pSrc[(2u * i2)]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[(2u * i0)] - pSrc[(2u * i2)]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xb + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = r1 + t1; | ||||
/* xa + xc -(xb + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = s1 + t2; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* (yb - yd) */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* (xb - xd) */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = (r1 * co2) - (s1 * si2); | ||||
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = (s1 * co2) + (r1 * si2); | ||||
/* (xa - xc) - (yb - yd) */ | ||||
r1 = r2 - t1; | ||||
/* (xa - xc) + (yb - yd) */ | ||||
r2 = r2 + t1; | ||||
/* (ya - yc) + (xb - xd) */ | ||||
s1 = s2 + t2; | ||||
/* (ya - yc) - (xb - xd) */ | ||||
s2 = s2 - t2; | ||||
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = (r1 * co1) - (s1 * si1); | ||||
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = (s1 * co1) + (r1 * si1); | ||||
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = (r2 * co3) - (s2 * si3); | ||||
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = (s2 * co3) + (r2 * si3); | ||||
} | ||||
} | ||||
twidCoefModifier <<= 2u; | ||||
} | ||||
/* Initializations of last stage */ | ||||
n1 = n2; | ||||
n2 >>= 2u; | ||||
/* Calculations of last stage */ | ||||
for (i0 = 0u; i0 <= (fftLen - n1); i0 += n1) | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* Butterfly implementation */ | ||||
/* xa + xc */ | ||||
r1 = pSrc[2u * i0] + pSrc[2u * i2]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[2u * i0] - pSrc[2u * i2]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xc + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = (r1 + t1) * onebyfftLen; | ||||
/* (xa + xb) - (xc + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = (s1 + t2) * onebyfftLen; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* (yb-yd) */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* (xb-xd) */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = r1 * onebyfftLen; | ||||
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = s1 * onebyfftLen; | ||||
/* (xa - xc) - (yb-yd) */ | ||||
r1 = r2 - t1; | ||||
/* (xa - xc) + (yb-yd) */ | ||||
r2 = r2 + t1; | ||||
/* (ya - yc) + (xb-xd) */ | ||||
s1 = s2 + t2; | ||||
/* (ya - yc) - (xb-xd) */ | ||||
s2 = s2 - t2; | ||||
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = r1 * onebyfftLen; | ||||
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = s1 * onebyfftLen; | ||||
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = r2 * onebyfftLen; | ||||
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = s2 * onebyfftLen; | ||||
} | ||||
#else | ||||
/* Run the below code for Cortex-M0 */ | ||||
/* Initializations for the first stage */ | ||||
n2 = fftLen; | ||||
n1 = n2; | ||||
/* Calculation of first stage */ | ||||
for (k = fftLen; k > 4u; k >>= 2u) | ||||
{ | ||||
/* Initializations for the first stage */ | ||||
n1 = n2; | ||||
n2 >>= 2u; | ||||
ia1 = 0u; | ||||
/* Calculation of first stage */ | ||||
for (j = 0u; j <= (n2 - 1u); j++) | ||||
{ | ||||
/* index calculation for the coefficients */ | ||||
ia2 = ia1 + ia1; | ||||
ia3 = ia2 + ia1; | ||||
co1 = pCoef[ia1 * 2u]; | ||||
si1 = pCoef[(ia1 * 2u) + 1u]; | ||||
co2 = pCoef[ia2 * 2u]; | ||||
si2 = pCoef[(ia2 * 2u) + 1u]; | ||||
co3 = pCoef[ia3 * 2u]; | ||||
si3 = pCoef[(ia3 * 2u) + 1u]; | ||||
/* Twiddle coefficients index modifier */ | ||||
ia1 = ia1 + twidCoefModifier; | ||||
for (i0 = j; i0 < fftLen; i0 += n1) | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* xa + xc */ | ||||
r1 = pSrc[(2u * i0)] + pSrc[(2u * i2)]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[(2u * i0)] - pSrc[(2u * i2)]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xb + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = r1 + t1; | ||||
/* xa + xc -(xb + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = s1 + t2; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* (yb - yd) */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* (xb - xd) */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = (r1 * co2) - (s1 * si2); | ||||
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = (s1 * co2) + (r1 * si2); | ||||
/* (xa - xc) - (yb - yd) */ | ||||
r1 = r2 - t1; | ||||
/* (xa - xc) + (yb - yd) */ | ||||
r2 = r2 + t1; | ||||
/* (ya - yc) + (xb - xd) */ | ||||
s1 = s2 + t2; | ||||
/* (ya - yc) - (xb - xd) */ | ||||
s2 = s2 - t2; | ||||
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = (r1 * co1) - (s1 * si1); | ||||
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = (s1 * co1) + (r1 * si1); | ||||
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = (r2 * co3) - (s2 * si3); | ||||
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = (s2 * co3) + (r2 * si3); | ||||
} | ||||
} | ||||
twidCoefModifier <<= 2u; | ||||
} | ||||
/* Initializations of last stage */ | ||||
n1 = n2; | ||||
n2 >>= 2u; | ||||
/* Calculations of last stage */ | ||||
for (i0 = 0u; i0 <= (fftLen - n1); i0 += n1) | ||||
{ | ||||
/* index calculation for the input as, */ | ||||
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */ | ||||
i1 = i0 + n2; | ||||
i2 = i1 + n2; | ||||
i3 = i2 + n2; | ||||
/* Butterfly implementation */ | ||||
/* xa + xc */ | ||||
r1 = pSrc[2u * i0] + pSrc[2u * i2]; | ||||
/* xa - xc */ | ||||
r2 = pSrc[2u * i0] - pSrc[2u * i2]; | ||||
/* ya + yc */ | ||||
s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u]; | ||||
/* ya - yc */ | ||||
s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u]; | ||||
/* xc + xd */ | ||||
t1 = pSrc[2u * i1] + pSrc[2u * i3]; | ||||
/* xa' = xa + xb + xc + xd */ | ||||
pSrc[2u * i0] = (r1 + t1) * onebyfftLen; | ||||
/* (xa + xb) - (xc + xd) */ | ||||
r1 = r1 - t1; | ||||
/* yb + yd */ | ||||
t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u]; | ||||
/* ya' = ya + yb + yc + yd */ | ||||
pSrc[(2u * i0) + 1u] = (s1 + t2) * onebyfftLen; | ||||
/* (ya + yc) - (yb + yd) */ | ||||
s1 = s1 - t2; | ||||
/* (yb-yd) */ | ||||
t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u]; | ||||
/* (xb-xd) */ | ||||
t2 = pSrc[2u * i1] - pSrc[2u * i3]; | ||||
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */ | ||||
pSrc[2u * i1] = r1 * onebyfftLen; | ||||
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */ | ||||
pSrc[(2u * i1) + 1u] = s1 * onebyfftLen; | ||||
/* (xa - xc) - (yb-yd) */ | ||||
r1 = r2 - t1; | ||||
/* (xa - xc) + (yb-yd) */ | ||||
r2 = r2 + t1; | ||||
/* (ya - yc) + (xb-xd) */ | ||||
s1 = s2 + t2; | ||||
/* (ya - yc) - (xb-xd) */ | ||||
s2 = s2 - t2; | ||||
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */ | ||||
pSrc[2u * i2] = r1 * onebyfftLen; | ||||
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */ | ||||
pSrc[(2u * i2) + 1u] = s1 * onebyfftLen; | ||||
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */ | ||||
pSrc[2u * i3] = r2 * onebyfftLen; | ||||
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */ | ||||
pSrc[(2u * i3) + 1u] = s2 * onebyfftLen; | ||||
} | ||||
#endif /* #ifndef ARM_MATH_CM0 */ | ||||
} | ||||
/* | ||||
* @brief In-place bit reversal function. | ||||
* @param[in, out] *pSrc points to the in-place buffer of floating-point data type. | ||||
* @param[in] fftSize length of the FFT. | ||||
* @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table. | ||||
* @param[in] *pBitRevTab points to the bit reversal table. | ||||
* @return none. | ||||
*/ | ||||
void arm_bitreversal_f32( | ||||
float32_t * pSrc, | ||||
uint16_t fftSize, | ||||
uint16_t bitRevFactor, | ||||
uint16_t * pBitRevTab) | ||||
{ | ||||
uint16_t fftLenBy2, fftLenBy2p1; | ||||
uint16_t i, j; | ||||
float32_t in; | ||||
/* Initializations */ | ||||
j = 0u; | ||||
fftLenBy2 = fftSize >> 1u; | ||||
fftLenBy2p1 = (fftSize >> 1u) + 1u; | ||||
/* Bit Reversal Implementation */ | ||||
for (i = 0u; i <= (fftLenBy2 - 2u); i += 2u) | ||||
{ | ||||
if(i < j) | ||||
{ | ||||
/* pSrc[i] <-> pSrc[j]; */ | ||||
in = pSrc[2u * i]; | ||||
pSrc[2u * i] = pSrc[2u * j]; | ||||
pSrc[2u * j] = in; | ||||
/* pSrc[i+1u] <-> pSrc[j+1u] */ | ||||
in = pSrc[(2u * i) + 1u]; | ||||
pSrc[(2u * i) + 1u] = pSrc[(2u * j) + 1u]; | ||||
pSrc[(2u * j) + 1u] = in; | ||||
/* pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */ | ||||
in = pSrc[2u * (i + fftLenBy2p1)]; | ||||
pSrc[2u * (i + fftLenBy2p1)] = pSrc[2u * (j + fftLenBy2p1)]; | ||||
pSrc[2u * (j + fftLenBy2p1)] = in; | ||||
/* pSrc[i+fftLenBy2p1+1u] <-> pSrc[j+fftLenBy2p1+1u] */ | ||||
in = pSrc[(2u * (i + fftLenBy2p1)) + 1u]; | ||||
pSrc[(2u * (i + fftLenBy2p1)) + 1u] = | ||||
pSrc[(2u * (j + fftLenBy2p1)) + 1u]; | ||||
pSrc[(2u * (j + fftLenBy2p1)) + 1u] = in; | ||||
} | ||||
/* pSrc[i+1u] <-> pSrc[j+1u] */ | ||||
in = pSrc[2u * (i + 1u)]; | ||||
pSrc[2u * (i + 1u)] = pSrc[2u * (j + fftLenBy2)]; | ||||
pSrc[2u * (j + fftLenBy2)] = in; | ||||
/* pSrc[i+2u] <-> pSrc[j+2u] */ | ||||
in = pSrc[(2u * (i + 1u)) + 1u]; | ||||
pSrc[(2u * (i + 1u)) + 1u] = pSrc[(2u * (j + fftLenBy2)) + 1u]; | ||||
pSrc[(2u * (j + fftLenBy2)) + 1u] = in; | ||||
/* Reading the index for the bit reversal */ | ||||
j = *pBitRevTab; | ||||
/* Updating the bit reversal index depending on the fft length */ | ||||
pBitRevTab += bitRevFactor; | ||||
} | ||||
} | ||||