DSP/Source/TransformFunctions/arm_cfft_radix2_f32.c - third_party/github/STMicroelectronics/cmsis_core - Git at Google

 /* ----------------------------------------------------------------------
  * Project:      CMSIS DSP Library
  * Title:        arm_cfft_radix2_f32.c
  * Description:  Radix-2 Decimation in Frequency CFFT & CIFFT Floating point processing function
  *
  * $Date:        18. March 2019
  * $Revision:    V1.6.0
  *
  * Target Processor: Cortex-M cores
  * -------------------------------------------------------------------- */
 /*
  * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
  *
  * SPDX-License-Identifier: Apache-2.0
  *
  * Licensed under the Apache License, Version 2.0 (the License); you may
  * not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  * www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "arm_math.h"

 void arm_radix2_butterfly_f32(
         float32_t * pSrc,
         uint32_t fftLen,
   const float32_t * pCoef,
         uint16_t twidCoefModifier);

 void arm_radix2_butterfly_inverse_f32(
         float32_t * pSrc,
         uint32_t fftLen,
   const float32_t * pCoef,
         uint16_t twidCoefModifier,
         float32_t onebyfftLen);

 extern void arm_bitreversal_f32(
         float32_t * pSrc,
         uint16_t fftSize,
         uint16_t bitRevFactor,
   const uint16_t * pBitRevTab);

 /**
   @ingroup groupTransforms
  */

 /**
   @addtogroup ComplexFFT
   @{
  */

 /**
   @brief         Radix-2 CFFT/CIFFT.
   @deprecated    Do not use this function. It has been superseded by \ref arm_cfft_f32 and will be removed in the future
   @param[in]     S    points to an instance of the floating-point Radix-2 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_radix2_f32(
 const arm_cfft_radix2_instance_f32 * S,
       float32_t * pSrc)
 {

    if (S->ifftFlag == 1U)
    {
       /* Complex IFFT radix-2 */
       arm_radix2_butterfly_inverse_f32(pSrc, S->fftLen, S->pTwiddle,
       S->twidCoefModifier, S->onebyfftLen);
    }
    else
    {
       /* Complex FFT radix-2 */
       arm_radix2_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 ComplexFFT group
  */


 /* ----------------------------------------------------------------------
  ** Internal helper function used by the FFTs
  ** ------------------------------------------------------------------- */

 /**
   brief  Core function for the floating-point CFFT butterfly process.
   param[in,out] pSrc             points to 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
   return        none
  */

 void arm_radix2_butterfly_f32(
         float32_t * pSrc,
         uint32_t fftLen,
   const float32_t * pCoef,
         uint16_t twidCoefModifier)
 {

         uint32_t i, j, k, l;
         uint32_t n1, n2, ia;
         float32_t xt, yt, cosVal, sinVal;
         float32_t p0, p1, p2, p3;
         float32_t a0, a1;

 #if defined (ARM_MATH_DSP)

    /*  Initializations for the first stage */
    n2 = fftLen >> 1;
    ia = 0;
    i = 0;

    // loop for groups
    for (k = n2; k > 0; k--)
    {
       cosVal = pCoef[ia * 2];
       sinVal = pCoef[(ia * 2) + 1];

       /*  Twiddle coefficients index modifier */
       ia += twidCoefModifier;

       /*  index calculation for the input as, */
       /*  pSrc[i + 0], pSrc[i + fftLen/1] */
       l = i + n2;

       /*  Butterfly implementation */
       a0 = pSrc[2 * i] + pSrc[2 * l];
       xt = pSrc[2 * i] - pSrc[2 * l];

       yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
       a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

       p0 = xt * cosVal;
       p1 = yt * sinVal;
       p2 = yt * cosVal;
       p3 = xt * sinVal;

       pSrc[2 * i]     = a0;
       pSrc[2 * i + 1] = a1;

       pSrc[2 * l]     = p0 + p1;
       pSrc[2 * l + 1] = p2 - p3;

       i++;
    }                             // groups loop end

    twidCoefModifier <<= 1U;

    // loop for stage
    for (k = n2; k > 2; k = k >> 1)
    {
       n1 = n2;
       n2 = n2 >> 1;
       ia = 0;

       // loop for groups
       j = 0;
       do
       {
          cosVal = pCoef[ia * 2];
          sinVal = pCoef[(ia * 2) + 1];
          ia += twidCoefModifier;

          // loop for butterfly
          i = j;
          do
          {
             l = i + n2;
             a0 = pSrc[2 * i] + pSrc[2 * l];
             xt = pSrc[2 * i] - pSrc[2 * l];

             yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
             a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

             p0 = xt * cosVal;
             p1 = yt * sinVal;
             p2 = yt * cosVal;
             p3 = xt * sinVal;

             pSrc[2 * i] = a0;
             pSrc[2 * i + 1] = a1;

             pSrc[2 * l]     = p0 + p1;
             pSrc[2 * l + 1] = p2 - p3;

             i += n1;
          } while ( i < fftLen );                        // butterfly loop end
          j++;
       } while ( j < n2);                          // groups loop end
       twidCoefModifier <<= 1U;
    }                             // stages loop end

    // loop for butterfly
    for (i = 0; i < fftLen; i += 2)
    {
       a0 = pSrc[2 * i] + pSrc[2 * i + 2];
       xt = pSrc[2 * i] - pSrc[2 * i + 2];

       yt = pSrc[2 * i + 1] - pSrc[2 * i + 3];
       a1 = pSrc[2 * i + 3] + pSrc[2 * i + 1];

       pSrc[2 * i] = a0;
       pSrc[2 * i + 1] = a1;
       pSrc[2 * i + 2] = xt;
       pSrc[2 * i + 3] = yt;
    }                             // groups loop end

 #else /* #if defined (ARM_MATH_DSP) */

    n2 = fftLen;

    // loop for stage
    for (k = fftLen; k > 1; k = k >> 1)
    {
       n1 = n2;
       n2 = n2 >> 1;
       ia = 0;

       // loop for groups
       j = 0;
       do
       {
          cosVal = pCoef[ia * 2];
          sinVal = pCoef[(ia * 2) + 1];
          ia += twidCoefModifier;

          // loop for butterfly
          i = j;
          do
          {
             l = i + n2;
             a0 = pSrc[2 * i] + pSrc[2 * l];
             xt = pSrc[2 * i] - pSrc[2 * l];

             yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
             a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

             p0 = xt * cosVal;
             p1 = yt * sinVal;
             p2 = yt * cosVal;
             p3 = xt * sinVal;

             pSrc[2 * i] = a0;
             pSrc[2 * i + 1] = a1;

             pSrc[2 * l]     = p0 + p1;
             pSrc[2 * l + 1] = p2 - p3;

             i += n1;
          } while (i < fftLen);
          j++;
       } while (j < n2);
       twidCoefModifier <<= 1U;
    }

 #endif /* #if defined (ARM_MATH_DSP) */

 }


 void arm_radix2_butterfly_inverse_f32(
         float32_t * pSrc,
         uint32_t fftLen,
   const float32_t * pCoef,
         uint16_t twidCoefModifier,
         float32_t onebyfftLen)
 {

         uint32_t i, j, k, l;
         uint32_t n1, n2, ia;
         float32_t xt, yt, cosVal, sinVal;
         float32_t p0, p1, p2, p3;
         float32_t a0, a1;

 #if defined (ARM_MATH_DSP)

    n2 = fftLen >> 1;
    ia = 0;

    // loop for groups
    for (i = 0; i < n2; i++)
    {
       cosVal = pCoef[ia * 2];
       sinVal = pCoef[(ia * 2) + 1];
       ia += twidCoefModifier;

       l = i + n2;
       a0 = pSrc[2 * i] + pSrc[2 * l];
       xt = pSrc[2 * i] - pSrc[2 * l];

       yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
       a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

       p0 = xt * cosVal;
       p1 = yt * sinVal;
       p2 = yt * cosVal;
       p3 = xt * sinVal;

       pSrc[2 * i] = a0;
       pSrc[2 * i + 1] = a1;

       pSrc[2 * l]     = p0 - p1;
       pSrc[2 * l + 1] = p2 + p3;
    }                             // groups loop end

    twidCoefModifier <<= 1U;

    // loop for stage
    for (k = fftLen / 2; k > 2; k = k >> 1)
    {
       n1 = n2;
       n2 = n2 >> 1;
       ia = 0;

       // loop for groups
       j = 0;
       do
       {
          cosVal = pCoef[ia * 2];
          sinVal = pCoef[(ia * 2) + 1];
          ia += twidCoefModifier;

          // loop for butterfly
          i = j;
          do
          {
             l = i + n2;
             a0 = pSrc[2 * i] + pSrc[2 * l];
             xt = pSrc[2 * i] - pSrc[2 * l];

             yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
             a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

             p0 = xt * cosVal;
             p1 = yt * sinVal;
             p2 = yt * cosVal;
             p3 = xt * sinVal;

             pSrc[2 * i] = a0;
             pSrc[2 * i + 1] = a1;

             pSrc[2 * l]     = p0 - p1;
             pSrc[2 * l + 1] = p2 + p3;

             i += n1;
          } while ( i < fftLen );                 // butterfly loop end
          j++;
       } while (j < n2);                      // groups loop end

       twidCoefModifier <<= 1U;
    }                             // stages loop end

    // loop for butterfly
    for (i = 0; i < fftLen; i += 2)
    {
       a0 = pSrc[2 * i] + pSrc[2 * i + 2];
       xt = pSrc[2 * i] - pSrc[2 * i + 2];

       a1 = pSrc[2 * i + 3] + pSrc[2 * i + 1];
       yt = pSrc[2 * i + 1] - pSrc[2 * i + 3];

       p0 = a0 * onebyfftLen;
       p2 = xt * onebyfftLen;
       p1 = a1 * onebyfftLen;
       p3 = yt * onebyfftLen;

       pSrc[2 * i] = p0;
       pSrc[2 * i + 1] = p1;
       pSrc[2 * i + 2] = p2;
       pSrc[2 * i + 3] = p3;
    }                             // butterfly loop end

 #else /* #if defined (ARM_MATH_DSP) */

    n2 = fftLen;

    // loop for stage
    for (k = fftLen; k > 2; k = k >> 1)
    {
       n1 = n2;
       n2 = n2 >> 1;
       ia = 0;

       // loop for groups
       j = 0;
       do
       {
          cosVal = pCoef[ia * 2];
          sinVal = pCoef[(ia * 2) + 1];
          ia = ia + twidCoefModifier;

          // loop for butterfly
          i = j;
          do
          {
             l = i + n2;
             a0 = pSrc[2 * i] + pSrc[2 * l];
             xt = pSrc[2 * i] - pSrc[2 * l];

             yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
             a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

             p0 = xt * cosVal;
             p1 = yt * sinVal;
             p2 = yt * cosVal;
             p3 = xt * sinVal;

             pSrc[2 * i] = a0;
             pSrc[2 * i + 1] = a1;

             pSrc[2 * l]     = p0 - p1;
             pSrc[2 * l + 1] = p2 + p3;

             i += n1;
          } while ( i < fftLen );                    // butterfly loop end
          j++;
       } while ( j < n2 );                      // groups loop end

       twidCoefModifier = twidCoefModifier << 1U;
    }                             // stages loop end

    n1 = n2;
    n2 = n2 >> 1;

    // loop for butterfly
    for (i = 0; i < fftLen; i += n1)
    {
       l = i + n2;

       a0 = pSrc[2 * i] + pSrc[2 * l];
       xt = pSrc[2 * i] - pSrc[2 * l];

       a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];
       yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];

       p0 = a0 * onebyfftLen;
       p2 = xt * onebyfftLen;
       p1 = a1 * onebyfftLen;
       p3 = yt * onebyfftLen;

       pSrc[2 * i] = p0;
       pSrc[2 * l] = p2;

       pSrc[2 * i + 1] = p1;
       pSrc[2 * l + 1] = p3;
    }                             // butterfly loop end

 #endif /* #if defined (ARM_MATH_DSP) */

 }
	/* ----------------------------------------------------------------------
	* Project: CMSIS DSP Library
	* Title: arm_cfft_radix2_f32.c
	* Description: Radix-2 Decimation in Frequency CFFT & CIFFT Floating point processing function
	*
	* $Date: 18. March 2019
	* $Revision: V1.6.0
	*
	* Target Processor: Cortex-M cores
	* -------------------------------------------------------------------- */
	/*
	* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
	*
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the License); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an AS IS BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "arm_math.h"

	void arm_radix2_butterfly_f32(
	float32_t * pSrc,
	uint32_t fftLen,
	const float32_t * pCoef,
	uint16_t twidCoefModifier);

	void arm_radix2_butterfly_inverse_f32(
	float32_t * pSrc,
	uint32_t fftLen,
	const float32_t * pCoef,
	uint16_t twidCoefModifier,
	float32_t onebyfftLen);

	extern void arm_bitreversal_f32(
	float32_t * pSrc,
	uint16_t fftSize,
	uint16_t bitRevFactor,
	const uint16_t * pBitRevTab);

	/**
	@ingroup groupTransforms
	*/

	/**
	@addtogroup ComplexFFT
	@{
	*/

	/**
	@brief Radix-2 CFFT/CIFFT.
	@deprecated Do not use this function. It has been superseded by \ref arm_cfft_f32 and will be removed in the future
	@param[in] S points to an instance of the floating-point Radix-2 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_radix2_f32(
	const arm_cfft_radix2_instance_f32 * S,
	float32_t * pSrc)
	{

	if (S->ifftFlag == 1U)
	{
	/* Complex IFFT radix-2 */
	arm_radix2_butterfly_inverse_f32(pSrc, S->fftLen, S->pTwiddle,
	S->twidCoefModifier, S->onebyfftLen);
	}
	else
	{
	/* Complex FFT radix-2 */
	arm_radix2_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 ComplexFFT group
	*/



	/* ----------------------------------------------------------------------
	** Internal helper function used by the FFTs
	** ------------------------------------------------------------------- */

	/**
	brief Core function for the floating-point CFFT butterfly process.
	param[in,out] pSrc points to 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
	return none
	*/

	void arm_radix2_butterfly_f32(
	float32_t * pSrc,
	uint32_t fftLen,
	const float32_t * pCoef,
	uint16_t twidCoefModifier)
	{

	uint32_t i, j, k, l;
	uint32_t n1, n2, ia;
	float32_t xt, yt, cosVal, sinVal;
	float32_t p0, p1, p2, p3;
	float32_t a0, a1;

	#if defined (ARM_MATH_DSP)

	/* Initializations for the first stage */
	n2 = fftLen >> 1;
	ia = 0;
	i = 0;

	// loop for groups
	for (k = n2; k > 0; k--)
	{
	cosVal = pCoef[ia * 2];
	sinVal = pCoef[(ia * 2) + 1];

	/* Twiddle coefficients index modifier */
	ia += twidCoefModifier;

	/* index calculation for the input as, */
	/* pSrc[i + 0], pSrc[i + fftLen/1] */
	l = i + n2;

	/* Butterfly implementation */
	a0 = pSrc[2 * i] + pSrc[2 * l];
	xt = pSrc[2 * i] - pSrc[2 * l];

	yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
	a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

	p0 = xt * cosVal;
	p1 = yt * sinVal;
	p2 = yt * cosVal;
	p3 = xt * sinVal;

	pSrc[2 * i] = a0;
	pSrc[2 * i + 1] = a1;

	pSrc[2 * l] = p0 + p1;
	pSrc[2 * l + 1] = p2 - p3;

	i++;
	} // groups loop end

	twidCoefModifier <<= 1U;

	// loop for stage
	for (k = n2; k > 2; k = k >> 1)
	{
	n1 = n2;
	n2 = n2 >> 1;
	ia = 0;

	// loop for groups
	j = 0;
	do
	{
	cosVal = pCoef[ia * 2];
	sinVal = pCoef[(ia * 2) + 1];
	ia += twidCoefModifier;

	// loop for butterfly
	i = j;
	do
	{
	l = i + n2;
	a0 = pSrc[2 * i] + pSrc[2 * l];
	xt = pSrc[2 * i] - pSrc[2 * l];

	yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
	a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

	p0 = xt * cosVal;
	p1 = yt * sinVal;
	p2 = yt * cosVal;
	p3 = xt * sinVal;

	pSrc[2 * i] = a0;
	pSrc[2 * i + 1] = a1;

	pSrc[2 * l] = p0 + p1;
	pSrc[2 * l + 1] = p2 - p3;

	i += n1;
	} while ( i < fftLen ); // butterfly loop end
	j++;
	} while ( j < n2); // groups loop end
	twidCoefModifier <<= 1U;
	} // stages loop end

	// loop for butterfly
	for (i = 0; i < fftLen; i += 2)
	{
	a0 = pSrc[2 * i] + pSrc[2 * i + 2];
	xt = pSrc[2 * i] - pSrc[2 * i + 2];

	yt = pSrc[2 * i + 1] - pSrc[2 * i + 3];
	a1 = pSrc[2 * i + 3] + pSrc[2 * i + 1];

	pSrc[2 * i] = a0;
	pSrc[2 * i + 1] = a1;
	pSrc[2 * i + 2] = xt;
	pSrc[2 * i + 3] = yt;
	} // groups loop end

	#else /* #if defined (ARM_MATH_DSP) */

	n2 = fftLen;

	// loop for stage
	for (k = fftLen; k > 1; k = k >> 1)
	{
	n1 = n2;
	n2 = n2 >> 1;
	ia = 0;

	// loop for groups
	j = 0;
	do
	{
	cosVal = pCoef[ia * 2];
	sinVal = pCoef[(ia * 2) + 1];
	ia += twidCoefModifier;

	// loop for butterfly
	i = j;
	do
	{
	l = i + n2;
	a0 = pSrc[2 * i] + pSrc[2 * l];
	xt = pSrc[2 * i] - pSrc[2 * l];

	yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
	a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

	p0 = xt * cosVal;
	p1 = yt * sinVal;
	p2 = yt * cosVal;
	p3 = xt * sinVal;

	pSrc[2 * i] = a0;
	pSrc[2 * i + 1] = a1;

	pSrc[2 * l] = p0 + p1;
	pSrc[2 * l + 1] = p2 - p3;

	i += n1;
	} while (i < fftLen);
	j++;
	} while (j < n2);
	twidCoefModifier <<= 1U;
	}

	#endif /* #if defined (ARM_MATH_DSP) */

	}


	void arm_radix2_butterfly_inverse_f32(
	float32_t * pSrc,
	uint32_t fftLen,
	const float32_t * pCoef,
	uint16_t twidCoefModifier,
	float32_t onebyfftLen)
	{

	uint32_t i, j, k, l;
	uint32_t n1, n2, ia;
	float32_t xt, yt, cosVal, sinVal;
	float32_t p0, p1, p2, p3;
	float32_t a0, a1;

	#if defined (ARM_MATH_DSP)

	n2 = fftLen >> 1;
	ia = 0;

	// loop for groups
	for (i = 0; i < n2; i++)
	{
	cosVal = pCoef[ia * 2];
	sinVal = pCoef[(ia * 2) + 1];
	ia += twidCoefModifier;

	l = i + n2;
	a0 = pSrc[2 * i] + pSrc[2 * l];
	xt = pSrc[2 * i] - pSrc[2 * l];

	yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
	a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

	p0 = xt * cosVal;
	p1 = yt * sinVal;
	p2 = yt * cosVal;
	p3 = xt * sinVal;

	pSrc[2 * i] = a0;
	pSrc[2 * i + 1] = a1;

	pSrc[2 * l] = p0 - p1;
	pSrc[2 * l + 1] = p2 + p3;
	} // groups loop end

	twidCoefModifier <<= 1U;

	// loop for stage
	for (k = fftLen / 2; k > 2; k = k >> 1)
	{
	n1 = n2;
	n2 = n2 >> 1;
	ia = 0;

	// loop for groups
	j = 0;
	do
	{
	cosVal = pCoef[ia * 2];
	sinVal = pCoef[(ia * 2) + 1];
	ia += twidCoefModifier;

	// loop for butterfly
	i = j;
	do
	{
	l = i + n2;
	a0 = pSrc[2 * i] + pSrc[2 * l];
	xt = pSrc[2 * i] - pSrc[2 * l];

	yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
	a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

	p0 = xt * cosVal;
	p1 = yt * sinVal;
	p2 = yt * cosVal;
	p3 = xt * sinVal;

	pSrc[2 * i] = a0;
	pSrc[2 * i + 1] = a1;

	pSrc[2 * l] = p0 - p1;
	pSrc[2 * l + 1] = p2 + p3;

	i += n1;
	} while ( i < fftLen ); // butterfly loop end
	j++;
	} while (j < n2); // groups loop end

	twidCoefModifier <<= 1U;
	} // stages loop end

	// loop for butterfly
	for (i = 0; i < fftLen; i += 2)
	{
	a0 = pSrc[2 * i] + pSrc[2 * i + 2];
	xt = pSrc[2 * i] - pSrc[2 * i + 2];

	a1 = pSrc[2 * i + 3] + pSrc[2 * i + 1];
	yt = pSrc[2 * i + 1] - pSrc[2 * i + 3];

	p0 = a0 * onebyfftLen;
	p2 = xt * onebyfftLen;
	p1 = a1 * onebyfftLen;
	p3 = yt * onebyfftLen;

	pSrc[2 * i] = p0;
	pSrc[2 * i + 1] = p1;
	pSrc[2 * i + 2] = p2;
	pSrc[2 * i + 3] = p3;
	} // butterfly loop end

	#else /* #if defined (ARM_MATH_DSP) */

	n2 = fftLen;

	// loop for stage
	for (k = fftLen; k > 2; k = k >> 1)
	{
	n1 = n2;
	n2 = n2 >> 1;
	ia = 0;

	// loop for groups
	j = 0;
	do
	{
	cosVal = pCoef[ia * 2];
	sinVal = pCoef[(ia * 2) + 1];
	ia = ia + twidCoefModifier;

	// loop for butterfly
	i = j;
	do
	{
	l = i + n2;
	a0 = pSrc[2 * i] + pSrc[2 * l];
	xt = pSrc[2 * i] - pSrc[2 * l];

	yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
	a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];

	p0 = xt * cosVal;
	p1 = yt * sinVal;
	p2 = yt * cosVal;
	p3 = xt * sinVal;

	pSrc[2 * i] = a0;
	pSrc[2 * i + 1] = a1;

	pSrc[2 * l] = p0 - p1;
	pSrc[2 * l + 1] = p2 + p3;

	i += n1;
	} while ( i < fftLen ); // butterfly loop end
	j++;
	} while ( j < n2 ); // groups loop end

	twidCoefModifier = twidCoefModifier << 1U;
	} // stages loop end

	n1 = n2;
	n2 = n2 >> 1;

	// loop for butterfly
	for (i = 0; i < fftLen; i += n1)
	{
	l = i + n2;

	a0 = pSrc[2 * i] + pSrc[2 * l];
	xt = pSrc[2 * i] - pSrc[2 * l];

	a1 = pSrc[2 * l + 1] + pSrc[2 * i + 1];
	yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];

	p0 = a0 * onebyfftLen;
	p2 = xt * onebyfftLen;
	p1 = a1 * onebyfftLen;
	p3 = yt * onebyfftLen;

	pSrc[2 * i] = p0;
	pSrc[2 * l] = p2;

	pSrc[2 * i + 1] = p1;
	pSrc[2 * l + 1] = p3;
	} // butterfly loop end

	#endif /* #if defined (ARM_MATH_DSP) */

	}