/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_rfft_q15.c
* Description: RFFT & RIFFT Q15 process function
*
* $Date: 27. January 2017
* $Revision: V.1.5.1
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2017 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"
/* ----------------------------------------------------------------------
* Internal functions prototypes
* -------------------------------------------------------------------- */
void arm_split_rfft_q15(
q15_t * pSrc,
uint32_t fftLen,
q15_t * pATable,
q15_t * pBTable,
q15_t * pDst,
uint32_t modifier);
void arm_split_rifft_q15(
q15_t * pSrc,
uint32_t fftLen,
q15_t * pATable,
q15_t * pBTable,
q15_t * pDst,
uint32_t modifier);
/**
* @addtogroup RealFFT
* @{
*/
/**
* @brief Processing function for the Q15 RFFT/RIFFT.
* @param[in] *S points to an instance of the Q15 RFFT/RIFFT structure.
* @param[in] *pSrc points to the input buffer.
* @param[out] *pDst points to the output buffer.
* @return none.
*
* \par Input an output formats:
* \par
* Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process.
* Hence the output format is different for different RFFT sizes.
* The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:
* \par
* \image html RFFTQ15.gif "Input and Output Formats for Q15 RFFT"
* \par
* \image html RIFFTQ15.gif "Input and Output Formats for Q15 RIFFT"
*/
void arm_rfft_q15(
const arm_rfft_instance_q15 * S,
q15_t * pSrc,
q15_t * pDst)
{
const arm_cfft_instance_q15 *S_CFFT = S->pCfft;
uint32_t i;
uint32_t L2 = S->fftLenReal >> 1;
/* Calculation of RIFFT of input */
if (S->ifftFlagR == 1U)
{
/* Real IFFT core process */
arm_split_rifft_q15(pSrc, L2, S->pTwiddleAReal,
S->pTwiddleBReal, pDst, S->twidCoefRModifier);
/* Complex IFFT process */
arm_cfft_q15(S_CFFT, pDst, S->ifftFlagR, S->bitReverseFlagR);
for(i=0;i<S->fftLenReal;i++)
{
pDst[i] = pDst[i] << 1;
}
}
else
{
/* Calculation of RFFT of input */
/* Complex FFT process */
arm_cfft_q15(S_CFFT, pSrc, S->ifftFlagR, S->bitReverseFlagR);
/* Real FFT core process */
arm_split_rfft_q15(pSrc, L2, S->pTwiddleAReal,
S->pTwiddleBReal, pDst, S->twidCoefRModifier);
}
}
/**
* @} end of RealFFT group
*/
/**
* @brief Core Real FFT process
* @param *pSrc points to the input buffer.
* @param fftLen length of FFT.
* @param *pATable points to the A twiddle Coef buffer.
* @param *pBTable points to the B twiddle Coef buffer.
* @param *pDst points to the output buffer.
* @param modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
* @return none.
* The function implements a Real FFT
*/
void arm_split_rfft_q15(
q15_t * pSrc,
uint32_t fftLen,
q15_t * pATable,
q15_t * pBTable,
q15_t * pDst,
uint32_t modifier)
{
uint32_t i; /* Loop Counter */
q31_t outR, outI; /* Temporary variables for output */
q15_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
q15_t *pSrc1, *pSrc2;
#if defined (ARM_MATH_DSP)
q15_t *pD1, *pD2;
#endif
// pSrc[2U * fftLen] = pSrc[0];
// pSrc[(2U * fftLen) + 1U] = pSrc[1];
pCoefA = &pATable[modifier * 2U];
pCoefB = &pBTable[modifier * 2U];
pSrc1 = &pSrc[2];
pSrc2 = &pSrc[(2U * fftLen) - 2U];
#if defined (ARM_MATH_DSP)
/* Run the below code for Cortex-M4 and Cortex-M3 */
i = 1U;
pD1 = pDst + 2;
pD2 = pDst + (4U * fftLen) - 2;
for(i = fftLen - 1; i > 0; i--)
{
/*
outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]
+ pSrc[2 * n - 2 * i] * pBTable[2 * i] +
pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
*/
/* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +
pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */
#ifndef ARM_MATH_BIG_ENDIAN
/* pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1] */
outR = __SMUSD(*__SIMD32(pSrc1), *__SIMD32(pCoefA));
#else
/* -(pSrc[2 * i + 1] * pATable[2 * i + 1] - pSrc[2 * i] * pATable[2 * i]) */
outR = -(__SMUSD(*__SIMD32(pSrc1), *__SIMD32(pCoefA)));
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* pSrc[2 * n - 2 * i] * pBTable[2 * i] +
pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]) */
outR = __SMLAD(*__SIMD32(pSrc2), *__SIMD32(pCoefB), outR) >> 16U;
/* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
#ifndef ARM_MATH_BIG_ENDIAN
outI = __SMUSDX(*__SIMD32(pSrc2)--, *__SIMD32(pCoefB));
#else
outI = __SMUSDX(*__SIMD32(pCoefB), *__SIMD32(pSrc2)--);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] */
outI = __SMLADX(*__SIMD32(pSrc1)++, *__SIMD32(pCoefA), outI);
/* write output */
*pD1++ = (q15_t) outR;
*pD1++ = outI >> 16U;
/* write complex conjugate output */
pD2[0] = (q15_t) outR;
pD2[1] = -(outI >> 16U);
pD2 -= 2;
/* update coefficient pointer */
pCoefB = pCoefB + (2U * modifier);
pCoefA = pCoefA + (2U * modifier);
}
pDst[2U * fftLen] = (pSrc[0] - pSrc[1]) >> 1;
pDst[(2U * fftLen) + 1U] = 0;
pDst[0] = (pSrc[0] + pSrc[1]) >> 1;
pDst[1] = 0;
#else
/* Run the below code for Cortex-M0 */
i = 1U;
while (i < fftLen)
{
/*
outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]
+ pSrc[2 * n - 2 * i] * pBTable[2 * i] +
pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
*/
outR = *pSrc1 * *pCoefA;
outR = outR - (*(pSrc1 + 1) * *(pCoefA + 1));
outR = outR + (*pSrc2 * *pCoefB);
outR = (outR + (*(pSrc2 + 1) * *(pCoefB + 1))) >> 16;
/* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +
pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
*/
outI = *pSrc2 * *(pCoefB + 1);
outI = outI - (*(pSrc2 + 1) * *pCoefB);
outI = outI + (*(pSrc1 + 1) * *pCoefA);
outI = outI + (*pSrc1 * *(pCoefA + 1));
/* update input pointers */
pSrc1 += 2U;
pSrc2 -= 2U;
/* write output */
pDst[2U * i] = (q15_t) outR;
pDst[(2U * i) + 1U] = outI >> 16U;
/* write complex conjugate output */
pDst[(4U * fftLen) - (2U * i)] = (q15_t) outR;
pDst[((4U * fftLen) - (2U * i)) + 1U] = -(outI >> 16U);
/* update coefficient pointer */
pCoefB = pCoefB + (2U * modifier);
pCoefA = pCoefA + (2U * modifier);
i++;
}
pDst[2U * fftLen] = (pSrc[0] - pSrc[1]) >> 1;
pDst[(2U * fftLen) + 1U] = 0;
pDst[0] = (pSrc[0] + pSrc[1]) >> 1;
pDst[1] = 0;
#endif /* #if defined (ARM_MATH_DSP) */
}
/**
* @brief Core Real IFFT process
* @param[in] *pSrc points to the input buffer.
* @param[in] fftLen length of FFT.
* @param[in] *pATable points to the twiddle Coef A buffer.
* @param[in] *pBTable points to the twiddle Coef B buffer.
* @param[out] *pDst points to the output buffer.
* @param[in] modifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
* @return none.
* The function implements a Real IFFT
*/
void arm_split_rifft_q15(
q15_t * pSrc,
uint32_t fftLen,
q15_t * pATable,
q15_t * pBTable,
q15_t * pDst,
uint32_t modifier)
{
uint32_t i; /* Loop Counter */
q31_t outR, outI; /* Temporary variables for output */
q15_t *pCoefA, *pCoefB; /* Temporary pointers for twiddle factors */
q15_t *pSrc1, *pSrc2;
q15_t *pDst1 = &pDst[0];
pCoefA = &pATable[0];
pCoefB = &pBTable[0];
pSrc1 = &pSrc[0];
pSrc2 = &pSrc[2U * fftLen];
#if defined (ARM_MATH_DSP)
/* Run the below code for Cortex-M4 and Cortex-M3 */
i = fftLen;
while (i > 0U)
{
/*
outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
pIn[2 * n - 2 * i] * pBTable[2 * i] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -
pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
*/
#ifndef ARM_MATH_BIG_ENDIAN
/* pIn[2 * n - 2 * i] * pBTable[2 * i] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]) */
outR = __SMUSD(*__SIMD32(pSrc2), *__SIMD32(pCoefB));
#else
/* -(-pIn[2 * n - 2 * i] * pBTable[2 * i] +
pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1])) */
outR = -(__SMUSD(*__SIMD32(pSrc2), *__SIMD32(pCoefB)));
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
pIn[2 * n - 2 * i] * pBTable[2 * i] */
outR = __SMLAD(*__SIMD32(pSrc1), *__SIMD32(pCoefA), outR) >> 16U;
/*
-pIn[2 * n - 2 * i] * pBTable[2 * i + 1] +
pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
outI = __SMUADX(*__SIMD32(pSrc2)--, *__SIMD32(pCoefB));
/* pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] */
#ifndef ARM_MATH_BIG_ENDIAN
outI = __SMLSDX(*__SIMD32(pCoefA), *__SIMD32(pSrc1)++, -outI);
#else
outI = __SMLSDX(*__SIMD32(pSrc1)++, *__SIMD32(pCoefA), -outI);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* write output */
#ifndef ARM_MATH_BIG_ENDIAN
*__SIMD32(pDst1)++ = __PKHBT(outR, (outI >> 16U), 16);
#else
*__SIMD32(pDst1)++ = __PKHBT((outI >> 16U), outR, 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* update coefficient pointer */
pCoefB = pCoefB + (2U * modifier);
pCoefA = pCoefA + (2U * modifier);
i--;
}
#else
/* Run the below code for Cortex-M0 */
i = fftLen;
while (i > 0U)
{
/*
outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
pIn[2 * n - 2 * i] * pBTable[2 * i] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
*/
outR = *pSrc2 * *pCoefB;
outR = outR - (*(pSrc2 + 1) * *(pCoefB + 1));
outR = outR + (*pSrc1 * *pCoefA);
outR = (outR + (*(pSrc1 + 1) * *(pCoefA + 1))) >> 16;
/*
outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -
pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
*/
outI = *(pSrc1 + 1) * *pCoefA;
outI = outI - (*pSrc1 * *(pCoefA + 1));
outI = outI - (*pSrc2 * *(pCoefB + 1));
outI = outI - (*(pSrc2 + 1) * *(pCoefB));
/* update input pointers */
pSrc1 += 2U;
pSrc2 -= 2U;
/* write output */
*pDst1++ = (q15_t) outR;
*pDst1++ = (q15_t) (outI >> 16);
/* update coefficient pointer */
pCoefB = pCoefB + (2U * modifier);
pCoefA = pCoefA + (2U * modifier);
i--;
}
#endif /* #if defined (ARM_MATH_DSP) */
}