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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_rfft_f32.c
  4.  * Description:  RFFT & RIFFT Floating point process function
  5.  *
  6.  * $Date:        27. January 2017
  7.  * $Revision:    V.1.5.1
  8.  *
  9.  * Target Processor: Cortex-M cores
  10.  * -------------------------------------------------------------------- */
  11. /*
  12.  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
  13.  *
  14.  * SPDX-License-Identifier: Apache-2.0
  15.  *
  16.  * Licensed under the Apache License, Version 2.0 (the License); you may
  17.  * not use this file except in compliance with the License.
  18.  * You may obtain a copy of the License at
  19.  *
  20.  * www.apache.org/licenses/LICENSE-2.0
  21.  *
  22.  * Unless required by applicable law or agreed to in writing, software
  23.  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  24.  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  25.  * See the License for the specific language governing permissions and
  26.  * limitations under the License.
  27.  */
  28.  
  29. #include "arm_math.h"
  30.  
  31. /* ----------------------------------------------------------------------
  32.  * Internal functions prototypes
  33.  * -------------------------------------------------------------------- */
  34.  
  35. extern void arm_radix4_butterfly_f32(
  36.     float32_t * pSrc,
  37.     uint16_t fftLen,
  38.     float32_t * pCoef,
  39.     uint16_t twidCoefModifier);
  40.  
  41. extern void arm_radix4_butterfly_inverse_f32(
  42.     float32_t * pSrc,
  43.     uint16_t fftLen,
  44.     float32_t * pCoef,
  45.     uint16_t twidCoefModifier,
  46.     float32_t onebyfftLen);
  47.  
  48. extern void arm_bitreversal_f32(
  49.     float32_t * pSrc,
  50.     uint16_t fftSize,
  51.     uint16_t bitRevFactor,
  52.     uint16_t * pBitRevTab);
  53.  
  54. void arm_split_rfft_f32(
  55.   float32_t * pSrc,
  56.   uint32_t fftLen,
  57.   float32_t * pATable,
  58.   float32_t * pBTable,
  59.   float32_t * pDst,
  60.   uint32_t modifier);
  61.  
  62. void arm_split_rifft_f32(
  63.   float32_t * pSrc,
  64.   uint32_t fftLen,
  65.   float32_t * pATable,
  66.   float32_t * pBTable,
  67.   float32_t * pDst,
  68.   uint32_t modifier);
  69.  
  70. /**
  71. * @ingroup groupTransforms
  72. */
  73.  
  74. /**
  75.  * @addtogroup RealFFT
  76.  * @{
  77.  */
  78.  
  79. /**
  80.  * @brief Processing function for the floating-point RFFT/RIFFT.
  81.  * @deprecated Do not use this function.  It has been superceded by \ref arm_rfft_fast_f32 and will be removed
  82.  * in the future.
  83.  * @param[in]  *S    points to an instance of the floating-point RFFT/RIFFT structure.
  84.  * @param[in]  *pSrc points to the input buffer.
  85.  * @param[out] *pDst points to the output buffer.
  86.  * @return none.
  87.  */
  88.  
  89. void arm_rfft_f32(
  90.   const arm_rfft_instance_f32 * S,
  91.   float32_t * pSrc,
  92.   float32_t * pDst)
  93. {
  94.   const arm_cfft_radix4_instance_f32 *S_CFFT = S->pCfft;
  95.  
  96.  
  97.   /* Calculation of Real IFFT of input */
  98.   if (S->ifftFlagR == 1U)
  99.   {
  100.     /*  Real IFFT core process */
  101.     arm_split_rifft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal,
  102.                         S->pTwiddleBReal, pDst, S->twidCoefRModifier);
  103.  
  104.  
  105.     /* Complex radix-4 IFFT process */
  106.     arm_radix4_butterfly_inverse_f32(pDst, S_CFFT->fftLen,
  107.                                      S_CFFT->pTwiddle,
  108.                                      S_CFFT->twidCoefModifier,
  109.                                      S_CFFT->onebyfftLen);
  110.  
  111.     /* Bit reversal process */
  112.     if (S->bitReverseFlagR == 1U)
  113.     {
  114.       arm_bitreversal_f32(pDst, S_CFFT->fftLen,
  115.                           S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
  116.     }
  117.   }
  118.   else
  119.   {
  120.  
  121.     /* Calculation of RFFT of input */
  122.  
  123.     /* Complex radix-4 FFT process */
  124.     arm_radix4_butterfly_f32(pSrc, S_CFFT->fftLen,
  125.                              S_CFFT->pTwiddle, S_CFFT->twidCoefModifier);
  126.  
  127.     /* Bit reversal process */
  128.     if (S->bitReverseFlagR == 1U)
  129.     {
  130.       arm_bitreversal_f32(pSrc, S_CFFT->fftLen,
  131.                           S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
  132.     }
  133.  
  134.  
  135.     /*  Real FFT core process */
  136.     arm_split_rfft_f32(pSrc, S->fftLenBy2, S->pTwiddleAReal,
  137.                        S->pTwiddleBReal, pDst, S->twidCoefRModifier);
  138.   }
  139.  
  140. }
  141.  
  142. /**
  143.    * @} end of RealFFT group
  144.    */
  145.  
  146. /**
  147.  * @brief  Core Real FFT process
  148.  * @param[in]   *pSrc                           points to the input buffer.
  149.  * @param[in]   fftLen                          length of FFT.
  150.  * @param[in]   *pATable                        points to the twiddle Coef A buffer.
  151.  * @param[in]   *pBTable                        points to the twiddle Coef B buffer.
  152.  * @param[out]  *pDst                           points to the output buffer.
  153.  * @param[in]   modifier                twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
  154.  * @return none.
  155.  */
  156.  
  157. void arm_split_rfft_f32(
  158.   float32_t * pSrc,
  159.   uint32_t fftLen,
  160.   float32_t * pATable,
  161.   float32_t * pBTable,
  162.   float32_t * pDst,
  163.   uint32_t modifier)
  164. {
  165.   uint32_t i;                                    /* Loop Counter */
  166.   float32_t outR, outI;                          /* Temporary variables for output */
  167.   float32_t *pCoefA, *pCoefB;                    /* Temporary pointers for twiddle factors */
  168.   float32_t CoefA1, CoefA2, CoefB1;              /* Temporary variables for twiddle coefficients */
  169.   float32_t *pDst1 = &pDst[2], *pDst2 = &pDst[(4U * fftLen) - 1U];      /* temp pointers for output buffer */
  170.   float32_t *pSrc1 = &pSrc[2], *pSrc2 = &pSrc[(2U * fftLen) - 1U];      /* temp pointers for input buffer */
  171.  
  172.   /* Init coefficient pointers */
  173.   pCoefA = &pATable[modifier * 2U];
  174.   pCoefB = &pBTable[modifier * 2U];
  175.  
  176.   i = fftLen - 1U;
  177.  
  178.   while (i > 0U)
  179.   {
  180.     /*
  181.        outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]
  182.        + pSrc[2 * n - 2 * i] * pBTable[2 * i] +
  183.        pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
  184.      */
  185.  
  186.     /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +
  187.        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
  188.        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */
  189.  
  190.     /* read pATable[2 * i] */
  191.     CoefA1 = *pCoefA++;
  192.     /* pATable[2 * i + 1] */
  193.     CoefA2 = *pCoefA;
  194.  
  195.     /* pSrc[2 * i] * pATable[2 * i] */
  196.     outR = *pSrc1 * CoefA1;
  197.     /* pSrc[2 * i] * CoefA2 */
  198.     outI = *pSrc1++ * CoefA2;
  199.  
  200.     /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
  201.     outR -= (*pSrc1 + *pSrc2) * CoefA2;
  202.     /* pSrc[2 * i + 1] * CoefA1 */
  203.     outI += *pSrc1++ * CoefA1;
  204.  
  205.     CoefB1 = *pCoefB;
  206.  
  207.     /* pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
  208.     outI -= *pSrc2-- * CoefB1;
  209.     /* pSrc[2 * fftLen - 2 * i] * CoefA2 */
  210.     outI -= *pSrc2 * CoefA2;
  211.  
  212.     /* pSrc[2 * fftLen - 2 * i] * CoefB1 */
  213.     outR += *pSrc2-- * CoefB1;
  214.  
  215.     /* write output */
  216.     *pDst1++ = outR;
  217.     *pDst1++ = outI;
  218.  
  219.     /* write complex conjugate output */
  220.     *pDst2-- = -outI;
  221.     *pDst2-- = outR;
  222.  
  223.     /* update coefficient pointer */
  224.     pCoefB = pCoefB + (modifier * 2U);
  225.     pCoefA = pCoefA + ((modifier * 2U) - 1U);
  226.  
  227.     i--;
  228.  
  229.   }
  230.  
  231.   pDst[2U * fftLen] = pSrc[0] - pSrc[1];
  232.   pDst[(2U * fftLen) + 1U] = 0.0f;
  233.  
  234.   pDst[0] = pSrc[0] + pSrc[1];
  235.   pDst[1] = 0.0f;
  236.  
  237. }
  238.  
  239.  
  240. /**
  241.  * @brief  Core Real IFFT process
  242.  * @param[in]   *pSrc                           points to the input buffer.
  243.  * @param[in]   fftLen                          length of FFT.
  244.  * @param[in]   *pATable                        points to the twiddle Coef A buffer.
  245.  * @param[in]   *pBTable                        points to the twiddle Coef B buffer.
  246.  * @param[out]  *pDst                           points to the output buffer.
  247.  * @param[in]   modifier                twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
  248.  * @return none.
  249.  */
  250.  
  251. void arm_split_rifft_f32(
  252.   float32_t * pSrc,
  253.   uint32_t fftLen,
  254.   float32_t * pATable,
  255.   float32_t * pBTable,
  256.   float32_t * pDst,
  257.   uint32_t modifier)
  258. {
  259.   float32_t outR, outI;                          /* Temporary variables for output */
  260.   float32_t *pCoefA, *pCoefB;                    /* Temporary pointers for twiddle factors */
  261.   float32_t CoefA1, CoefA2, CoefB1;              /* Temporary variables for twiddle coefficients */
  262.   float32_t *pSrc1 = &pSrc[0], *pSrc2 = &pSrc[(2U * fftLen) + 1U];
  263.  
  264.   pCoefA = &pATable[0];
  265.   pCoefB = &pBTable[0];
  266.  
  267.   while (fftLen > 0U)
  268.   {
  269.     /*
  270.        outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
  271.        pIn[2 * n - 2 * i] * pBTable[2 * i] -
  272.        pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
  273.  
  274.        outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -
  275.        pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
  276.        pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);
  277.  
  278.      */
  279.  
  280.     CoefA1 = *pCoefA++;
  281.     CoefA2 = *pCoefA;
  282.  
  283.     /* outR = (pSrc[2 * i] * CoefA1 */
  284.     outR = *pSrc1 * CoefA1;
  285.  
  286.     /* - pSrc[2 * i] * CoefA2 */
  287.     outI = -(*pSrc1++) * CoefA2;
  288.  
  289.     /* (pSrc[2 * i + 1] + pSrc[2 * fftLen - 2 * i + 1]) * CoefA2 */
  290.     outR += (*pSrc1 + *pSrc2) * CoefA2;
  291.  
  292.     /* pSrc[2 * i + 1] * CoefA1 */
  293.     outI += (*pSrc1++) * CoefA1;
  294.  
  295.     CoefB1 = *pCoefB;
  296.  
  297.     /* - pSrc[2 * fftLen - 2 * i + 1] * CoefB1 */
  298.     outI -= *pSrc2-- * CoefB1;
  299.  
  300.     /* pSrc[2 * fftLen - 2 * i] * CoefB1 */
  301.     outR += *pSrc2 * CoefB1;
  302.  
  303.     /* pSrc[2 * fftLen - 2 * i] * CoefA2 */
  304.     outI += *pSrc2-- * CoefA2;
  305.  
  306.     /* write output */
  307.     *pDst++ = outR;
  308.     *pDst++ = outI;
  309.  
  310.     /* update coefficient pointer */
  311.     pCoefB = pCoefB + (modifier * 2U);
  312.     pCoefA = pCoefA + ((modifier * 2U) - 1U);
  313.  
  314.     /* Decrement loop count */
  315.     fftLen--;
  316.   }
  317.  
  318. }
  319.