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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_rfft_init_q15.c
  4.  * Description:  RFFT & RIFFT Q15 initialisation 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. #include "arm_common_tables.h"
  31. #include "arm_const_structs.h"
  32.  
  33. /**
  34. * @ingroup RealFFT
  35. */
  36.  
  37. /**
  38.  * @addtogroup RealFFT_Table Real FFT Tables
  39. * @{
  40. */
  41.  
  42. /**
  43. * \par
  44. * Generation fixed-point realCoefAQ15 array in Q15 format:
  45. * \par
  46. * n = 4096
  47. * <pre>for (i = 0; i < n; i++)
  48. *  {
  49. *    pATable[2 * i] = 0.5 * (1.0 - sin (2 * PI / (double) (2 * n) * (double) i));
  50. *    pATable[2 * i + 1] = 0.5 * (-1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
  51. *  } </pre>
  52. * \par
  53. * Convert to fixed point Q15 format
  54. *       round(pATable[i] * pow(2, 15))
  55. *//**
  56. * \par
  57. * Generation of real_CoefB array:
  58. * \par
  59. * n = 4096
  60. * <pre>for (i = 0; i < n; i++)
  61. *  {
  62. *    pBTable[2 * i] = 0.5 * (1.0 + sin (2 * PI / (double) (2 * n) * (double) i));
  63. *    pBTable[2 * i + 1] = 0.5 * (1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
  64. *  } </pre>
  65. * \par
  66. * Convert to fixed point Q15 format
  67. *       round(pBTable[i] * pow(2, 15))
  68. *
  69. *//**
  70. * @} end of RealFFT_Table group
  71. */
  72.  
  73. /**
  74. * @addtogroup RealFFT
  75. * @{
  76. */
  77.  
  78. /**
  79. * @brief  Initialization function for the Q15 RFFT/RIFFT.
  80. * @param[in, out] *S             points to an instance of the Q15 RFFT/RIFFT structure.
  81. * @param[in]      fftLenReal     length of the FFT.
  82. * @param[in]      ifftFlagR      flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform.
  83. * @param[in]      bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
  84. * @return         The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLenReal</code> is not a supported value.
  85. *
  86. * \par Description:
  87. * \par
  88. * The parameter <code>fftLenReal</code> Specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192.
  89. * \par
  90. * The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed.
  91. * Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated.
  92. * \par
  93. * The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order.
  94. * Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.
  95. * \par
  96. * This function also initializes Twiddle factor table.
  97. */
  98. arm_status arm_rfft_init_q15(
  99.     arm_rfft_instance_q15 * S,
  100.     uint32_t fftLenReal,
  101.     uint32_t ifftFlagR,
  102.     uint32_t bitReverseFlag)
  103. {
  104.     /*  Initialise the default arm status */
  105.     arm_status status = ARM_MATH_SUCCESS;
  106.  
  107.     /*  Initialize the Real FFT length */
  108.     S->fftLenReal = (uint16_t) fftLenReal;
  109.  
  110.     /*  Initialize the Twiddle coefficientA pointer */
  111.     S->pTwiddleAReal = (q15_t *) realCoefAQ15;
  112.  
  113.     /*  Initialize the Twiddle coefficientB pointer */
  114.     S->pTwiddleBReal = (q15_t *) realCoefBQ15;
  115.  
  116.     /*  Initialize the Flag for selection of RFFT or RIFFT */
  117.     S->ifftFlagR = (uint8_t) ifftFlagR;
  118.  
  119.     /*  Initialize the Flag for calculation Bit reversal or not */
  120.     S->bitReverseFlagR = (uint8_t) bitReverseFlag;
  121.  
  122.     /*  Initialization of coef modifier depending on the FFT length */
  123.     switch (S->fftLenReal)
  124.     {
  125.     case 8192U:
  126.         S->twidCoefRModifier = 1U;
  127.         S->pCfft = &arm_cfft_sR_q15_len4096;
  128.         break;
  129.     case 4096U:
  130.         S->twidCoefRModifier = 2U;
  131.         S->pCfft = &arm_cfft_sR_q15_len2048;
  132.         break;
  133.     case 2048U:
  134.         S->twidCoefRModifier = 4U;
  135.         S->pCfft = &arm_cfft_sR_q15_len1024;
  136.         break;
  137.     case 1024U:
  138.         S->twidCoefRModifier = 8U;
  139.         S->pCfft = &arm_cfft_sR_q15_len512;
  140.         break;
  141.     case 512U:
  142.         S->twidCoefRModifier = 16U;
  143.         S->pCfft = &arm_cfft_sR_q15_len256;
  144.         break;
  145.     case 256U:
  146.         S->twidCoefRModifier = 32U;
  147.         S->pCfft = &arm_cfft_sR_q15_len128;
  148.         break;
  149.     case 128U:
  150.         S->twidCoefRModifier = 64U;
  151.         S->pCfft = &arm_cfft_sR_q15_len64;
  152.         break;
  153.     case 64U:
  154.         S->twidCoefRModifier = 128U;
  155.         S->pCfft = &arm_cfft_sR_q15_len32;
  156.         break;
  157.     case 32U:
  158.         S->twidCoefRModifier = 256U;
  159.         S->pCfft = &arm_cfft_sR_q15_len16;
  160.         break;
  161.     default:
  162.         /*  Reporting argument error if rfftSize is not valid value */
  163.         status = ARM_MATH_ARGUMENT_ERROR;
  164.         break;
  165.     }
  166.  
  167.     /* return the status of RFFT Init function */
  168.     return (status);
  169. }
  170.  
  171. /**
  172. * @} end of RealFFT group
  173. */
  174.