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| 56 | mjames | 1 | /* ---------------------------------------------------------------------- |
| 2 | * Project: CMSIS DSP Library |
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| 3 | * Title: arm_rfft_init_q31.c |
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| 4 | * Description: RFFT & RIFFT Q31 initialisation function |
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| 5 | * |
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| 6 | * $Date: 27. January 2017 |
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| 7 | * $Revision: V.1.5.1 |
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| 8 | * |
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| 9 | * Target Processor: Cortex-M cores |
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| 10 | * -------------------------------------------------------------------- */ |
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| 11 | /* |
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| 12 | * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. |
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| 13 | * |
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| 14 | * SPDX-License-Identifier: Apache-2.0 |
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| 15 | * |
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| 16 | * Licensed under the Apache License, Version 2.0 (the License); you may |
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| 17 | * not use this file except in compliance with the License. |
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| 18 | * You may obtain a copy of the License at |
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| 19 | * |
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| 20 | * www.apache.org/licenses/LICENSE-2.0 |
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| 21 | * |
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| 22 | * Unless required by applicable law or agreed to in writing, software |
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| 23 | * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
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| 24 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 25 | * See the License for the specific language governing permissions and |
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| 26 | * limitations under the License. |
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| 27 | */ |
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| 28 | |||
| 29 | #include "arm_math.h" |
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| 30 | #include "arm_common_tables.h" |
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| 31 | #include "arm_const_structs.h" |
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| 32 | |||
| 33 | /** |
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| 34 | * @ingroup RealFFT |
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| 35 | */ |
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| 36 | |||
| 37 | /** |
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| 38 | * @addtogroup RealFFT_Table Real FFT Tables |
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| 39 | * @{ |
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| 40 | */ |
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| 41 | |||
| 42 | /** |
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| 43 | * \par |
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| 44 | * Generation fixed-point realCoefAQ31 array in Q31 format: |
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| 45 | * \par |
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| 46 | * n = 4096 |
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| 47 | * <pre>for (i = 0; i < n; i++) |
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| 48 | * { |
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| 49 | * pATable[2 * i] = 0.5 * (1.0 - sin (2 * PI / (double) (2 * n) * (double) i)); |
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| 50 | * pATable[2 * i + 1] = 0.5 * (-1.0 * cos (2 * PI / (double) (2 * n) * (double) i)); |
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| 51 | * }</pre> |
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| 52 | * \par |
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| 53 | * Convert to fixed point Q31 format |
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| 54 | * round(pATable[i] * pow(2, 31)) |
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| 55 | *//** |
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| 56 | * \par |
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| 57 | * Generation of realCoefBQ31 array: |
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| 58 | * \par |
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| 59 | * n = 4096 |
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| 60 | * <pre>for (i = 0; i < n; i++) |
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| 61 | * { |
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| 62 | * pBTable[2 * i] = 0.5 * (1.0 + sin (2 * PI / (double) (2 * n) * (double) i)); |
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| 63 | * pBTable[2 * i + 1] = 0.5 * (1.0 * cos (2 * PI / (double) (2 * n) * (double) i)); |
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| 64 | * } </pre> |
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| 65 | * \par |
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| 66 | * Convert to fixed point Q31 format |
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| 67 | * round(pBTable[i] * pow(2, 31)) |
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| 68 | * |
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| 69 | *//** |
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| 70 | * @} end of RealFFT_Table group |
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| 71 | */ |
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| 72 | |||
| 73 | /** |
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| 74 | * @addtogroup RealFFT |
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| 75 | * @{ |
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| 76 | */ |
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| 77 | |||
| 78 | /** |
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| 79 | * @brief Initialization function for the Q31 RFFT/RIFFT. |
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| 80 | * @param[in, out] *S points to an instance of the Q31 RFFT/RIFFT structure. |
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| 81 | * @param[in] fftLenReal length of the FFT. |
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| 82 | * @param[in] ifftFlagR flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform. |
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| 83 | * @param[in] bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output. |
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| 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. |
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| 85 | * |
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| 86 | * \par Description: |
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| 87 | * \par |
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| 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. |
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| 89 | * \par |
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| 90 | * The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed. |
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| 91 | * Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated. |
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| 92 | * \par |
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| 93 | * The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order. |
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| 94 | * Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order. |
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| 95 | * \par 7 |
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| 96 | * This function also initializes Twiddle factor table. |
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| 97 | */ |
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| 98 | |||
| 99 | arm_status arm_rfft_init_q31( |
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| 100 | arm_rfft_instance_q31 * S, |
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| 101 | uint32_t fftLenReal, |
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| 102 | uint32_t ifftFlagR, |
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| 103 | uint32_t bitReverseFlag) |
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| 104 | { |
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| 105 | /* Initialise the default arm status */ |
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| 106 | arm_status status = ARM_MATH_SUCCESS; |
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| 107 | |||
| 108 | /* Initialize the Real FFT length */ |
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| 109 | S->fftLenReal = (uint16_t) fftLenReal; |
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| 110 | |||
| 111 | /* Initialize the Twiddle coefficientA pointer */ |
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| 112 | S->pTwiddleAReal = (q31_t *) realCoefAQ31; |
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| 113 | |||
| 114 | /* Initialize the Twiddle coefficientB pointer */ |
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| 115 | S->pTwiddleBReal = (q31_t *) realCoefBQ31; |
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| 116 | |||
| 117 | /* Initialize the Flag for selection of RFFT or RIFFT */ |
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| 118 | S->ifftFlagR = (uint8_t) ifftFlagR; |
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| 119 | |||
| 120 | /* Initialize the Flag for calculation Bit reversal or not */ |
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| 121 | S->bitReverseFlagR = (uint8_t) bitReverseFlag; |
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| 122 | |||
| 123 | /* Initialization of coef modifier depending on the FFT length */ |
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| 124 | switch (S->fftLenReal) |
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| 125 | { |
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| 126 | case 8192U: |
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| 127 | S->twidCoefRModifier = 1U; |
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| 128 | S->pCfft = &arm_cfft_sR_q31_len4096; |
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| 129 | break; |
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| 130 | case 4096U: |
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| 131 | S->twidCoefRModifier = 2U; |
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| 132 | S->pCfft = &arm_cfft_sR_q31_len2048; |
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| 133 | break; |
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| 134 | case 2048U: |
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| 135 | S->twidCoefRModifier = 4U; |
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| 136 | S->pCfft = &arm_cfft_sR_q31_len1024; |
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| 137 | break; |
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| 138 | case 1024U: |
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| 139 | S->twidCoefRModifier = 8U; |
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| 140 | S->pCfft = &arm_cfft_sR_q31_len512; |
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| 141 | break; |
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| 142 | case 512U: |
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| 143 | S->twidCoefRModifier = 16U; |
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| 144 | S->pCfft = &arm_cfft_sR_q31_len256; |
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| 145 | break; |
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| 146 | case 256U: |
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| 147 | S->twidCoefRModifier = 32U; |
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| 148 | S->pCfft = &arm_cfft_sR_q31_len128; |
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| 149 | break; |
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| 150 | case 128U: |
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| 151 | S->twidCoefRModifier = 64U; |
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| 152 | S->pCfft = &arm_cfft_sR_q31_len64; |
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| 153 | break; |
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| 154 | case 64U: |
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| 155 | S->twidCoefRModifier = 128U; |
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| 156 | S->pCfft = &arm_cfft_sR_q31_len32; |
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| 157 | break; |
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| 158 | case 32U: |
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| 159 | S->twidCoefRModifier = 256U; |
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| 160 | S->pCfft = &arm_cfft_sR_q31_len16; |
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| 161 | break; |
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| 162 | default: |
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| 163 | /* Reporting argument error if rfftSize is not valid value */ |
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| 164 | status = ARM_MATH_ARGUMENT_ERROR; |
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| 165 | break; |
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| 166 | } |
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| 167 | |||
| 168 | /* return the status of RFFT Init function */ |
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| 169 | return (status); |
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| 170 | } |
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| 171 | |||
| 172 | /** |
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| 173 | * @} end of RealFFT group |
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| 174 | */ |
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| 175 | |||
| 176 |