1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_cfft_radix2_init_q31.c
10 * Description: Radix-2 Decimation in Frequency Fixed-point CFFT & CIFFT Initialization function
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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15 * modification, are permitted provided that the following conditions
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27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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39 * -------------------------------------------------------------------- */
43 #include "arm_common_tables.h"
46 * @ingroup groupTransforms
50 * @addtogroup ComplexFFT
57 * @brief Initialization function for the Q31 CFFT/CIFFT.
58 * @param[in,out] *S points to an instance of the Q31 CFFT/CIFFT structure.
59 * @param[in] fftLen length of the FFT.
60 * @param[in] ifftFlag flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.
61 * @param[in] bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
62 * @return The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if <code>fftLen</code> is not a supported value.
66 * The parameter <code>ifftFlag</code> controls whether a forward or inverse transform is computed.
67 * Set(=1) ifftFlag for calculation of CIFFT otherwise CFFT is calculated
69 * The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order.
70 * Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.
72 * The parameter <code>fftLen</code> Specifies length of CFFT/CIFFT process. Supported FFT Lengths are 16, 64, 256, 1024.
74 * This Function also initializes Twiddle factor table pointer and Bit reversal table pointer.
77 arm_status arm_cfft_radix2_init_q31(
78 arm_cfft_radix2_instance_q31 * S,
81 uint8_t bitReverseFlag)
83 /* Initialise the default arm status */
84 arm_status status = ARM_MATH_SUCCESS;
86 /* Initialise the FFT length */
89 /* Initialise the Twiddle coefficient pointer */
90 S->pTwiddle = (q31_t *) twiddleCoefQ31;
91 /* Initialise the Flag for selection of CFFT or CIFFT */
92 S->ifftFlag = ifftFlag;
93 /* Initialise the Flag for calculation Bit reversal or not */
94 S->bitReverseFlag = bitReverseFlag;
96 /* Initializations of Instance structure depending on the FFT length */
99 /* Initializations of structure parameters for 4096 point FFT */
101 /* Initialise the twiddle coef modifier value */
102 S->twidCoefModifier = 1u;
103 /* Initialise the bit reversal table modifier */
104 S->bitRevFactor = 1u;
105 /* Initialise the bit reversal table pointer */
106 S->pBitRevTable = (uint16_t *) armBitRevTable;
109 /* Initializations of structure parameters for 2048 point FFT */
111 /* Initialise the twiddle coef modifier value */
112 S->twidCoefModifier = 2u;
113 /* Initialise the bit reversal table modifier */
114 S->bitRevFactor = 2u;
115 /* Initialise the bit reversal table pointer */
116 S->pBitRevTable = (uint16_t *) & armBitRevTable[1];
119 /* Initializations of structure parameters for 1024 point FFT */
121 /* Initialise the twiddle coef modifier value */
122 S->twidCoefModifier = 4u;
123 /* Initialise the bit reversal table modifier */
124 S->bitRevFactor = 4u;
125 /* Initialise the bit reversal table pointer */
126 S->pBitRevTable = (uint16_t *) & armBitRevTable[3];
129 /* Initializations of structure parameters for 512 point FFT */
131 /* Initialise the twiddle coef modifier value */
132 S->twidCoefModifier = 8u;
133 /* Initialise the bit reversal table modifier */
134 S->bitRevFactor = 8u;
135 /* Initialise the bit reversal table pointer */
136 S->pBitRevTable = (uint16_t *) & armBitRevTable[7];
140 /* Initializations of structure parameters for 256 point FFT */
141 S->twidCoefModifier = 16u;
142 S->bitRevFactor = 16u;
143 S->pBitRevTable = (uint16_t *) & armBitRevTable[15];
147 /* Initializations of structure parameters for 128 point FFT */
148 S->twidCoefModifier = 32u;
149 S->bitRevFactor = 32u;
150 S->pBitRevTable = (uint16_t *) & armBitRevTable[31];
154 /* Initializations of structure parameters for 64 point FFT */
155 S->twidCoefModifier = 64u;
156 S->bitRevFactor = 64u;
157 S->pBitRevTable = (uint16_t *) & armBitRevTable[63];
161 /* Initializations of structure parameters for 32 point FFT */
162 S->twidCoefModifier = 128u;
163 S->bitRevFactor = 128u;
164 S->pBitRevTable = (uint16_t *) & armBitRevTable[127];
168 /* Initializations of structure parameters for 16 point FFT */
169 S->twidCoefModifier = 256u;
170 S->bitRevFactor = 256u;
171 S->pBitRevTable = (uint16_t *) & armBitRevTable[255];
176 /* Reporting argument error if fftSize is not valid value */
177 status = ARM_MATH_ARGUMENT_ERROR;
185 * @} end of ComplexFFT group