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_radix4_init_q15.c
10 * Description: Radix-4 Decimation in Frequency Q15 FFT & IFFT 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 * -------------------------------------------------------------------- */
42 #include "arm_common_tables.h"
45 * @ingroup groupTransforms
50 * @addtogroup ComplexFFT
56 * @brief Initialization function for the Q15 CFFT/CIFFT.
57 * @param[in,out] *S points to an instance of the Q15 CFFT/CIFFT structure.
58 * @param[in] fftLen length of the FFT.
59 * @param[in] ifftFlag flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.
60 * @param[in] bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
61 * @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.
65 * The parameter <code>ifftFlag</code> controls whether a forward or inverse transform is computed.
66 * Set(=1) ifftFlag for calculation of CIFFT otherwise CFFT is calculated
68 * The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order.
69 * Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.
71 * The parameter <code>fftLen</code> Specifies length of CFFT/CIFFT process. Supported FFT Lengths are 16, 64, 256, 1024.
73 * This Function also initializes Twiddle factor table pointer and Bit reversal table pointer.
76 arm_status arm_cfft_radix4_init_q15(
77 arm_cfft_radix4_instance_q15 * S,
80 uint8_t bitReverseFlag)
82 /* Initialise the default arm status */
83 arm_status status = ARM_MATH_SUCCESS;
84 /* Initialise the FFT length */
86 /* Initialise the Twiddle coefficient pointer */
87 S->pTwiddle = (q15_t *) twiddleCoefQ15;
88 /* Initialise the Flag for selection of CFFT or CIFFT */
89 S->ifftFlag = ifftFlag;
90 /* Initialise the Flag for calculation Bit reversal or not */
91 S->bitReverseFlag = bitReverseFlag;
93 /* Initializations of structure parameters depending on the FFT length */
97 /* Initializations of structure parameters for 4096 point FFT */
99 /* Initialise the twiddle coef modifier value */
100 S->twidCoefModifier = 1u;
101 /* Initialise the bit reversal table modifier */
102 S->bitRevFactor = 1u;
103 /* Initialise the bit reversal table pointer */
104 S->pBitRevTable = (uint16_t *) armBitRevTable;
109 /* Initializations of structure parameters for 1024 point FFT */
110 S->twidCoefModifier = 4u;
111 S->bitRevFactor = 4u;
112 S->pBitRevTable = (uint16_t *) & armBitRevTable[3];
117 /* Initializations of structure parameters for 256 point FFT */
118 S->twidCoefModifier = 16u;
119 S->bitRevFactor = 16u;
120 S->pBitRevTable = (uint16_t *) & armBitRevTable[15];
125 /* Initializations of structure parameters for 64 point FFT */
126 S->twidCoefModifier = 64u;
127 S->bitRevFactor = 64u;
128 S->pBitRevTable = (uint16_t *) & armBitRevTable[63];
133 /* Initializations of structure parameters for 16 point FFT */
134 S->twidCoefModifier = 256u;
135 S->bitRevFactor = 256u;
136 S->pBitRevTable = (uint16_t *) & armBitRevTable[255];
141 /* Reporting argument error if fftSize is not valid value */
142 status = ARM_MATH_ARGUMENT_ERROR;
150 * @} end of ComplexFFT group