WebSVN – dashGPS – Blame – /trunk/Drivers/CMSIS/DSP/Source/TransformFunctions/arm_rfft_init_f32.c

Rev	Author	Line No.	Line
2	mjames	1	/* ----------------------------------------------------------------------
		2	* Project: CMSIS DSP Library
		3	* Title: arm_rfft_init_f32.c
		4	* Description: RFFT & RIFFT Floating point 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
		31	/**
		32	* @ingroup RealFFT
		33	*/
		34
		35	/**
		36	* @addtogroup RealFFT_Table Real FFT Tables
		37	* @{
		38	*/
		39
		40	/**
		41	* \par
		42	* Generation of realCoefA array:
		43	* \par
		44	* n = 4096
		45	* <pre>for (i = 0; i < n; i++)
		46	* {
		47	* pATable[2 * i] = 0.5 * (1.0 - sin (2 * PI / (double) (2 * n) * (double) i));
		48	* pATable[2 * i + 1] = 0.5 * (-1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
		49	* } </pre>
		50	//*
		51	* \par
		52	* Generation of realCoefB array:
		53	* \par
		54	* n = 4096
		55	* <pre>for (i = 0; i < n; i++)
		56	* {
		57	* pBTable[2 * i] = 0.5 * (1.0 + sin (2 * PI / (double) (2 * n) * (double) i));
		58	* pBTable[2 * i + 1] = 0.5 * (1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
		59	* } </pre>
		60	*
		61	//*
		62	* @brief Initialization function for the floating-point RFFT/RIFFT.
		63	* @deprecated Do not use this function. It has been superceded by \ref arm_rfft_fast_init_f32 and will be removed
		64	* in the future.
		65	* @param[in,out] *S points to an instance of the floating-point RFFT/RIFFT structure.
		66	* @param[in,out] *S_CFFT points to an instance of the floating-point CFFT/CIFFT structure.
		67	* @param[in] fftLenReal length of the FFT.
		68	* @param[in] ifftFlagR flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform.
		69	* @param[in] bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
		70	* @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.
		71	*
		72	* \par Description:
		73	* \par
		74	* The parameter <code>fftLenReal</code> Specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 128, 512, 2048.
		75	* \par
		76	* The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed.
		77	* Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated.
		78	* \par
		79	* The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order.
		80	* Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.
		81	* \par
		82	* This function also initializes Twiddle factor table.
		83	*/
		84
		85	/**
		86	* @} end of RealFFT_Table group
		87	*/
		88
		89	/**
		90	* @addtogroup RealFFT
		91	* @{
		92	*/
		93
		94	arm_status arm_rfft_init_f32(
		95	arm_rfft_instance_f32 * S,
		96	arm_cfft_radix4_instance_f32 * S_CFFT,
		97	uint32_t fftLenReal,
		98	uint32_t ifftFlagR,
		99	uint32_t bitReverseFlag)
		100	{
		101
		102	/* Initialise the default arm status */
		103	arm_status status = ARM_MATH_SUCCESS;
		104
		105	/* Initialize the Real FFT length */
		106	S->fftLenReal = (uint16_t) fftLenReal;
		107
		108	/* Initialize the Complex FFT length */
		109	S->fftLenBy2 = (uint16_t) fftLenReal / 2U;
		110
		111	/* Initialize the Twiddle coefficientA pointer */
		112	S->pTwiddleAReal = (float32_t *) realCoefA;
		113
		114	/* Initialize the Twiddle coefficientB pointer */
		115	S->pTwiddleBReal = (float32_t *) realCoefB;
		116
		117	/* Initialize the Flag for selection of RFFT or RIFFT */
		118	S->ifftFlagR = (uint8_t) ifftFlagR;
		119
		120	/* Initialize the Flag for calculation Bit reversal or not */
		121	S->bitReverseFlagR = (uint8_t) bitReverseFlag;
		122
		123	/* Initializations of structure parameters depending on the FFT length */
		124	switch (S->fftLenReal)
		125	{
		126	/* Init table modifier value */
		127	case 8192U:
		128	S->twidCoefRModifier = 1U;
		129	break;
		130	case 2048U:
		131	S->twidCoefRModifier = 4U;
		132	break;
		133	case 512U:
		134	S->twidCoefRModifier = 16U;
		135	break;
		136	case 128U:
		137	S->twidCoefRModifier = 64U;
		138	break;
		139	default:
		140	/* Reporting argument error if rfftSize is not valid value */
		141	status = ARM_MATH_ARGUMENT_ERROR;
		142	break;
		143	}
		144
		145	/* Init Complex FFT Instance */
		146	S->pCfft = S_CFFT;
		147
		148	if (S->ifftFlagR)
		149	{
		150	/* Initializes the CIFFT Module for fftLenreal/2 length */
		151	arm_cfft_radix4_init_f32(S->pCfft, S->fftLenBy2, 1U, 0U);
		152	}
		153	else
		154	{
		155	/* Initializes the CFFT Module for fftLenreal/2 length */
		156	arm_cfft_radix4_init_f32(S->pCfft, S->fftLenBy2, 0U, 0U);
		157	}
		158
		159	/* return the status of RFFT Init function */
		160	return (status);
		161
		162	}
		163
		164	/**
		165	* @} end of RealFFT group
		166	*/
		167
		168

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