/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date: 19. March 2015
* $Revision: V.1.4.5
*
* Project: CMSIS DSP Library
* Title: arm_rfft_init_q15.c
*
* Description: RFFT & RIFFT Q15 initialisation function
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* - Neither the name of ARM LIMITED nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */
#include "arm_math.h"
#include "arm_common_tables.h"
#include "arm_const_structs.h"
/**
* @ingroup groupTransforms
*/
/**
* @addtogroup RealFFT
* @{
*/
/**
* \par
* Generation fixed-point realCoefAQ15 array in Q15 format:
* \par
* n = 4096
* <pre>for (i = 0; i < n; i++)
* {
* pATable[2 * i] = 0.5 * (1.0 - sin (2 * PI / (double) (2 * n) * (double) i));
* pATable[2 * i + 1] = 0.5 * (-1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
* } </pre>
* \par
* Convert to fixed point Q15 format
* round(pATable[i] * pow(2, 15))
*//**
* \par
* Generation of real_CoefB array:
* \par
* n = 4096
* <pre>for (i = 0; i < n; i++)
* {
* pBTable[2 * i] = 0.5 * (1.0 + sin (2 * PI / (double) (2 * n) * (double) i));
* pBTable[2 * i + 1] = 0.5 * (1.0 * cos (2 * PI / (double) (2 * n) * (double) i));
* } </pre>
* \par
* Convert to fixed point Q15 format
* round(pBTable[i] * pow(2, 15))
*
*//**
* @brief Initialization function for the Q15 RFFT/RIFFT.
* @param[in, out] *S points to an instance of the Q15 RFFT/RIFFT structure.
* @param[in] fftLenReal length of the FFT.
* @param[in] ifftFlagR flag that selects forward (ifftFlagR=0) or inverse (ifftFlagR=1) transform.
* @param[in] bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
* @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.
*
* \par Description:
* \par
* The parameter <code>fftLenReal</code> Specifies length of RFFT/RIFFT Process. Supported FFT Lengths are 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192.
* \par
* The parameter <code>ifftFlagR</code> controls whether a forward or inverse transform is computed.
* Set(=1) ifftFlagR to calculate RIFFT, otherwise RFFT is calculated.
* \par
* The parameter <code>bitReverseFlag</code> controls whether output is in normal order or bit reversed order.
* Set(=1) bitReverseFlag for output to be in normal order otherwise output is in bit reversed order.
* \par
* This function also initializes Twiddle factor table.
*/
arm_status arm_rfft_init_q15(
arm_rfft_instance_q15 * S,
uint32_t fftLenReal,
uint32_t ifftFlagR,
uint32_t bitReverseFlag)
{
/* Initialise the default arm status */
arm_status status = ARM_MATH_SUCCESS;
/* Initialize the Real FFT length */
S->fftLenReal = (uint16_t) fftLenReal;
/* Initialize the Twiddle coefficientA pointer */
S->pTwiddleAReal = (q15_t *) realCoefAQ15;
/* Initialize the Twiddle coefficientB pointer */
S->pTwiddleBReal = (q15_t *) realCoefBQ15;
/* Initialize the Flag for selection of RFFT or RIFFT */
S->ifftFlagR = (uint8_t) ifftFlagR;
/* Initialize the Flag for calculation Bit reversal or not */
S->bitReverseFlagR = (uint8_t) bitReverseFlag;
/* Initialization of coef modifier depending on the FFT length */
switch (S->fftLenReal)
{
case 8192u:
S->twidCoefRModifier = 1u;
S->pCfft = &arm_cfft_sR_q15_len4096;
break;
case 4096u:
S->twidCoefRModifier = 2u;
S->pCfft = &arm_cfft_sR_q15_len2048;
break;
case 2048u:
S->twidCoefRModifier = 4u;
S->pCfft = &arm_cfft_sR_q15_len1024;
break;
case 1024u:
S->twidCoefRModifier = 8u;
S->pCfft = &arm_cfft_sR_q15_len512;
break;
case 512u:
S->twidCoefRModifier = 16u;
S->pCfft = &arm_cfft_sR_q15_len256;
break;
case 256u:
S->twidCoefRModifier = 32u;
S->pCfft = &arm_cfft_sR_q15_len128;
break;
case 128u:
S->twidCoefRModifier = 64u;
S->pCfft = &arm_cfft_sR_q15_len64;
break;
case 64u:
S->twidCoefRModifier = 128u;
S->pCfft = &arm_cfft_sR_q15_len32;
break;
case 32u:
S->twidCoefRModifier = 256u;
S->pCfft = &arm_cfft_sR_q15_len16;
break;
default:
/* Reporting argument error if rfftSize is not valid value */
status = ARM_MATH_ARGUMENT_ERROR;
break;
}
/* return the status of RFFT Init function */
return (status);
}
/**
* @} end of RealFFT group
*/