arm_cfft_radix2_init_q15.c

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/* ----------------------------------------------------------------------    
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
*    
* $Date:        19. March 2015
* $Revision:    V.1.4.5   
*    
* Project:      CMSIS DSP Library    
* Title:        arm_cfft_radix2_init_q15.c    
*    
* Description:  Radix-2 Decimation in Frequency Q15 FFT & IFFT initialization 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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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.     
* -------------------------------------------------------------------- */

#include "arm_math.h"
#include "arm_common_tables.h"

arm_status arm_cfft_radix2_init_q15(
  arm_cfft_radix2_instance_q15 * S,
  uint16_t fftLen,
  uint8_t ifftFlag,
  uint8_t bitReverseFlag)
{
  /*  Initialise the default arm status */
  arm_status status = ARM_MATH_SUCCESS;

  /*  Initialise the FFT length */
  S->fftLen = fftLen;

  /*  Initialise the Twiddle coefficient pointer */
  S->pTwiddle = (q15_t *) twiddleCoef_4096_q15;
  /*  Initialise the Flag for selection of CFFT or CIFFT */
  S->ifftFlag = ifftFlag;
  /*  Initialise the Flag for calculation Bit reversal or not */
  S->bitReverseFlag = bitReverseFlag;

  /*  Initializations of structure parameters depending on the FFT length */
  switch (S->fftLen)
  {
  case 4096u:
    /*  Initializations of structure parameters for 4096 point FFT */

    /*  Initialise the twiddle coef modifier value */
    S->twidCoefModifier = 1u;
    /*  Initialise the bit reversal table modifier */
    S->bitRevFactor = 1u;
    /*  Initialise the bit reversal table pointer */
    S->pBitRevTable = (uint16_t *) armBitRevTable;

    break;

  case 2048u:
    /*  Initializations of structure parameters for 2048 point FFT */

    /*  Initialise the twiddle coef modifier value */
    S->twidCoefModifier = 2u;
    /*  Initialise the bit reversal table modifier */
    S->bitRevFactor = 2u;
    /*  Initialise the bit reversal table pointer */
    S->pBitRevTable = (uint16_t *) & armBitRevTable[1];

    break;

  case 1024u:
    /*  Initializations of structure parameters for 1024 point FFT */
    S->twidCoefModifier = 4u;
    S->bitRevFactor = 4u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[3];

    break;

  case 512u:
    /*  Initializations of structure parameters for 512 point FFT */
    S->twidCoefModifier = 8u;
    S->bitRevFactor = 8u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[7];

    break;

  case 256u:
    /*  Initializations of structure parameters for 256 point FFT */
    S->twidCoefModifier = 16u;
    S->bitRevFactor = 16u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[15];

    break;

  case 128u:
    /*  Initializations of structure parameters for 128 point FFT */
    S->twidCoefModifier = 32u;
    S->bitRevFactor = 32u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[31];

    break;

  case 64u:
    /*  Initializations of structure parameters for 64 point FFT */
    S->twidCoefModifier = 64u;
    S->bitRevFactor = 64u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[63];

    break;

  case 32u:
    /*  Initializations of structure parameters for 32 point FFT */
    S->twidCoefModifier = 128u;
    S->bitRevFactor = 128u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[127];

    break;

  case 16u:
    /*  Initializations of structure parameters for 16 point FFT */
    S->twidCoefModifier = 256u;
    S->bitRevFactor = 256u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[255];

    break;

  default:
    /*  Reporting argument error if fftSize is not valid value */
    status = ARM_MATH_ARGUMENT_ERROR;
    break;
  }

  return (status);
}