File content as of revision 1:fdd22bb7aa52:

/* ----------------------------------------------------------------------    
* Copyright (C) 2010 ARM Limited. All rights reserved.    
*    
* $Date:        15. February 2012  
* $Revision:     V1.1.0  
*    
* Project:         CMSIS DSP Library    
* Title:        arm_cfft_radix4_init_f32.c    
*    
* Description:    Radix-4 Decimation in Frequency Floating-point CFFT & CIFFT Initialization function    
*    
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*  
* Version 1.1.0 2012/02/15 
*    Updated with more optimizations, bug fixes and minor API changes.  
*   
* Version 1.0.10 2011/7/15  
*    Big Endian support added and Merged M0 and M3/M4 Source code.   
*    
* Version 1.0.3 2010/11/29   
*    Re-organized the CMSIS folders and updated documentation.    
*     
* Version 1.0.2 2010/11/11    
*    Documentation updated.     
*    
* Version 1.0.1 2010/10/05     
*    Production release and review comments incorporated.    
*    
* Version 1.0.0 2010/09/20     
*    Production release and review comments incorporated.    
*    
* Version 0.0.5  2010/04/26     
*      incorporated review comments and updated with latest CMSIS layer    
*    
* Version 0.0.3  2010/03/10     
*    Initial version    
* -------------------------------------------------------------------- */


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

/**    
 * @ingroup groupTransforms    
 */

/**    
 * @addtogroup Radix4_CFFT_CIFFT    
 * @{    
 */

/**    
* @brief  Initialization function for the floating-point CFFT/CIFFT.   
* @param[in,out] *S             points to an instance of the floating-point CFFT/CIFFT structure.   
* @param[in]     fftLen         length of the FFT.   
* @param[in]     ifftFlag       flag that selects forward (ifftFlag=0) or inverse (ifftFlag=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>fftLen</code> is not a supported value.   
*    
* \par Description:   
* \par    
* The parameter <code>ifftFlag</code> controls whether a forward or inverse transform is computed.    
* Set(=1) ifftFlag for calculation of CIFFT otherwise  CFFT 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    
* The parameter <code>fftLen</code>    Specifies length of CFFT/CIFFT process. Supported FFT Lengths are 16, 64, 256, 1024.    
* \par    
* This Function also initializes Twiddle factor table pointer and Bit reversal table pointer.    
*/

arm_status arm_cfft_radix4_init_f32(
  arm_cfft_radix4_instance_f32 * 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 = (float32_t *) twiddleCoef;

  /*  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;
    /*  Initialise the 1/fftLen Value */
    S->onebyfftLen = 0.000244140625;
    break;

  case 1024u:
    /*  Initializations of structure parameters for 1024 point FFT */

    /*  Initialise the twiddle coef modifier value */
    S->twidCoefModifier = 4u;
    /*  Initialise the bit reversal table modifier */
    S->bitRevFactor = 4u;
    /*  Initialise the bit reversal table pointer */
    S->pBitRevTable = (uint16_t *) & armBitRevTable[3];
    /*  Initialise the 1/fftLen Value */
    S->onebyfftLen = 0.0009765625f;
    break;


  case 256u:
    /*  Initializations of structure parameters for 256 point FFT */
    S->twidCoefModifier = 16u;
    S->bitRevFactor = 16u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[15];
    S->onebyfftLen = 0.00390625f;
    break;

  case 64u:
    /*  Initializations of structure parameters for 64 point FFT */
    S->twidCoefModifier = 64u;
    S->bitRevFactor = 64u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[63];
    S->onebyfftLen = 0.015625f;
    break;

  case 16u:
    /*  Initializations of structure parameters for 16 point FFT */
    S->twidCoefModifier = 256u;
    S->bitRevFactor = 256u;
    S->pBitRevTable = (uint16_t *) & armBitRevTable[255];
    S->onebyfftLen = 0.0625f;
    break;


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

  return (status);
}

/**    
 * @} end of Radix4_CFFT_CIFFT group    
 */