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_rfft_q15.c    
*    
* Description:    RFFT & RIFFT Q15 process 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 0.0.7  2010/06/10     
*    Misra-C changes done    
* -------------------------------------------------------------------- */


#include "arm_math.h"

/*--------------------------------------------------------------------    
*        Internal functions prototypes    
--------------------------------------------------------------------*/

void arm_split_rfft_q15(
  q15_t * pSrc,
  uint32_t fftLen,
  q15_t * pATable,
  q15_t * pBTable,
  q15_t * pDst,
  uint32_t modifier);

void arm_split_rifft_q15(
  q15_t * pSrc,
  uint32_t fftLen,
  q15_t * pATable,
  q15_t * pBTable,
  q15_t * pDst,
  uint32_t modifier);

/**    
 * @addtogroup RFFT_RIFFT    
 * @{    
 */

/**    
 * @brief Processing function for the Q15 RFFT/RIFFT.   
 * @param[in]  *S    points to an instance of the Q15 RFFT/RIFFT structure.   
 * @param[in]  *pSrc points to the input buffer.   
 * @param[out] *pDst points to the output buffer.   
 * @return none.   
 *    
 * \par Input an output formats:   
 * \par    
 * Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process.    
 * Hence the output format is different for different RFFT sizes.    
 * The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:   
 * \par    
 * \image html RFFTQ15.gif "Input and Output Formats for Q15 RFFT"    
 * \par    
 * \image html RIFFTQ15.gif "Input and Output Formats for Q15 RIFFT"    
 */

void arm_rfft_q15(
  const arm_rfft_instance_q15 * S,
  q15_t * pSrc,
  q15_t * pDst)
{
  const arm_cfft_radix4_instance_q15 *S_CFFT = S->pCfft;

  /* Calculation of RIFFT of input */
  if(S->ifftFlagR == 1u)
  {
    /*  Real IFFT core process */
    arm_split_rifft_q15(pSrc, S->fftLenBy2, S->pTwiddleAReal,
                        S->pTwiddleBReal, pDst, S->twidCoefRModifier);

    /* Complex readix-4 IFFT process */
    arm_radix4_butterfly_inverse_q15(pDst, S_CFFT->fftLen,
                                     S_CFFT->pTwiddle,
                                     S_CFFT->twidCoefModifier);

    /* Bit reversal process */
    if(S->bitReverseFlagR == 1u)
    {
      arm_bitreversal_q15(pDst, S_CFFT->fftLen,
                          S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
    }
  }
  else
  {
    /* Calculation of RFFT of input */

    /* Complex readix-4 FFT process */
    arm_radix4_butterfly_q15(pSrc, S_CFFT->fftLen,
                             S_CFFT->pTwiddle, S_CFFT->twidCoefModifier);

    /* Bit reversal process */
    if(S->bitReverseFlagR == 1u)
    {
      arm_bitreversal_q15(pSrc, S_CFFT->fftLen,
                          S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
    }

    arm_split_rfft_q15(pSrc, S->fftLenBy2, S->pTwiddleAReal,
                       S->pTwiddleBReal, pDst, S->twidCoefRModifier);
  }

}

  /**    
   * @} end of RFFT_RIFFT group    
   */

/**    
 * @brief  Core Real FFT process    
 * @param  *pSrc                 points to the input buffer.   
 * @param  fftLen                  length of FFT.   
 * @param  *pATable             points to the A twiddle Coef buffer.    
 * @param  *pBTable             points to the B twiddle Coef buffer.   
 * @param  *pDst                 points to the output buffer.   
 * @param  modifier             twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.   
 * @return none.    
 * The function implements a Real FFT    
 */

void arm_split_rfft_q15(
  q15_t * pSrc,
  uint32_t fftLen,
  q15_t * pATable,
  q15_t * pBTable,
  q15_t * pDst,
  uint32_t modifier)
{
  uint32_t i;                                    /* Loop Counter */
  q31_t outR, outI;                              /* Temporary variables for output */
  q15_t *pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */
  q15_t *pSrc1, *pSrc2;


//  pSrc[2u * fftLen] = pSrc[0]; 
//  pSrc[(2u * fftLen) + 1u] = pSrc[1]; 

  pCoefA = &pATable[modifier * 2u];
  pCoefB = &pBTable[modifier * 2u];

  pSrc1 = &pSrc[2];
  pSrc2 = &pSrc[(2u * fftLen) - 2u];

#ifndef ARM_MATH_CM0

  /* Run the below code for Cortex-M4 and Cortex-M3 */

  i = 1u;

  while(i < fftLen)
  {
    /*    
       outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]    
       + pSrc[2 * n - 2 * i] * pBTable[2 * i] +    
       pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    
     */

    /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +    
       pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */


#ifndef ARM_MATH_BIG_ENDIAN

    /* pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1] */
    outR = __SMUSD(*__SIMD32(pSrc1), *__SIMD32(pCoefA));

#else

    /* -(pSrc[2 * i + 1] * pATable[2 * i + 1] - pSrc[2 * i] * pATable[2 * i]) */
    outR = -(__SMUSD(*__SIMD32(pSrc1), *__SIMD32(pCoefA)));

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

    /* pSrc[2 * n - 2 * i] * pBTable[2 * i] +    
       pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]) */
    outR = __SMLAD(*__SIMD32(pSrc2), *__SIMD32(pCoefB), outR) >> 15u;

    /* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */

#ifndef ARM_MATH_BIG_ENDIAN

    outI = __SMUSDX(*__SIMD32(pSrc2)--, *__SIMD32(pCoefB));

#else

    outI = __SMUSDX(*__SIMD32(pCoefB), *__SIMD32(pSrc2)--);

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

    /* (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] */
    outI = __SMLADX(*__SIMD32(pSrc1)++, *__SIMD32(pCoefA), outI);

    /* write output */
    pDst[2u * i] = (q15_t) outR;
    pDst[(2u * i) + 1u] = outI >> 15u;

    /* write complex conjugate output */
    pDst[(4u * fftLen) - (2u * i)] = (q15_t) outR;
    pDst[((4u * fftLen) - (2u * i)) + 1u] = -(outI >> 15u);

    /* update coefficient pointer */
    pCoefB = pCoefB + (2u * modifier);
    pCoefA = pCoefA + (2u * modifier);

    i++;

  }

  pDst[2u * fftLen] = pSrc[0] - pSrc[1];
  pDst[(2u * fftLen) + 1u] = 0;

  pDst[0] = pSrc[0] + pSrc[1];
  pDst[1] = 0;


#else

  /* Run the below code for Cortex-M0 */

  i = 1u;

  while(i < fftLen)
  {
    /*    
       outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]    
       + pSrc[2 * n - 2 * i] * pBTable[2 * i] +    
       pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    
     */

    outR = *pSrc1 * *pCoefA;
    outR = outR - (*(pSrc1 + 1) * *(pCoefA + 1));
    outR = outR + (*pSrc2 * *pCoefB);
    outR = (outR + (*(pSrc2 + 1) * *(pCoefB + 1))) >> 15;


    /* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +    
       pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);   
     */

    outI = *pSrc2 * *(pCoefB + 1);
    outI = outI - (*(pSrc2 + 1) * *pCoefB);
    outI = outI + (*(pSrc1 + 1) * *pCoefA);
    outI = outI + (*pSrc1 * *(pCoefA + 1));

    /* update input pointers */
    pSrc1 += 2u;
    pSrc2 -= 2u;

    /* write output */
    pDst[2u * i] = (q15_t) outR;
    pDst[(2u * i) + 1u] = outI >> 15u;

    /* write complex conjugate output */
    pDst[(4u * fftLen) - (2u * i)] = (q15_t) outR;
    pDst[((4u * fftLen) - (2u * i)) + 1u] = -(outI >> 15u);

    /* update coefficient pointer */
    pCoefB = pCoefB + (2u * modifier);
    pCoefA = pCoefA + (2u * modifier);

    i++;

  }

  pDst[2u * fftLen] = pSrc[0] - pSrc[1];
  pDst[(2u * fftLen) + 1u] = 0;

  pDst[0] = pSrc[0] + pSrc[1];
  pDst[1] = 0;

#endif /* #ifndef ARM_MATH_CM0 */

}


/**    
 * @brief  Core Real IFFT process    
 * @param[in]   *pSrc                 points to the input buffer.    
 * @param[in]   fftLen              length of FFT.   
 * @param[in]   *pATable             points to the twiddle Coef A buffer.   
 * @param[in]   *pBTable             points to the twiddle Coef B buffer.    
 * @param[out]  *pDst                 points to the output buffer.   
 * @param[in]   modifier             twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.   
 * @return none.    
 * The function implements a Real IFFT    
 */
void arm_split_rifft_q15(
  q15_t * pSrc,
  uint32_t fftLen,
  q15_t * pATable,
  q15_t * pBTable,
  q15_t * pDst,
  uint32_t modifier)
{
  uint32_t i;                                    /* Loop Counter */
  q31_t outR, outI;                              /* Temporary variables for output */
  q15_t *pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */
  q15_t *pSrc1, *pSrc2;
  q15_t *pDst1 = &pDst[0];

  pCoefA = &pATable[0];
  pCoefB = &pBTable[0];

  pSrc1 = &pSrc[0];
  pSrc2 = &pSrc[2u * fftLen];

#ifndef ARM_MATH_CM0

  /* Run the below code for Cortex-M4 and Cortex-M3 */

  i = fftLen;

  while(i > 0u)
  {

    /*    
       outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +    
       pIn[2 * n - 2 * i] * pBTable[2 * i] -    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    

       outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -    
       pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);    

     */


#ifndef ARM_MATH_BIG_ENDIAN

    /* pIn[2 * n - 2 * i] * pBTable[2 * i] -    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]) */
    outR = __SMUSD(*__SIMD32(pSrc2), *__SIMD32(pCoefB));

#else

    /* -(-pIn[2 * n - 2 * i] * pBTable[2 * i] +  
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1])) */
    outR = -(__SMUSD(*__SIMD32(pSrc2), *__SIMD32(pCoefB)));

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

    /* pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +    
       pIn[2 * n - 2 * i] * pBTable[2 * i] */
    outR = __SMLAD(*__SIMD32(pSrc1), *__SIMD32(pCoefA), outR) >> 15u;

    /*    
       -pIn[2 * n - 2 * i] * pBTable[2 * i + 1] +    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
    outI = __SMUADX(*__SIMD32(pSrc2)--, *__SIMD32(pCoefB));

    /* pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] */

#ifndef ARM_MATH_BIG_ENDIAN

    outI = __SMLSDX(*__SIMD32(pCoefA), *__SIMD32(pSrc1)++, -outI);

#else

    outI = __SMLSDX(*__SIMD32(pSrc1)++, *__SIMD32(pCoefA), -outI);

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */
    /* write output */

#ifndef ARM_MATH_BIG_ENDIAN

    *__SIMD32(pDst1)++ = __PKHBT(outR, (outI >> 15u), 16);

#else

    *__SIMD32(pDst1)++ = __PKHBT((outI >> 15u), outR, 16);

#endif /*      #ifndef ARM_MATH_BIG_ENDIAN     */

    /* update coefficient pointer */
    pCoefB = pCoefB + (2u * modifier);
    pCoefA = pCoefA + (2u * modifier);

    i--;

  }


#else

  /* Run the below code for Cortex-M0 */

  i = fftLen;

  while(i > 0u)
  {

    /*    
       outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +    
       pIn[2 * n - 2 * i] * pBTable[2 * i] -    
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);    
     */

    outR = *pSrc2 * *pCoefB;
    outR = outR - (*(pSrc2 + 1) * *(pCoefB + 1));
    outR = outR + (*pSrc1 * *pCoefA);
    outR = (outR + (*(pSrc1 + 1) * *(pCoefA + 1))) >> 15;

    /*   
       outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -   
       pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -   
       pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);   
     */

    outI = *(pSrc1 + 1) * *pCoefA;
    outI = outI - (*pSrc1 * *(pCoefA + 1));
    outI = outI - (*pSrc2 * *(pCoefB + 1));
    outI = outI - (*(pSrc2 + 1) * *(pCoefB));

    /* update input pointers */
    pSrc1 += 2u;
    pSrc2 -= 2u;

    /* write output */
    *pDst1++ = (q15_t) outR;
    *pDst1++ = (q15_t) (outI >> 15);

    /* update coefficient pointer */
    pCoefB = pCoefB + (2u * modifier);
    pCoefA = pCoefA + (2u * modifier);

    i--;

  }

#endif /* #ifndef ARM_MATH_CM0 */

}