arm_cfft_radix2_q31.c

/* ----------------------------------------------------------------------   
* 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_q31.c   
*   
* Description:	Radix-2 Decimation in Frequency CFFT & CIFFT Fixed point processing 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
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*     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,
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* -------------------------------------------------------------------- */

#include "arm_math.h"

void arm_radix2_butterfly_q31(
  q31_t * pSrc,
  uint32_t fftLen,
  q31_t * pCoef,
  uint16_t twidCoefModifier);

void arm_radix2_butterfly_inverse_q31(
  q31_t * pSrc,
  uint32_t fftLen,
  q31_t * pCoef,
  uint16_t twidCoefModifier);

void arm_bitreversal_q31(
  q31_t * pSrc,
  uint32_t fftLen,
  uint16_t bitRevFactor,
  uint16_t * pBitRevTab);

/**   
* @ingroup groupTransforms   
*/

/**   
* @addtogroup ComplexFFT   
* @{   
*/

/**   
* @details   
* @brief Processing function for the fixed-point CFFT/CIFFT.  
* @deprecated Do not use this function.  It has been superseded by \ref arm_cfft_q31 and will be removed
* @param[in]      *S    points to an instance of the fixed-point CFFT/CIFFT structure.  
* @param[in, out] *pSrc points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.  
* @return none.  
*/

void arm_cfft_radix2_q31(
const arm_cfft_radix2_instance_q31 * S,
q31_t * pSrc)
{

   if(S->ifftFlag == 1u)
   {
      arm_radix2_butterfly_inverse_q31(pSrc, S->fftLen,
      S->pTwiddle, S->twidCoefModifier);
   }
   else
   {
      arm_radix2_butterfly_q31(pSrc, S->fftLen,
      S->pTwiddle, S->twidCoefModifier);
   }

   arm_bitreversal_q31(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
}

/**   
* @} end of ComplexFFT group   
*/

void arm_radix2_butterfly_q31(
q31_t * pSrc,
uint32_t fftLen,
q31_t * pCoef,
uint16_t twidCoefModifier)
{

   unsigned i, j, k, l, m;
   unsigned n1, n2, ia;
   q31_t xt, yt, cosVal, sinVal;
   q31_t p0, p1;

   //N = fftLen; 
   n2 = fftLen;

   n1 = n2;
   n2 = n2 >> 1;
   ia = 0;

   // loop for groups 
   for (i = 0; i < n2; i++)
   {
      cosVal = pCoef[ia * 2];
      sinVal = pCoef[(ia * 2) + 1];
      ia = ia + twidCoefModifier;

      l = i + n2;
      xt = (pSrc[2 * i] >> 1u) - (pSrc[2 * l] >> 1u);
      pSrc[2 * i] = ((pSrc[2 * i] >> 1u) + (pSrc[2 * l] >> 1u)) >> 1u;
      
      yt = (pSrc[2 * i + 1] >> 1u) - (pSrc[2 * l + 1] >> 1u);
      pSrc[2 * i + 1] =
        ((pSrc[2 * l + 1] >> 1u) + (pSrc[2 * i + 1] >> 1u)) >> 1u;

      mult_32x32_keep32_R(p0, xt, cosVal);
      mult_32x32_keep32_R(p1, yt, cosVal);
      multAcc_32x32_keep32_R(p0, yt, sinVal); 
      multSub_32x32_keep32_R(p1, xt, sinVal);
      
      pSrc[2u * l] = p0;
      pSrc[2u * l + 1u] = p1;

   }                             // groups loop end 

   twidCoefModifier <<= 1u;

   // loop for stage 
   for (k = fftLen / 2; k > 2; k = k >> 1)
   {
      n1 = n2;
      n2 = n2 >> 1;
      ia = 0;

      // loop for groups 
      for (j = 0; j < n2; j++)
      {
         cosVal = pCoef[ia * 2];
         sinVal = pCoef[(ia * 2) + 1];
         ia = ia + twidCoefModifier;

         // loop for butterfly 
         i = j;
         m = fftLen / n1;
         do
         {
            l = i + n2;
            xt = pSrc[2 * i] - pSrc[2 * l];
            pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]) >> 1u;
            
            yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
            pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]) >> 1u;

            mult_32x32_keep32_R(p0, xt, cosVal);
            mult_32x32_keep32_R(p1, yt, cosVal);
            multAcc_32x32_keep32_R(p0, yt, sinVal);
            multSub_32x32_keep32_R(p1, xt, sinVal);
            
            pSrc[2u * l] = p0;
            pSrc[2u * l + 1u] = p1;
            i += n1;
            m--;
         } while( m > 0);                   // butterfly loop end 

      }                           // groups loop end 

      twidCoefModifier <<= 1u;
   }                             // stages loop end 

   n1 = n2;
   n2 = n2 >> 1;
   ia = 0;

   cosVal = pCoef[ia * 2];
   sinVal = pCoef[(ia * 2) + 1];
   ia = ia + twidCoefModifier;

   // loop for butterfly 
   for (i = 0; i < fftLen; i += n1)
   {
      l = i + n2;
      xt = pSrc[2 * i] - pSrc[2 * l];
      pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);

      yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
      pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);

      pSrc[2u * l] = xt;

      pSrc[2u * l + 1u] = yt;

      i += n1;
      l = i + n2;

      xt = pSrc[2 * i] - pSrc[2 * l];
      pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);

      yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
      pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);

      pSrc[2u * l] = xt;

      pSrc[2u * l + 1u] = yt;

   }                             // butterfly loop end 

}


void arm_radix2_butterfly_inverse_q31(
q31_t * pSrc,
uint32_t fftLen,
q31_t * pCoef,
uint16_t twidCoefModifier)
{

   unsigned i, j, k, l;
   unsigned n1, n2, ia;
   q31_t xt, yt, cosVal, sinVal;
   q31_t p0, p1;

   //N = fftLen; 
   n2 = fftLen;

   n1 = n2;
   n2 = n2 >> 1;
   ia = 0;

   // loop for groups 
   for (i = 0; i < n2; i++)
   {
      cosVal = pCoef[ia * 2];
      sinVal = pCoef[(ia * 2) + 1];
      ia = ia + twidCoefModifier;

      l = i + n2;
      xt = (pSrc[2 * i] >> 1u) - (pSrc[2 * l] >> 1u);
      pSrc[2 * i] = ((pSrc[2 * i] >> 1u) + (pSrc[2 * l] >> 1u)) >> 1u;
      
      yt = (pSrc[2 * i + 1] >> 1u) - (pSrc[2 * l + 1] >> 1u);
      pSrc[2 * i + 1] =
        ((pSrc[2 * l + 1] >> 1u) + (pSrc[2 * i + 1] >> 1u)) >> 1u;

      mult_32x32_keep32_R(p0, xt, cosVal);
      mult_32x32_keep32_R(p1, yt, cosVal);
      multSub_32x32_keep32_R(p0, yt, sinVal);
      multAcc_32x32_keep32_R(p1, xt, sinVal);
      
      pSrc[2u * l] = p0;
      pSrc[2u * l + 1u] = p1;
   }                             // groups loop end 

   twidCoefModifier = twidCoefModifier << 1u;

   // loop for stage 
   for (k = fftLen / 2; k > 2; k = k >> 1)
   {
      n1 = n2;
      n2 = n2 >> 1;
      ia = 0;

      // loop for groups 
      for (j = 0; j < n2; j++)
      {
         cosVal = pCoef[ia * 2];
         sinVal = pCoef[(ia * 2) + 1];
         ia = ia + twidCoefModifier;

         // loop for butterfly 
         for (i = j; i < fftLen; i += n1)
         {
            l = i + n2;
            xt = pSrc[2 * i] - pSrc[2 * l];
            pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]) >> 1u;
      
            yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
            pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]) >> 1u;

            mult_32x32_keep32_R(p0, xt, cosVal);
            mult_32x32_keep32_R(p1, yt, cosVal);
            multSub_32x32_keep32_R(p0, yt, sinVal);
            multAcc_32x32_keep32_R(p1, xt, sinVal);
            
            pSrc[2u * l] = p0;
            pSrc[2u * l + 1u] = p1;
         }                         // butterfly loop end 

      }                           // groups loop end 

      twidCoefModifier = twidCoefModifier << 1u;
   }                             // stages loop end 

   n1 = n2;
   n2 = n2 >> 1;
   ia = 0;

   cosVal = pCoef[ia * 2];
   sinVal = pCoef[(ia * 2) + 1];
   ia = ia + twidCoefModifier;

   // loop for butterfly 
   for (i = 0; i < fftLen; i += n1)
   {
      l = i + n2;
      xt = pSrc[2 * i] - pSrc[2 * l];
      pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);

      yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
      pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);

      pSrc[2u * l] = xt;

      pSrc[2u * l + 1u] = yt;

      i += n1;
      l = i + n2;

      xt = pSrc[2 * i] - pSrc[2 * l];
      pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);

      yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
      pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);

      pSrc[2u * l] = xt;

      pSrc[2u * l + 1u] = yt;

   }                             // butterfly loop end 

}