Diff: TransformFunctions/arm_cfft_radix2_q15.c

Revision:

0:3d9c67d97d6f

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TransformFunctions/arm_cfft_radix2_q15.c	Mon Jul 28 15:03:15 2014 +0000
@@ -0,0 +1,741 @@
+/* ----------------------------------------------------------------------   
+* Copyright (C) 2010-2014 ARM Limited. All rights reserved.   
+*   
+* $Date:        12. March 2014  
+* $Revision: 	V1.4.3  
+*   
+* Project: 	    CMSIS DSP Library   
+* Title:	    arm_cfft_radix2_q15.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
+* 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
+* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+* POSSIBILITY OF SUCH DAMAGE.   
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+void arm_radix2_butterfly_q15(
+  q15_t * pSrc,
+  uint32_t fftLen,
+  q15_t * pCoef,
+  uint16_t twidCoefModifier);
+
+void arm_radix2_butterfly_inverse_q15(
+  q15_t * pSrc,
+  uint32_t fftLen,
+  q15_t * pCoef,
+  uint16_t twidCoefModifier);
+	
+void arm_bitreversal_q15(
+  q15_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.  
+ * @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_q15(
+  const arm_cfft_radix2_instance_q15 * S,
+  q15_t * pSrc)
+{
+
+  if(S->ifftFlag == 1u)
+  {
+    arm_radix2_butterfly_inverse_q15(pSrc, S->fftLen,
+                                     S->pTwiddle, S->twidCoefModifier);
+  }
+  else
+  {
+    arm_radix2_butterfly_q15(pSrc, S->fftLen,
+                             S->pTwiddle, S->twidCoefModifier);
+  }
+
+  arm_bitreversal_q15(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
+}
+
+/**   
+ * @} end of ComplexFFT group   
+ */
+
+void arm_radix2_butterfly_q15(
+  q15_t * pSrc,
+  uint32_t fftLen,
+  q15_t * pCoef,
+  uint16_t twidCoefModifier)
+{
+#ifndef ARM_MATH_CM0_FAMILY
+
+  unsigned i, j, k, l;
+  unsigned n1, n2, ia;
+  q15_t in;
+  q31_t T, S, R;
+  q31_t coeff, out1, out2;
+
+  //N = fftLen; 
+  n2 = fftLen;
+
+  n1 = n2;
+  n2 = n2 >> 1;
+  ia = 0;
+
+  // loop for groups 
+  for (i = 0; i < n2; i++)
+  {
+    coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+    ia = ia + twidCoefModifier;
+
+    l = i + n2;
+
+    T = _SIMD32_OFFSET(pSrc + (2 * i));
+    in = ((int16_t) (T & 0xFFFF)) >> 1;
+    T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    S = _SIMD32_OFFSET(pSrc + (2 * l));
+    in = ((int16_t) (S & 0xFFFF)) >> 1;
+    S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    R = __QSUB16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+    out1 = __SMUAD(coeff, R) >> 16;
+    out2 = __SMUSDX(coeff, R);
+
+#else
+
+    out1 = __SMUSDX(R, coeff) >> 16u;
+    out2 = __SMUAD(coeff, R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+    _SIMD32_OFFSET(pSrc + (2u * l)) =
+      (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+    coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+    ia = ia + twidCoefModifier;
+
+    // loop for butterfly 
+    i++;
+    l++;
+
+    T = _SIMD32_OFFSET(pSrc + (2 * i));
+    in = ((int16_t) (T & 0xFFFF)) >> 1;
+    T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    S = _SIMD32_OFFSET(pSrc + (2 * l));
+    in = ((int16_t) (S & 0xFFFF)) >> 1;
+    S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    R = __QSUB16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+    out1 = __SMUAD(coeff, R) >> 16;
+    out2 = __SMUSDX(coeff, R);
+
+#else
+
+    out1 = __SMUSDX(R, coeff) >> 16u;
+    out2 = __SMUAD(coeff, R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+    _SIMD32_OFFSET(pSrc + (2u * l)) =
+      (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+  }                             // 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++)
+    {
+      coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+      ia = ia + twidCoefModifier;
+
+      // loop for butterfly 
+      for (i = j; i < fftLen; i += n1)
+      {
+        l = i + n2;
+
+        T = _SIMD32_OFFSET(pSrc + (2 * i));
+
+        S = _SIMD32_OFFSET(pSrc + (2 * l));
+
+        R = __QSUB16(T, S);
+
+        _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+        out1 = __SMUAD(coeff, R) >> 16;
+        out2 = __SMUSDX(coeff, R);
+
+#else
+
+        out1 = __SMUSDX(R, coeff) >> 16u;
+        out2 = __SMUAD(coeff, R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+        _SIMD32_OFFSET(pSrc + (2u * l)) =
+          (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+        i += n1;
+
+        l = i + n2;
+
+        T = _SIMD32_OFFSET(pSrc + (2 * i));
+
+        S = _SIMD32_OFFSET(pSrc + (2 * l));
+
+        R = __QSUB16(T, S);
+
+        _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+        out1 = __SMUAD(coeff, R) >> 16;
+        out2 = __SMUSDX(coeff, R);
+
+#else
+
+        out1 = __SMUSDX(R, coeff) >> 16u;
+        out2 = __SMUAD(coeff, R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+        _SIMD32_OFFSET(pSrc + (2u * l)) =
+          (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+      }                         // butterfly loop end 
+
+    }                           // groups loop end 
+
+    twidCoefModifier = twidCoefModifier << 1u;
+  }                             // stages loop end 
+
+  n1 = n2;
+  n2 = n2 >> 1;
+  ia = 0;
+
+  coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+  ia = ia + twidCoefModifier;
+
+  // loop for butterfly 
+  for (i = 0; i < fftLen; i += n1)
+  {
+    l = i + n2;
+
+    T = _SIMD32_OFFSET(pSrc + (2 * i));
+
+    S = _SIMD32_OFFSET(pSrc + (2 * l));
+
+    R = __QSUB16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2 * i)) = __QADD16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2u * l)) = R;
+
+    i += n1;
+    l = i + n2;
+
+    T = _SIMD32_OFFSET(pSrc + (2 * i));
+
+    S = _SIMD32_OFFSET(pSrc + (2 * l));
+
+    R = __QSUB16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2 * i)) = __QADD16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2u * l)) = R;
+
+  }                             // groups loop end 
+
+
+#else
+
+  unsigned i, j, k, l;
+  unsigned n1, n2, ia;
+  q15_t xt, yt, cosVal, sinVal;
+
+
+  //N = fftLen; 
+  n2 = fftLen;
+
+  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] >> 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;
+
+      pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) +
+                      ((int16_t) (((q31_t) yt * sinVal) >> 16)));
+
+      pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) -
+                           ((int16_t) (((q31_t) xt * sinVal) >> 16)));
+
+    }                           // butterfly loop end 
+
+  }                             // 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;
+
+        pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) +
+                        ((int16_t) (((q31_t) yt * sinVal) >> 16)));
+
+        pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) -
+                             ((int16_t) (((q31_t) xt * sinVal) >> 16)));
+
+      }                         // butterfly loop end 
+
+    }                           // groups loop end 
+
+    twidCoefModifier = twidCoefModifier << 1u;
+  }                             // stages loop end 
+
+  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]);
+
+      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 
+
+  }                             // groups loop end 
+
+  twidCoefModifier = twidCoefModifier << 1u;
+
+#endif //             #ifndef ARM_MATH_CM0_FAMILY
+
+}
+
+
+void arm_radix2_butterfly_inverse_q15(
+  q15_t * pSrc,
+  uint32_t fftLen,
+  q15_t * pCoef,
+  uint16_t twidCoefModifier)
+{
+#ifndef ARM_MATH_CM0_FAMILY
+
+  unsigned i, j, k, l;
+  unsigned n1, n2, ia;
+  q15_t in;
+  q31_t T, S, R;
+  q31_t coeff, out1, out2;
+
+  //N = fftLen; 
+  n2 = fftLen;
+
+  n1 = n2;
+  n2 = n2 >> 1;
+  ia = 0;
+
+  // loop for groups 
+  for (i = 0; i < n2; i++)
+  {
+    coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+    ia = ia + twidCoefModifier;
+
+    l = i + n2;
+
+    T = _SIMD32_OFFSET(pSrc + (2 * i));
+    in = ((int16_t) (T & 0xFFFF)) >> 1;
+    T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    S = _SIMD32_OFFSET(pSrc + (2 * l));
+    in = ((int16_t) (S & 0xFFFF)) >> 1;
+    S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    R = __QSUB16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+    out1 = __SMUSD(coeff, R) >> 16;
+    out2 = __SMUADX(coeff, R);
+#else
+
+    out1 = __SMUADX(R, coeff) >> 16u;
+    out2 = __SMUSD(__QSUB(0, coeff), R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+    _SIMD32_OFFSET(pSrc + (2u * l)) =
+      (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+    coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+    ia = ia + twidCoefModifier;
+
+    // loop for butterfly 
+    i++;
+    l++;
+
+    T = _SIMD32_OFFSET(pSrc + (2 * i));
+    in = ((int16_t) (T & 0xFFFF)) >> 1;
+    T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    S = _SIMD32_OFFSET(pSrc + (2 * l));
+    in = ((int16_t) (S & 0xFFFF)) >> 1;
+    S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+
+    R = __QSUB16(T, S);
+
+    _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+    out1 = __SMUSD(coeff, R) >> 16;
+    out2 = __SMUADX(coeff, R);
+#else
+
+    out1 = __SMUADX(R, coeff) >> 16u;
+    out2 = __SMUSD(__QSUB(0, coeff), R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+    _SIMD32_OFFSET(pSrc + (2u * l)) =
+      (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+  }                             // 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++)
+    {
+      coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+      ia = ia + twidCoefModifier;
+
+      // loop for butterfly 
+      for (i = j; i < fftLen; i += n1)
+      {
+        l = i + n2;
+
+        T = _SIMD32_OFFSET(pSrc + (2 * i));
+
+        S = _SIMD32_OFFSET(pSrc + (2 * l));
+
+        R = __QSUB16(T, S);
+
+        _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+        out1 = __SMUSD(coeff, R) >> 16;
+        out2 = __SMUADX(coeff, R);
+
+#else
+
+        out1 = __SMUADX(R, coeff) >> 16u;
+        out2 = __SMUSD(__QSUB(0, coeff), R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+        _SIMD32_OFFSET(pSrc + (2u * l)) =
+          (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+        i += n1;
+
+        l = i + n2;
+
+        T = _SIMD32_OFFSET(pSrc + (2 * i));
+
+        S = _SIMD32_OFFSET(pSrc + (2 * l));
+
+        R = __QSUB16(T, S);
+
+        _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+        out1 = __SMUSD(coeff, R) >> 16;
+        out2 = __SMUADX(coeff, R);
+#else
+
+        out1 = __SMUADX(R, coeff) >> 16u;
+        out2 = __SMUSD(__QSUB(0, coeff), R);
+
+#endif //     #ifndef ARM_MATH_BIG_ENDIAN
+
+        _SIMD32_OFFSET(pSrc + (2u * l)) =
+          (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+      }                         // butterfly loop end 
+
+    }                           // groups loop end 
+
+    twidCoefModifier = twidCoefModifier << 1u;
+  }                             // stages loop end 
+
+  n1 = n2;
+  n2 = n2 >> 1;
+  ia = 0;
+
+  // loop for groups 
+  for (j = 0; j < n2; j++)
+  {
+    coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
+
+    ia = ia + twidCoefModifier;
+
+    // loop for butterfly 
+    for (i = j; i < fftLen; i += n1)
+    {
+      l = i + n2;
+
+      T = _SIMD32_OFFSET(pSrc + (2 * i));
+
+      S = _SIMD32_OFFSET(pSrc + (2 * l));
+
+      R = __QSUB16(T, S);
+
+      _SIMD32_OFFSET(pSrc + (2 * i)) = __QADD16(T, S);
+
+      _SIMD32_OFFSET(pSrc + (2u * l)) = R;
+
+    }                           // butterfly loop end 
+
+  }                             // groups loop end 
+
+  twidCoefModifier = twidCoefModifier << 1u;
+
+#else
+
+
+  unsigned i, j, k, l;
+  unsigned n1, n2, ia;
+  q15_t xt, yt, cosVal, sinVal;
+
+  //N = fftLen; 
+  n2 = fftLen;
+
+  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] >> 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;
+
+      pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) -
+                      ((int16_t) (((q31_t) yt * sinVal) >> 16)));
+
+      pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) +
+                           ((int16_t) (((q31_t) xt * sinVal) >> 16)));
+
+    }                           // butterfly loop end 
+
+  }                             // 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;
+
+        pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) -
+                        ((int16_t) (((q31_t) yt * sinVal) >> 16)));
+
+        pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) +
+                             ((int16_t) (((q31_t) xt * sinVal) >> 16)));
+
+      }                         // 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;
+
+  }                             // groups loop end 
+
+
+#endif //             #ifndef ARM_MATH_CM0_FAMILY
+
+}