Diff: cmsis_dsp/TransformFunctions/arm_cfft_f32.c

Revision:

3:7a284390b0ce

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/TransformFunctions/arm_cfft_f32.c	Fri Nov 08 13:45:10 2013 +0000
@@ -0,0 +1,616 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010-2013 ARM Limited. All rights reserved.    
+*    
+* $Date:        17. January 2013  
+* $Revision: 	V1.4.1  
+*    
+* Project: 	    CMSIS DSP Library    
+* Title:	    arm_cfft_f32.c   
+*    
+* Description:	Combined Radix Decimation in Frequency CFFT Floating 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"
+#include "arm_common_tables.h"
+
+extern void arm_radix8_butterfly_f32(
+  float32_t * pSrc,
+  uint16_t fftLen,
+  const float32_t * pCoef,
+  uint16_t twidCoefModifier);
+
+extern void arm_bitreversal_32(
+		uint32_t * pSrc,
+		const uint16_t bitRevLen,
+		const uint16_t * pBitRevTable);
+
+/**   
+* @ingroup groupTransforms   
+*/
+
+/**   
+* @defgroup ComplexFFT Complex FFT Functions   
+*   
+* \par
+* The Fast Fourier Transform (FFT) is an efficient algorithm for computing the
+* Discrete Fourier Transform (DFT).  The FFT can be orders of magnitude faster
+* than the DFT, especially for long lengths.
+* The algorithms described in this section
+* operate on complex data.  A separate set of functions is devoted to handling
+* of real sequences.
+* \par
+* There are separate algorithms for handling floating-point, Q15, and Q31 data
+* types.  The algorithms available for each data type are described next.
+* \par
+* The FFT functions operate in-place.  That is, the array holding the input data
+* will also be used to hold the corresponding result.  The input data is complex
+* and contains <code>2*fftLen</code> interleaved values as shown below.
+* <pre> {real[0], imag[0], real[1], imag[1],..} </pre>
+* The FFT result will be contained in the same array and the frequency domain
+* values will have the same interleaving.
+*
+* \par Floating-point
+* The floating-point complex FFT uses a mixed-radix algorithm.  Multiple radix-8
+* stages are performed along with a single radix-2 or radix-4 stage, as needed.
+* The algorithm supports lengths of [16, 32, 64, ..., 4096] and each length uses
+* a different twiddle factor table.  
+* \par
+* The function uses the standard FFT definition and output values may grow by a
+* factor of <code>fftLen</code> when computing the forward transform.  The
+* inverse transform includes a scale of <code>1/fftLen</code> as part of the
+* calculation and this matches the textbook definition of the inverse FFT.
+* \par
+* Preinitialized data structures containing twiddle factors and bit reversal
+* tables are provided and defined in <code>arm_const_structs.h</code>.  Include 
+* this header in your function and then pass one of the constant structures as 
+* an argument to arm_cfft_f32.  For example:
+* \par
+* <code>arm_cfft_f32(arm_cfft_sR_f32_len64, pSrc, 1, 1)</code>
+* \par
+* computes a 64-point inverse complex FFT including bit reversal.
+* The data structures are treated as constant data and not modified during the
+* calculation.  The same data structure can be reused for multiple transforms
+* including mixing forward and inverse transforms.
+* \par
+* Earlier releases of the library provided separate radix-2 and radix-4
+* algorithms that operated on floating-point data.  These functions are still
+* provided but are deprecated.  The older functions are slower and less general
+* than the new functions.
+* \par
+* An example of initialization of the constants for the arm_cfft_f32 function follows:
+* \par
+* const static arm_cfft_instance_f32 *S;
+* ...
+*		switch (length) {
+*    		case 16:
+*    			S = & arm_cfft_sR_f32_len16;
+*    		break;
+*    		case 32:
+*    			S = & arm_cfft_sR_f32_len32;
+*    		break;
+*			case 64:
+*    			S = & arm_cfft_sR_f32_len64;
+*    		break;
+*    		case 128:
+*    			S = & arm_cfft_sR_f32_len128;
+*    		break;
+*    		case 256:
+*    			S = & arm_cfft_sR_f32_len256;
+*    		break;
+*    		case 512:
+*    			S = & arm_cfft_sR_f32_len512;
+*    		break;
+*    		case 1024:
+*    			S = & arm_cfft_sR_f32_len1024;
+*    		break;
+*    		case 2048:
+*    			S = & arm_cfft_sR_f32_len2048;
+*    		break;
+*    		case 4096:
+*    			S = & arm_cfft_sR_f32_len4096;
+*    		break;
+*			}
+* \par Q15 and Q31
+* The library provides radix-2 and radix-4 FFT algorithms for fixed-point data.  The
+* radix-2 algorithm supports lengths of [16, 32, 64, ..., 4096].  The radix-4
+* algorithm supports lengths of [16, 64, 256, ..., 4096].  When possible, you
+* should use the radix-4 algorithm since it is faster than the radix-2 of the
+* same length.
+* \par
+* The forward FFTs include scaling in order to prevent results from overflowing.
+* Intermediate results are scaled down during each butterfly stage.  In the
+* radix-2 algorithm, a scale of 0.5 is applied during each butterfly.  In the
+* radix-4 algorithm, a scale of 0.25 is applied.  The scaling applies to both
+* the forward and the inverse FFTs.  Thus the forward FFT contains an additional
+* scale factor of <code>1/fftLen</code> as compared to the standard textbook
+* definition of the FFT.  The inverse FFT also scales down during each butterfly
+* stage and this corresponds to the standard textbook definition.
+* \par
+* A separate instance structure must be defined for each transform used but
+* twiddle factor and bit reversal tables can be reused.
+* \par 
+* There is also an associated initialization function for each data type.   
+* The initialization function performs the following operations:   
+* - Sets the values of the internal structure fields.   
+* - Initializes twiddle factor table and bit reversal table pointers.
+* \par   
+* Use of the initialization function is optional.   
+* However, if the initialization function is used, then the instance structure 
+* cannot be placed into a const data section. To place an instance structure 
+* into a const data section, the instance structure should be manually 
+* initialized as follows:
+* <pre>   
+*arm_cfft_radix2_instance_q31 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};   
+*arm_cfft_radix2_instance_q15 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};   
+*arm_cfft_radix4_instance_q31 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};    
+*arm_cfft_radix4_instance_q15 S = {fftLen, ifftFlag, bitReverseFlag, pTwiddle, pBitRevTable, twidCoefModifier, bitRevFactor};    
+*arm_cfft_instance_f32 S = {fftLen, pTwiddle, pBitRevTable, bitRevLength};
+* </pre>   
+* \par   
+* where <code>fftLen</code> length of CFFT/CIFFT; <code>ifftFlag</code> Flag for
+* selection of forward or inverse transform.  When ifftFlag is set the inverse
+* transform is calculated.
+* <code>bitReverseFlag</code> Flag for selection of output order (Set bitReverseFlag to output in normal order otherwise output in bit reversed order);    
+* <code>pTwiddle</code>points to array of twiddle coefficients; <code>pBitRevTable</code> points to the bit reversal table.   
+* <code>twidCoefModifier</code> modifier for twiddle factor table which supports all FFT lengths with same table;    
+* <code>pBitRevTable</code> modifier for bit reversal table which supports all FFT lengths with same table.   
+* <code>onebyfftLen</code> value of 1/fftLen to calculate CIFFT;
+* \par
+* The Q15 and Q31 FFT functions use a large bit reversal and twiddle factor
+* table.  The tables are defined for the maximum length transform and a subset
+* of the coefficients are used in shorter transforms.
+* 
+*/
+
+void arm_cfft_radix8by2_f32( arm_cfft_instance_f32 * S, float32_t * p1) 
+{
+   uint32_t    L  = S->fftLen;
+   float32_t * pCol1, * pCol2, * pMid1, * pMid2;
+   float32_t * p2 = p1 + L;
+   const float32_t * tw = (float32_t *) S->pTwiddle;
+   float32_t t1[4], t2[4], t3[4], t4[4], twR, twI;
+   float32_t m0, m1, m2, m3;
+   uint32_t l;
+
+   pCol1 = p1;
+   pCol2 = p2;
+
+   //    Define new length
+   L >>= 1;
+   //    Initialize mid pointers
+   pMid1 = p1 + L;
+   pMid2 = p2 + L;
+
+   // do two dot Fourier transform
+   for ( l = L >> 2; l > 0; l-- ) 
+   {
+      t1[0] = p1[0];
+      t1[1] = p1[1];
+      t1[2] = p1[2];
+      t1[3] = p1[3];
+
+      t2[0] = p2[0];
+      t2[1] = p2[1];
+      t2[2] = p2[2];
+      t2[3] = p2[3];
+
+      t3[0] = pMid1[0];
+      t3[1] = pMid1[1];
+      t3[2] = pMid1[2];
+      t3[3] = pMid1[3];
+
+      t4[0] = pMid2[0];
+      t4[1] = pMid2[1];
+      t4[2] = pMid2[2];
+      t4[3] = pMid2[3];
+
+      *p1++ = t1[0] + t2[0];
+      *p1++ = t1[1] + t2[1];
+      *p1++ = t1[2] + t2[2];
+      *p1++ = t1[3] + t2[3];    // col 1
+
+      t2[0] = t1[0] - t2[0];
+      t2[1] = t1[1] - t2[1];
+      t2[2] = t1[2] - t2[2];
+      t2[3] = t1[3] - t2[3];    // for col 2
+
+      *pMid1++ = t3[0] + t4[0];
+      *pMid1++ = t3[1] + t4[1];
+      *pMid1++ = t3[2] + t4[2];
+      *pMid1++ = t3[3] + t4[3]; // col 1
+
+      t4[0] = t4[0] - t3[0];
+      t4[1] = t4[1] - t3[1];
+      t4[2] = t4[2] - t3[2];
+      t4[3] = t4[3] - t3[3];    // for col 2
+
+      twR = *tw++;
+      twI = *tw++;
+
+      // multiply by twiddle factors
+      m0 = t2[0] * twR;
+      m1 = t2[1] * twI;
+      m2 = t2[1] * twR;
+      m3 = t2[0] * twI;
+      
+      // R  =  R  *  Tr - I * Ti
+      *p2++ = m0 + m1;
+      // I  =  I  *  Tr + R * Ti
+      *p2++ = m2 - m3;
+      
+      // use vertical symmetry
+	  //  0.9988 - 0.0491i <==> -0.0491 - 0.9988i
+      m0 = t4[0] * twI;
+      m1 = t4[1] * twR;
+      m2 = t4[1] * twI;
+      m3 = t4[0] * twR;
+      
+      *pMid2++ = m0 - m1;
+      *pMid2++ = m2 + m3;
+
+      twR = *tw++;
+      twI = *tw++;
+      
+      m0 = t2[2] * twR;
+      m1 = t2[3] * twI;
+      m2 = t2[3] * twR;
+      m3 = t2[2] * twI;
+      
+      *p2++ = m0 + m1;
+      *p2++ = m2 - m3;
+         
+      m0 = t4[2] * twI;
+      m1 = t4[3] * twR;
+      m2 = t4[3] * twI;
+      m3 = t4[2] * twR;
+      
+      *pMid2++ = m0 - m1;
+      *pMid2++ = m2 + m3;
+   }
+
+   // first col
+   arm_radix8_butterfly_f32( pCol1, L, (float32_t *) S->pTwiddle, 2u);
+   // second col
+   arm_radix8_butterfly_f32( pCol2, L, (float32_t *) S->pTwiddle, 2u);
+   
+}
+
+void arm_cfft_radix8by4_f32( arm_cfft_instance_f32 * S, float32_t * p1) 
+{
+   uint32_t    L  = S->fftLen >> 1;
+   float32_t * pCol1, *pCol2, *pCol3, *pCol4, *pEnd1, *pEnd2, *pEnd3, *pEnd4;
+	const float32_t *tw2, *tw3, *tw4;
+   float32_t * p2 = p1 + L;
+   float32_t * p3 = p2 + L;
+   float32_t * p4 = p3 + L;
+   float32_t t2[4], t3[4], t4[4], twR, twI;
+   float32_t p1ap3_0, p1sp3_0, p1ap3_1, p1sp3_1;
+   float32_t m0, m1, m2, m3;
+   uint32_t l, twMod2, twMod3, twMod4;
+
+   pCol1 = p1;         // points to real values by default
+   pCol2 = p2;
+   pCol3 = p3;
+   pCol4 = p4;
+   pEnd1 = p2 - 1;     // points to imaginary values by default
+   pEnd2 = p3 - 1;
+   pEnd3 = p4 - 1;
+   pEnd4 = pEnd3 + L;
+   
+   tw2 = tw3 = tw4 = (float32_t *) S->pTwiddle;
+   
+   L >>= 1;
+
+   // do four dot Fourier transform
+
+   twMod2 = 2;
+   twMod3 = 4;
+   twMod4 = 6;
+
+   // TOP
+   p1ap3_0 = p1[0] + p3[0];
+   p1sp3_0 = p1[0] - p3[0];
+   p1ap3_1 = p1[1] + p3[1];
+   p1sp3_1 = p1[1] - p3[1];
+
+   // col 2
+   t2[0] = p1sp3_0 + p2[1] - p4[1];
+   t2[1] = p1sp3_1 - p2[0] + p4[0];
+   // col 3
+   t3[0] = p1ap3_0 - p2[0] - p4[0];
+   t3[1] = p1ap3_1 - p2[1] - p4[1];
+   // col 4
+   t4[0] = p1sp3_0 - p2[1] + p4[1];
+   t4[1] = p1sp3_1 + p2[0] - p4[0];
+   // col 1
+   *p1++ = p1ap3_0 + p2[0] + p4[0];
+   *p1++ = p1ap3_1 + p2[1] + p4[1];
+
+   // Twiddle factors are ones
+   *p2++ = t2[0];
+   *p2++ = t2[1];
+   *p3++ = t3[0];
+   *p3++ = t3[1];
+   *p4++ = t4[0];
+   *p4++ = t4[1];
+   
+   tw2 += twMod2;
+   tw3 += twMod3;
+   tw4 += twMod4;
+   
+   for (l = (L - 2) >> 1; l > 0; l-- ) 
+   {
+
+      // TOP
+      p1ap3_0 = p1[0] + p3[0];
+      p1sp3_0 = p1[0] - p3[0];
+      p1ap3_1 = p1[1] + p3[1];
+      p1sp3_1 = p1[1] - p3[1];
+      // col 2
+      t2[0] = p1sp3_0 + p2[1] - p4[1];
+      t2[1] = p1sp3_1 - p2[0] + p4[0];
+      // col 3
+      t3[0] = p1ap3_0 - p2[0] - p4[0];
+      t3[1] = p1ap3_1 - p2[1] - p4[1];
+      // col 4
+      t4[0] = p1sp3_0 - p2[1] + p4[1];
+      t4[1] = p1sp3_1 + p2[0] - p4[0];
+      // col 1 - top
+      *p1++ = p1ap3_0 + p2[0] + p4[0];
+      *p1++ = p1ap3_1 + p2[1] + p4[1];
+
+      // BOTTOM
+      p1ap3_1 = pEnd1[-1] + pEnd3[-1];
+      p1sp3_1 = pEnd1[-1] - pEnd3[-1];
+      p1ap3_0 = pEnd1[0] + pEnd3[0];
+      p1sp3_0 = pEnd1[0] - pEnd3[0];
+      // col 2
+      t2[2] = pEnd2[0]  - pEnd4[0] + p1sp3_1;
+      t2[3] = pEnd1[0] - pEnd3[0] - pEnd2[-1] + pEnd4[-1];
+      // col 3
+      t3[2] = p1ap3_1 - pEnd2[-1] - pEnd4[-1];
+      t3[3] = p1ap3_0 - pEnd2[0]  - pEnd4[0];
+      // col 4
+      t4[2] = pEnd2[0]  - pEnd4[0]  - p1sp3_1;
+      t4[3] = pEnd4[-1] - pEnd2[-1] - p1sp3_0;
+      // col 1 - Bottom
+      *pEnd1-- = p1ap3_0 + pEnd2[0] + pEnd4[0];
+      *pEnd1-- = p1ap3_1 + pEnd2[-1] + pEnd4[-1];
+
+      // COL 2
+      // read twiddle factors
+      twR = *tw2++;
+      twI = *tw2++;
+      // multiply by twiddle factors
+      //  let    Z1 = a + i(b),   Z2 = c + i(d)
+      //   =>  Z1 * Z2  =  (a*c - b*d) + i(b*c + a*d)
+      // Top
+      m0 = t2[0] * twR;
+      m1 = t2[1] * twI;
+      m2 = t2[1] * twR;
+      m3 = t2[0] * twI;
+      
+      *p2++ = m0 + m1;
+      *p2++ = m2 - m3;
+      // use vertical symmetry col 2
+      // 0.9997 - 0.0245i  <==>  0.0245 - 0.9997i
+      // Bottom
+      m0 = t2[3] * twI;
+      m1 = t2[2] * twR;
+      m2 = t2[2] * twI;
+      m3 = t2[3] * twR;
+      
+      *pEnd2-- = m0 - m1;
+      *pEnd2-- = m2 + m3;
+
+      // COL 3
+      twR = tw3[0];
+      twI = tw3[1];
+      tw3 += twMod3;
+      // Top
+      m0 = t3[0] * twR;
+      m1 = t3[1] * twI;
+      m2 = t3[1] * twR;
+      m3 = t3[0] * twI;
+      
+      *p3++ = m0 + m1;
+      *p3++ = m2 - m3;
+      // use vertical symmetry col 3
+      // 0.9988 - 0.0491i  <==>  -0.9988 - 0.0491i
+      // Bottom
+      m0 = -t3[3] * twR;
+      m1 = t3[2] * twI;
+      m2 = t3[2] * twR;
+      m3 = t3[3] * twI;
+      
+      *pEnd3-- = m0 - m1;
+      *pEnd3-- = m3 - m2;
+      
+      // COL 4
+      twR = tw4[0];
+      twI = tw4[1];
+      tw4 += twMod4;
+      // Top
+      m0 = t4[0] * twR;
+      m1 = t4[1] * twI;
+      m2 = t4[1] * twR;
+      m3 = t4[0] * twI;
+      
+      *p4++ = m0 + m1;
+      *p4++ = m2 - m3;
+      // use vertical symmetry col 4
+      // 0.9973 - 0.0736i  <==>  -0.0736 + 0.9973i
+      // Bottom
+      m0 = t4[3] * twI;
+      m1 = t4[2] * twR;
+      m2 = t4[2] * twI;
+      m3 = t4[3] * twR;
+      
+      *pEnd4-- = m0 - m1;
+      *pEnd4-- = m2 + m3;
+   }
+
+   //MIDDLE
+   // Twiddle factors are 
+   //  1.0000  0.7071-0.7071i  -1.0000i  -0.7071-0.7071i
+   p1ap3_0 = p1[0] + p3[0];
+   p1sp3_0 = p1[0] - p3[0];
+   p1ap3_1 = p1[1] + p3[1];
+   p1sp3_1 = p1[1] - p3[1];
+
+   // col 2
+   t2[0] = p1sp3_0 + p2[1] - p4[1];
+   t2[1] = p1sp3_1 - p2[0] + p4[0];
+   // col 3
+   t3[0] = p1ap3_0 - p2[0] - p4[0];
+   t3[1] = p1ap3_1 - p2[1] - p4[1];
+   // col 4
+   t4[0] = p1sp3_0 - p2[1] + p4[1];
+   t4[1] = p1sp3_1 + p2[0] - p4[0];
+   // col 1 - Top
+   *p1++ = p1ap3_0 + p2[0] + p4[0];
+   *p1++ = p1ap3_1 + p2[1] + p4[1];
+   
+   // COL 2
+   twR = tw2[0];
+   twI = tw2[1];
+   
+   m0 = t2[0] * twR;
+   m1 = t2[1] * twI;
+   m2 = t2[1] * twR;
+   m3 = t2[0] * twI;
+   
+   *p2++ = m0 + m1;
+   *p2++ = m2 - m3;
+      // COL 3
+   twR = tw3[0];
+   twI = tw3[1];
+   
+   m0 = t3[0] * twR;
+   m1 = t3[1] * twI;
+   m2 = t3[1] * twR;
+   m3 = t3[0] * twI;
+   
+   *p3++ = m0 + m1;
+   *p3++ = m2 - m3;
+   // COL 4
+   twR = tw4[0];
+   twI = tw4[1];
+   
+   m0 = t4[0] * twR;
+   m1 = t4[1] * twI;
+   m2 = t4[1] * twR;
+   m3 = t4[0] * twI;
+   
+   *p4++ = m0 + m1;
+   *p4++ = m2 - m3;
+
+   // first col
+   arm_radix8_butterfly_f32( pCol1, L, (float32_t *) S->pTwiddle, 4u);
+   // second col
+   arm_radix8_butterfly_f32( pCol2, L, (float32_t *) S->pTwiddle, 4u);
+   // third col
+   arm_radix8_butterfly_f32( pCol3, L, (float32_t *) S->pTwiddle, 4u);
+   // fourth col
+   arm_radix8_butterfly_f32( pCol4, L, (float32_t *) S->pTwiddle, 4u);
+
+}
+
+/**
+* @addtogroup ComplexFFT   
+* @{   
+*/
+
+/**   
+* @details   
+* @brief       Processing function for the floating-point complex FFT.
+* @param[in]      *S    points to an instance of the floating-point CFFT structure.  
+* @param[in, out] *p1   points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.  
+* @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 none.  
+*/
+
+void arm_cfft_f32( 
+   const arm_cfft_instance_f32 * S, 
+   float32_t * p1,
+   uint8_t ifftFlag,
+   uint8_t bitReverseFlag)
+{
+
+   uint32_t  L = S->fftLen, l;
+   float32_t invL, * pSrc;
+
+  if(ifftFlag == 1u)
+  {
+	  /*  Conjugate input data  */
+	  pSrc = p1 + 1;
+	  for(l=0; l<L; l++) {
+		  *pSrc = -*pSrc;
+		   pSrc += 2;
+	  }
+  }
+
+		switch (L) {
+		case 16: 
+		case 128:
+		case 1024:
+			 arm_cfft_radix8by2_f32  ( (arm_cfft_instance_f32 *) S, p1);
+			 break;
+		case 32:
+		case 256:
+		case 2048:
+			 arm_cfft_radix8by4_f32  ( (arm_cfft_instance_f32 *) S, p1);
+			 break;
+		case 64:
+		case 512:
+		case 4096:
+          arm_radix8_butterfly_f32( p1, L, (float32_t *) S->pTwiddle, 1);
+			 break;
+		}  
+
+	if( bitReverseFlag )
+		arm_bitreversal_32((uint32_t*)p1,S->bitRevLength,S->pBitRevTable);
+
+  if(ifftFlag == 1u)
+  {
+	  invL = 1.0f/(float32_t)L;
+	  /*  Conjugate and scale output data */
+	  pSrc = p1;
+	  for(l=0; l<L; l++) {
+  		 *pSrc++ *=   invL ;
+		 *pSrc  = -(*pSrc) * invL;
+                 pSrc++;
+	  }
+  }
+}
+