arm_cfft_f32.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        19. March 2015 
00005 * $Revision:    V.1.4.5  
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_cfft_f32.c   
00009 *    
00010 * Description:  Combined Radix Decimation in Frequency CFFT Floating point processing function
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.   
00039 * -------------------------------------------------------------------- */
00040 
00041 #include "arm_math.h"
00042 #include "arm_common_tables.h"
00043 
00044 extern void arm_radix8_butterfly_f32(
00045     float32_t * pSrc,
00046     uint16_t fftLen,
00047     const float32_t * pCoef,
00048     uint16_t twidCoefModifier);
00049 
00050 extern void arm_bitreversal_32(
00051     uint32_t * pSrc,
00052     const uint16_t bitRevLen,
00053     const uint16_t * pBitRevTable);
00054 
00055 /**   
00056 * @ingroup groupTransforms   
00057 */
00058 
00059 /**   
00060 * @defgroup ComplexFFT Complex FFT Functions   
00061 *   
00062 * \par
00063 * The Fast Fourier Transform (FFT) is an efficient algorithm for computing the
00064 * Discrete Fourier Transform (DFT).  The FFT can be orders of magnitude faster
00065 * than the DFT, especially for long lengths.
00066 * The algorithms described in this section
00067 * operate on complex data.  A separate set of functions is devoted to handling
00068 * of real sequences.
00069 * \par
00070 * There are separate algorithms for handling floating-point, Q15, and Q31 data
00071 * types.  The algorithms available for each data type are described next.
00072 * \par
00073 * The FFT functions operate in-place.  That is, the array holding the input data
00074 * will also be used to hold the corresponding result.  The input data is complex
00075 * and contains <code>2*fftLen</code> interleaved values as shown below.
00076 * <pre> {real[0], imag[0], real[1], imag[1],..} </pre>
00077 * The FFT result will be contained in the same array and the frequency domain
00078 * values will have the same interleaving.
00079 *
00080 * \par Floating-point
00081 * The floating-point complex FFT uses a mixed-radix algorithm.  Multiple radix-8
00082 * stages are performed along with a single radix-2 or radix-4 stage, as needed.
00083 * The algorithm supports lengths of [16, 32, 64, ..., 4096] and each length uses
00084 * a different twiddle factor table.  
00085 * \par
00086 * The function uses the standard FFT definition and output values may grow by a
00087 * factor of <code>fftLen</code> when computing the forward transform.  The
00088 * inverse transform includes a scale of <code>1/fftLen</code> as part of the
00089 * calculation and this matches the textbook definition of the inverse FFT.
00090 * \par
00091 * Pre-initialized data structures containing twiddle factors and bit reversal
00092 * tables are provided and defined in <code>arm_const_structs.h</code>.  Include 
00093 * this header in your function and then pass one of the constant structures as 
00094 * an argument to arm_cfft_f32.  For example:
00095 * \par
00096 * <code>arm_cfft_f32(arm_cfft_sR_f32_len64, pSrc, 1, 1)</code>
00097 * \par
00098 * computes a 64-point inverse complex FFT including bit reversal.
00099 * The data structures are treated as constant data and not modified during the
00100 * calculation.  The same data structure can be reused for multiple transforms
00101 * including mixing forward and inverse transforms.
00102 * \par
00103 * Earlier releases of the library provided separate radix-2 and radix-4
00104 * algorithms that operated on floating-point data.  These functions are still
00105 * provided but are deprecated.  The older functions are slower and less general
00106 * than the new functions.
00107 * \par
00108 * An example of initialization of the constants for the arm_cfft_f32 function follows:
00109 * \code
00110 * const static arm_cfft_instance_f32 *S;
00111 * ...
00112 *   switch (length) {
00113 *     case 16:
00114 *       S = &arm_cfft_sR_f32_len16;
00115 *       break;
00116 *     case 32:
00117 *       S = &arm_cfft_sR_f32_len32;
00118 *       break;
00119 *     case 64:
00120 *       S = &arm_cfft_sR_f32_len64;
00121 *       break;
00122 *     case 128:
00123 *       S = &arm_cfft_sR_f32_len128;
00124 *       break;
00125 *     case 256:
00126 *       S = &arm_cfft_sR_f32_len256;
00127 *       break;
00128 *     case 512:
00129 *       S = &arm_cfft_sR_f32_len512;
00130 *       break;
00131 *     case 1024:
00132 *       S = &arm_cfft_sR_f32_len1024;
00133 *       break;
00134 *     case 2048:
00135 *       S = &arm_cfft_sR_f32_len2048;
00136 *       break;
00137 *     case 4096:
00138 *       S = &arm_cfft_sR_f32_len4096;
00139 *       break;
00140 *   }
00141 * \endcode
00142 * \par Q15 and Q31
00143 * The floating-point complex FFT uses a mixed-radix algorithm.  Multiple radix-4
00144 * stages are performed along with a single radix-2 stage, as needed.
00145 * The algorithm supports lengths of [16, 32, 64, ..., 4096] and each length uses
00146 * a different twiddle factor table.  
00147 * \par
00148 * The function uses the standard FFT definition and output values may grow by a
00149 * factor of <code>fftLen</code> when computing the forward transform.  The
00150 * inverse transform includes a scale of <code>1/fftLen</code> as part of the
00151 * calculation and this matches the textbook definition of the inverse FFT.
00152 * \par
00153 * Pre-initialized data structures containing twiddle factors and bit reversal
00154 * tables are provided and defined in <code>arm_const_structs.h</code>.  Include 
00155 * this header in your function and then pass one of the constant structures as 
00156 * an argument to arm_cfft_q31.  For example:
00157 * \par
00158 * <code>arm_cfft_q31(arm_cfft_sR_q31_len64, pSrc, 1, 1)</code>
00159 * \par
00160 * computes a 64-point inverse complex FFT including bit reversal.
00161 * The data structures are treated as constant data and not modified during the
00162 * calculation.  The same data structure can be reused for multiple transforms
00163 * including mixing forward and inverse transforms.
00164 * \par
00165 * Earlier releases of the library provided separate radix-2 and radix-4
00166 * algorithms that operated on floating-point data.  These functions are still
00167 * provided but are deprecated.  The older functions are slower and less general
00168 * than the new functions.
00169 * \par
00170 * An example of initialization of the constants for the arm_cfft_q31 function follows:
00171 * \code
00172 * const static arm_cfft_instance_q31 *S;
00173 * ...
00174 *   switch (length) {
00175 *     case 16:
00176 *       S = &arm_cfft_sR_q31_len16;
00177 *       break;
00178 *     case 32:
00179 *       S = &arm_cfft_sR_q31_len32;
00180 *       break;
00181 *     case 64:
00182 *       S = &arm_cfft_sR_q31_len64;
00183 *       break;
00184 *     case 128:
00185 *       S = &arm_cfft_sR_q31_len128;
00186 *       break;
00187 *     case 256:
00188 *       S = &arm_cfft_sR_q31_len256;
00189 *       break;
00190 *     case 512:
00191 *       S = &arm_cfft_sR_q31_len512;
00192 *       break;
00193 *     case 1024:
00194 *       S = &arm_cfft_sR_q31_len1024;
00195 *       break;
00196 *     case 2048:
00197 *       S = &arm_cfft_sR_q31_len2048;
00198 *       break;
00199 *     case 4096:
00200 *       S = &arm_cfft_sR_q31_len4096;
00201 *       break;
00202 *   }
00203 * \endcode
00204 * 
00205 */
00206 
00207 void arm_cfft_radix8by2_f32( arm_cfft_instance_f32 * S, float32_t * p1) 
00208 {
00209     uint32_t    L  = S->fftLen;
00210     float32_t * pCol1, * pCol2, * pMid1, * pMid2;
00211     float32_t * p2 = p1 + L;
00212     const float32_t * tw = (float32_t *) S->pTwiddle;
00213     float32_t t1[4], t2[4], t3[4], t4[4], twR, twI;
00214     float32_t m0, m1, m2, m3;
00215     uint32_t l;
00216 
00217     pCol1 = p1;
00218     pCol2 = p2;
00219 
00220     //    Define new length
00221     L >>= 1;
00222     //    Initialize mid pointers
00223     pMid1 = p1 + L;
00224     pMid2 = p2 + L;
00225 
00226     // do two dot Fourier transform
00227     for ( l = L >> 2; l > 0; l-- ) 
00228     {
00229         t1[0] = p1[0];
00230         t1[1] = p1[1];
00231         t1[2] = p1[2];
00232         t1[3] = p1[3];
00233 
00234         t2[0] = p2[0];
00235         t2[1] = p2[1];
00236         t2[2] = p2[2];
00237         t2[3] = p2[3];
00238 
00239         t3[0] = pMid1[0];
00240         t3[1] = pMid1[1];
00241         t3[2] = pMid1[2];
00242         t3[3] = pMid1[3];
00243 
00244         t4[0] = pMid2[0];
00245         t4[1] = pMid2[1];
00246         t4[2] = pMid2[2];
00247         t4[3] = pMid2[3];
00248 
00249         *p1++ = t1[0] + t2[0];
00250         *p1++ = t1[1] + t2[1];
00251         *p1++ = t1[2] + t2[2];
00252         *p1++ = t1[3] + t2[3];    // col 1
00253 
00254         t2[0] = t1[0] - t2[0];
00255         t2[1] = t1[1] - t2[1];
00256         t2[2] = t1[2] - t2[2];
00257         t2[3] = t1[3] - t2[3];    // for col 2
00258 
00259         *pMid1++ = t3[0] + t4[0];
00260         *pMid1++ = t3[1] + t4[1];
00261         *pMid1++ = t3[2] + t4[2];
00262         *pMid1++ = t3[3] + t4[3]; // col 1
00263 
00264         t4[0] = t4[0] - t3[0];
00265         t4[1] = t4[1] - t3[1];
00266         t4[2] = t4[2] - t3[2];
00267         t4[3] = t4[3] - t3[3];    // for col 2
00268 
00269         twR = *tw++;
00270         twI = *tw++;
00271 
00272         // multiply by twiddle factors
00273         m0 = t2[0] * twR;
00274         m1 = t2[1] * twI;
00275         m2 = t2[1] * twR;
00276         m3 = t2[0] * twI;
00277         
00278         // R  =  R  *  Tr - I * Ti
00279         *p2++ = m0 + m1;
00280         // I  =  I  *  Tr + R * Ti
00281         *p2++ = m2 - m3;
00282         
00283         // use vertical symmetry
00284         //  0.9988 - 0.0491i <==> -0.0491 - 0.9988i
00285         m0 = t4[0] * twI;
00286         m1 = t4[1] * twR;
00287         m2 = t4[1] * twI;
00288         m3 = t4[0] * twR;
00289         
00290         *pMid2++ = m0 - m1;
00291         *pMid2++ = m2 + m3;
00292 
00293         twR = *tw++;
00294         twI = *tw++;
00295         
00296         m0 = t2[2] * twR;
00297         m1 = t2[3] * twI;
00298         m2 = t2[3] * twR;
00299         m3 = t2[2] * twI;
00300         
00301         *p2++ = m0 + m1;
00302         *p2++ = m2 - m3;
00303         
00304         m0 = t4[2] * twI;
00305         m1 = t4[3] * twR;
00306         m2 = t4[3] * twI;
00307         m3 = t4[2] * twR;
00308         
00309         *pMid2++ = m0 - m1;
00310         *pMid2++ = m2 + m3;
00311     }
00312 
00313     // first col
00314     arm_radix8_butterfly_f32( pCol1, L, (float32_t *) S->pTwiddle, 2u);
00315     // second col
00316     arm_radix8_butterfly_f32( pCol2, L, (float32_t *) S->pTwiddle, 2u);
00317 }
00318 
00319 void arm_cfft_radix8by4_f32( arm_cfft_instance_f32 * S, float32_t * p1) 
00320 {
00321     uint32_t    L  = S->fftLen >> 1;
00322     float32_t * pCol1, *pCol2, *pCol3, *pCol4, *pEnd1, *pEnd2, *pEnd3, *pEnd4;
00323     const float32_t *tw2, *tw3, *tw4;
00324     float32_t * p2 = p1 + L;
00325     float32_t * p3 = p2 + L;
00326     float32_t * p4 = p3 + L;
00327     float32_t t2[4], t3[4], t4[4], twR, twI;
00328     float32_t p1ap3_0, p1sp3_0, p1ap3_1, p1sp3_1;
00329     float32_t m0, m1, m2, m3;
00330     uint32_t l, twMod2, twMod3, twMod4;
00331 
00332     pCol1 = p1;         // points to real values by default
00333     pCol2 = p2;
00334     pCol3 = p3;
00335     pCol4 = p4;
00336     pEnd1 = p2 - 1;     // points to imaginary values by default
00337     pEnd2 = p3 - 1;
00338     pEnd3 = p4 - 1;
00339     pEnd4 = pEnd3 + L;
00340 
00341     tw2 = tw3 = tw4 = (float32_t *) S->pTwiddle;
00342 
00343     L >>= 1;
00344 
00345     // do four dot Fourier transform
00346 
00347     twMod2 = 2;
00348     twMod3 = 4;
00349     twMod4 = 6;
00350 
00351     // TOP
00352     p1ap3_0 = p1[0] + p3[0];
00353     p1sp3_0 = p1[0] - p3[0];
00354     p1ap3_1 = p1[1] + p3[1];
00355     p1sp3_1 = p1[1] - p3[1];
00356 
00357     // col 2
00358     t2[0] = p1sp3_0 + p2[1] - p4[1];
00359     t2[1] = p1sp3_1 - p2[0] + p4[0];
00360     // col 3
00361     t3[0] = p1ap3_0 - p2[0] - p4[0];
00362     t3[1] = p1ap3_1 - p2[1] - p4[1];
00363     // col 4
00364     t4[0] = p1sp3_0 - p2[1] + p4[1];
00365     t4[1] = p1sp3_1 + p2[0] - p4[0];
00366     // col 1
00367     *p1++ = p1ap3_0 + p2[0] + p4[0];
00368     *p1++ = p1ap3_1 + p2[1] + p4[1];
00369 
00370     // Twiddle factors are ones
00371     *p2++ = t2[0];
00372     *p2++ = t2[1];
00373     *p3++ = t3[0];
00374     *p3++ = t3[1];
00375     *p4++ = t4[0];
00376     *p4++ = t4[1];
00377 
00378     tw2 += twMod2;
00379     tw3 += twMod3;
00380     tw4 += twMod4;
00381 
00382     for (l = (L - 2) >> 1; l > 0; l-- ) 
00383     {
00384         // TOP
00385         p1ap3_0 = p1[0] + p3[0];
00386         p1sp3_0 = p1[0] - p3[0];
00387         p1ap3_1 = p1[1] + p3[1];
00388         p1sp3_1 = p1[1] - p3[1];
00389         // col 2
00390         t2[0] = p1sp3_0 + p2[1] - p4[1];
00391         t2[1] = p1sp3_1 - p2[0] + p4[0];
00392         // col 3
00393         t3[0] = p1ap3_0 - p2[0] - p4[0];
00394         t3[1] = p1ap3_1 - p2[1] - p4[1];
00395         // col 4
00396         t4[0] = p1sp3_0 - p2[1] + p4[1];
00397         t4[1] = p1sp3_1 + p2[0] - p4[0];
00398         // col 1 - top
00399         *p1++ = p1ap3_0 + p2[0] + p4[0];
00400         *p1++ = p1ap3_1 + p2[1] + p4[1];
00401 
00402         // BOTTOM
00403         p1ap3_1 = pEnd1[-1] + pEnd3[-1];
00404         p1sp3_1 = pEnd1[-1] - pEnd3[-1];
00405         p1ap3_0 = pEnd1[0] + pEnd3[0];
00406         p1sp3_0 = pEnd1[0] - pEnd3[0];
00407         // col 2
00408         t2[2] = pEnd2[0]  - pEnd4[0] + p1sp3_1;
00409         t2[3] = pEnd1[0] - pEnd3[0] - pEnd2[-1] + pEnd4[-1];
00410         // col 3
00411         t3[2] = p1ap3_1 - pEnd2[-1] - pEnd4[-1];
00412         t3[3] = p1ap3_0 - pEnd2[0]  - pEnd4[0];
00413         // col 4
00414         t4[2] = pEnd2[0]  - pEnd4[0]  - p1sp3_1;
00415         t4[3] = pEnd4[-1] - pEnd2[-1] - p1sp3_0;
00416         // col 1 - Bottom
00417         *pEnd1-- = p1ap3_0 + pEnd2[0] + pEnd4[0];
00418         *pEnd1-- = p1ap3_1 + pEnd2[-1] + pEnd4[-1];
00419 
00420         // COL 2
00421         // read twiddle factors
00422         twR = *tw2++;
00423         twI = *tw2++;
00424         // multiply by twiddle factors
00425         //  let    Z1 = a + i(b),   Z2 = c + i(d)
00426         //   =>  Z1 * Z2  =  (a*c - b*d) + i(b*c + a*d)
00427         
00428         // Top
00429         m0 = t2[0] * twR;
00430         m1 = t2[1] * twI;
00431         m2 = t2[1] * twR;
00432         m3 = t2[0] * twI;
00433         
00434         *p2++ = m0 + m1;
00435         *p2++ = m2 - m3;
00436         // use vertical symmetry col 2
00437         // 0.9997 - 0.0245i  <==>  0.0245 - 0.9997i
00438         // Bottom
00439         m0 = t2[3] * twI;
00440         m1 = t2[2] * twR;
00441         m2 = t2[2] * twI;
00442         m3 = t2[3] * twR;
00443         
00444         *pEnd2-- = m0 - m1;
00445         *pEnd2-- = m2 + m3;
00446 
00447         // COL 3
00448         twR = tw3[0];
00449         twI = tw3[1];
00450         tw3 += twMod3;
00451         // Top
00452         m0 = t3[0] * twR;
00453         m1 = t3[1] * twI;
00454         m2 = t3[1] * twR;
00455         m3 = t3[0] * twI;
00456         
00457         *p3++ = m0 + m1;
00458         *p3++ = m2 - m3;
00459         // use vertical symmetry col 3
00460         // 0.9988 - 0.0491i  <==>  -0.9988 - 0.0491i
00461         // Bottom
00462         m0 = -t3[3] * twR;
00463         m1 = t3[2] * twI;
00464         m2 = t3[2] * twR;
00465         m3 = t3[3] * twI;
00466         
00467         *pEnd3-- = m0 - m1;
00468         *pEnd3-- = m3 - m2;
00469         
00470         // COL 4
00471         twR = tw4[0];
00472         twI = tw4[1];
00473         tw4 += twMod4;
00474         // Top
00475         m0 = t4[0] * twR;
00476         m1 = t4[1] * twI;
00477         m2 = t4[1] * twR;
00478         m3 = t4[0] * twI;
00479         
00480         *p4++ = m0 + m1;
00481         *p4++ = m2 - m3;
00482         // use vertical symmetry col 4
00483         // 0.9973 - 0.0736i  <==>  -0.0736 + 0.9973i
00484         // Bottom
00485         m0 = t4[3] * twI;
00486         m1 = t4[2] * twR;
00487         m2 = t4[2] * twI;
00488         m3 = t4[3] * twR;
00489         
00490         *pEnd4-- = m0 - m1;
00491         *pEnd4-- = m2 + m3;
00492     }
00493 
00494     //MIDDLE
00495     // Twiddle factors are 
00496     //  1.0000  0.7071-0.7071i  -1.0000i  -0.7071-0.7071i
00497     p1ap3_0 = p1[0] + p3[0];
00498     p1sp3_0 = p1[0] - p3[0];
00499     p1ap3_1 = p1[1] + p3[1];
00500     p1sp3_1 = p1[1] - p3[1];
00501 
00502     // col 2
00503     t2[0] = p1sp3_0 + p2[1] - p4[1];
00504     t2[1] = p1sp3_1 - p2[0] + p4[0];
00505     // col 3
00506     t3[0] = p1ap3_0 - p2[0] - p4[0];
00507     t3[1] = p1ap3_1 - p2[1] - p4[1];
00508     // col 4
00509     t4[0] = p1sp3_0 - p2[1] + p4[1];
00510     t4[1] = p1sp3_1 + p2[0] - p4[0];
00511     // col 1 - Top
00512     *p1++ = p1ap3_0 + p2[0] + p4[0];
00513     *p1++ = p1ap3_1 + p2[1] + p4[1];
00514 
00515     // COL 2
00516     twR = tw2[0];
00517     twI = tw2[1];
00518 
00519     m0 = t2[0] * twR;
00520     m1 = t2[1] * twI;
00521     m2 = t2[1] * twR;
00522     m3 = t2[0] * twI;
00523 
00524     *p2++ = m0 + m1;
00525     *p2++ = m2 - m3;
00526     // COL 3
00527     twR = tw3[0];
00528     twI = tw3[1];
00529 
00530     m0 = t3[0] * twR;
00531     m1 = t3[1] * twI;
00532     m2 = t3[1] * twR;
00533     m3 = t3[0] * twI;
00534 
00535     *p3++ = m0 + m1;
00536     *p3++ = m2 - m3;
00537     // COL 4
00538     twR = tw4[0];
00539     twI = tw4[1];
00540 
00541     m0 = t4[0] * twR;
00542     m1 = t4[1] * twI;
00543     m2 = t4[1] * twR;
00544     m3 = t4[0] * twI;
00545 
00546     *p4++ = m0 + m1;
00547     *p4++ = m2 - m3;
00548 
00549     // first col
00550     arm_radix8_butterfly_f32( pCol1, L, (float32_t *) S->pTwiddle, 4u);
00551     // second col
00552     arm_radix8_butterfly_f32( pCol2, L, (float32_t *) S->pTwiddle, 4u);
00553     // third col
00554     arm_radix8_butterfly_f32( pCol3, L, (float32_t *) S->pTwiddle, 4u);
00555     // fourth col
00556     arm_radix8_butterfly_f32( pCol4, L, (float32_t *) S->pTwiddle, 4u);
00557 }
00558 
00559 /**
00560 * @addtogroup ComplexFFT   
00561 * @{   
00562 */
00563 
00564 /**   
00565 * @details   
00566 * @brief       Processing function for the floating-point complex FFT.
00567 * @param[in]      *S    points to an instance of the floating-point CFFT structure.  
00568 * @param[in, out] *p1   points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.  
00569 * @param[in]     ifftFlag       flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.  
00570 * @param[in]     bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.  
00571 * @return none.  
00572 */
00573 
00574 void arm_cfft_f32( 
00575     const arm_cfft_instance_f32 * S, 
00576     float32_t * p1,
00577     uint8_t ifftFlag,
00578     uint8_t bitReverseFlag)
00579 {
00580     uint32_t  L = S->fftLen, l;
00581     float32_t invL, * pSrc;
00582 
00583     if(ifftFlag == 1u)
00584     {
00585         /*  Conjugate input data  */
00586         pSrc = p1 + 1;
00587         for(l=0; l<L; l++) 
00588         {
00589             *pSrc = -*pSrc;
00590             pSrc += 2;
00591         }
00592     }
00593 
00594     switch (L) 
00595     {
00596     case 16: 
00597     case 128:
00598     case 1024:
00599         arm_cfft_radix8by2_f32  ( (arm_cfft_instance_f32 *) S, p1);
00600         break;
00601     case 32:
00602     case 256:
00603     case 2048:
00604         arm_cfft_radix8by4_f32  ( (arm_cfft_instance_f32 *) S, p1);
00605         break;
00606     case 64:
00607     case 512:
00608     case 4096:
00609         arm_radix8_butterfly_f32( p1, L, (float32_t *) S->pTwiddle, 1);
00610         break;
00611     }  
00612 
00613     if( bitReverseFlag )
00614         arm_bitreversal_32((uint32_t*)p1,S->bitRevLength,S->pBitRevTable);
00615 
00616     if(ifftFlag == 1u)
00617     {
00618         invL = 1.0f/(float32_t)L;
00619         /*  Conjugate and scale output data */
00620         pSrc = p1;
00621         for(l=0; l<L; l++) 
00622         {
00623             *pSrc++ *=   invL ;
00624             *pSrc  = -(*pSrc) * invL;
00625             pSrc++;
00626         }
00627     }
00628 }
00629 
00630 /**    
00631 * @} end of ComplexFFT group    
00632 */