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    50. 

  50. <h1>arm_cfft_radix4_q15.c</h1>  </div>
    51. 

  51. </div>
    52. 

  52. <div class="contents">
    53. 

  53. <a href="arm__cfft__radix4__q15_8c.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* ----------------------------------------------------------------------   </span>
    54. 

  54. <a name="l00002"></a>00002 <span class="comment">* Copyright (C) 2010 ARM Limited. All rights reserved.   </span>
    55. 

  55. <a name="l00003"></a>00003 <span class="comment">*   </span>
    56. 

  56. <a name="l00004"></a>00004 <span class="comment">* $Date:        15. July 2011  </span>
    57. 

  57. <a name="l00005"></a>00005 <span class="comment">* $Revision:    V1.0.10  </span>
    58. 

  58. <a name="l00006"></a>00006 <span class="comment">*   </span>
    59. 

  59. <a name="l00007"></a>00007 <span class="comment">* Project:      CMSIS DSP Library   </span>
    60. 

  60. <a name="l00008"></a>00008 <span class="comment">* Title:        arm_cfft_radix4_q15.c   </span>
    61. 

  61. <a name="l00009"></a>00009 <span class="comment">*   </span>
    62. 

  62. <a name="l00010"></a>00010 <span class="comment">* Description:  This file has function definition of Radix-4 FFT &amp; IFFT function and   </span>
    63. 

  63. <a name="l00011"></a>00011 <span class="comment">*               In-place bit reversal using bit reversal table   </span>
    64. 

  64. <a name="l00012"></a>00012 <span class="comment">*   </span>
    65. 

  65. <a name="l00013"></a>00013 <span class="comment">* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0</span>
    66. 

  66. <a name="l00014"></a>00014 <span class="comment">*  </span>
    67. 

  67. <a name="l00015"></a>00015 <span class="comment">* Version 1.0.10 2011/7/15 </span>
    68. 

  68. <a name="l00016"></a>00016 <span class="comment">*    Big Endian support added and Merged M0 and M3/M4 Source code.  </span>
    69. 

  69. <a name="l00017"></a>00017 <span class="comment">*   </span>
    70. 

  70. <a name="l00018"></a>00018 <span class="comment">* Version 1.0.3 2010/11/29  </span>
    71. 

  71. <a name="l00019"></a>00019 <span class="comment">*    Re-organized the CMSIS folders and updated documentation.   </span>
    72. 

  72. <a name="l00020"></a>00020 <span class="comment">*    </span>
    73. 

  73. <a name="l00021"></a>00021 <span class="comment">* Version 1.0.2 2010/11/11   </span>
    74. 

  74. <a name="l00022"></a>00022 <span class="comment">*    Documentation updated.    </span>
    75. 

  75. <a name="l00023"></a>00023 <span class="comment">*   </span>
    76. 

  76. <a name="l00024"></a>00024 <span class="comment">* Version 1.0.1 2010/10/05    </span>
    77. 

  77. <a name="l00025"></a>00025 <span class="comment">*    Production release and review comments incorporated.   </span>
    78. 

  78. <a name="l00026"></a>00026 <span class="comment">*   </span>
    79. 

  79. <a name="l00027"></a>00027 <span class="comment">* Version 1.0.0 2010/09/20    </span>
    80. 

  80. <a name="l00028"></a>00028 <span class="comment">*    Production release and review comments incorporated.   </span>
    81. 

  81. <a name="l00029"></a>00029 <span class="comment">*   </span>
    82. 

  82. <a name="l00030"></a>00030 <span class="comment">* Version 0.0.5  2010/04/26    </span>
    83. 

  83. <a name="l00031"></a>00031 <span class="comment">*    incorporated review comments and updated with latest CMSIS layer   </span>
    84. 

  84. <a name="l00032"></a>00032 <span class="comment">*   </span>
    85. 

  85. <a name="l00033"></a>00033 <span class="comment">* Version 0.0.3  2010/03/10    </span>
    86. 

  86. <a name="l00034"></a>00034 <span class="comment">*    Initial version   </span>
    87. 

  87. <a name="l00035"></a>00035 <span class="comment">* -------------------------------------------------------------------- */</span>
    88. 

  88. <a name="l00036"></a>00036 
    89. 

  89. <a name="l00037"></a>00037 <span class="preprocessor">#include &quot;<a class="code" href="arm__math_8h.html">arm_math.h</a>&quot;</span>
    90. 

  90. <a name="l00038"></a>00038 
    91. 

  91. <a name="l00066"></a><a class="code" href="group___c_f_f_t___c_i_f_f_t.html#ga8d66cdac41b8bf6cefdb895456eee84a">00066</a> <span class="keywordtype">void</span> <a class="code" href="group___c_f_f_t___c_i_f_f_t.html#ga8d66cdac41b8bf6cefdb895456eee84a" title="Processing function for the Q15 CFFT/CIFFT.">arm_cfft_radix4_q15</a>(
    92. 

  92. <a name="l00067"></a>00067   <span class="keyword">const</span> <a class="code" href="structarm__cfft__radix4__instance__q15.html" title="Instance structure for the Q15 CFFT/CIFFT function.">arm_cfft_radix4_instance_q15</a> * S,
    93. 

  93. <a name="l00068"></a>00068   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pSrc)
    94. 

  94. <a name="l00069"></a>00069 {
    95. 

  95. <a name="l00070"></a>00070   <span class="keywordflow">if</span>(S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a2ecff6ea735cb4d22e922d0fd5736655">ifftFlag</a> == 1u)
    96. 

  96. <a name="l00071"></a>00071   {
    97. 

  97. <a name="l00072"></a>00072     <span class="comment">/*  Complex IFFT radix-4  */</span>
    98. 

  98. <a name="l00073"></a>00073     <a class="code" href="arm__cfft__radix4__q15_8c.html#aad04e8439d17dab5617bf1be268bb391" title="Core function for the Q15 CIFFT butterfly process.">arm_radix4_butterfly_inverse_q15</a>(pSrc, S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a5fc543e7d84ca8cb7cf6648970f21ca6">fftLen</a>, S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a29dd693537e45421a36891f8439e1fba">pTwiddle</a>,
    99. 

  99. <a name="l00074"></a>00074                                      S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#af32fdc78bcc27ca385f9b76a0a1f71c3">twidCoefModifier</a>);
    100. 

  100. <a name="l00075"></a>00075   }
    101. 

  101. <a name="l00076"></a>00076   <span class="keywordflow">else</span>
    102. 

  102. <a name="l00077"></a>00077   {
    103. 

  103. <a name="l00078"></a>00078     <span class="comment">/*  Complex FFT radix-4  */</span>
    104. 

  104. <a name="l00079"></a>00079     <a class="code" href="arm__cfft__radix4__q15_8c.html#a2d01d2045f280c32036da97d33c52440" title="Core function for the Q15 CFFT butterfly process.">arm_radix4_butterfly_q15</a>(pSrc, S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a5fc543e7d84ca8cb7cf6648970f21ca6">fftLen</a>, S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a29dd693537e45421a36891f8439e1fba">pTwiddle</a>,
    105. 

  105. <a name="l00080"></a>00080                              S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#af32fdc78bcc27ca385f9b76a0a1f71c3">twidCoefModifier</a>);
    106. 

  106. <a name="l00081"></a>00081   }
    107. 

  107. <a name="l00082"></a>00082 
    108. 

  108. <a name="l00083"></a>00083   <span class="keywordflow">if</span>(S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a101e3f7b0bd6b5b14cd5214f23df4133">bitReverseFlag</a> == 1u)
    109. 

  109. <a name="l00084"></a>00084   {
    110. 

  110. <a name="l00085"></a>00085     <span class="comment">/*  Bit Reversal */</span>
    111. 

  111. <a name="l00086"></a>00086     <a class="code" href="arm__cfft__radix4__q15_8c.html#a12a07b49948c354172ae07358309a4a5" title="In-place bit reversal function.">arm_bitreversal_q15</a>(pSrc, S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a5fc543e7d84ca8cb7cf6648970f21ca6">fftLen</a>, S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a6b010e5f02d1130c621e3d2e26b95df1">bitRevFactor</a>, S-&gt;<a class="code" href="structarm__cfft__radix4__instance__q15.html#a4acf704ae0cf30b53bf0fbfae8e34a59">pBitRevTable</a>);
    112. 

  112. <a name="l00087"></a>00087   }
    113. 

  113. <a name="l00088"></a>00088 
    114. 

  114. <a name="l00089"></a>00089 }
    115. 

  115. <a name="l00090"></a>00090 
    116. 

  116. <a name="l00095"></a>00095 <span class="comment">/*   </span>
    117. 

  117. <a name="l00096"></a>00096 <span class="comment">* Radix-4 FFT algorithm used is :   </span>
    118. 

  118. <a name="l00097"></a>00097 <span class="comment">*   </span>
    119. 

  119. <a name="l00098"></a>00098 <span class="comment">* Input real and imaginary data:   </span>
    120. 

  120. <a name="l00099"></a>00099 <span class="comment">* x(n) = xa + j * ya   </span>
    121. 

  121. <a name="l00100"></a>00100 <span class="comment">* x(n+N/4 ) = xb + j * yb   </span>
    122. 

  122. <a name="l00101"></a>00101 <span class="comment">* x(n+N/2 ) = xc + j * yc   </span>
    123. 

  123. <a name="l00102"></a>00102 <span class="comment">* x(n+3N 4) = xd + j * yd   </span>
    124. 

  124. <a name="l00103"></a>00103 <span class="comment">*   </span>
    125. 

  125. <a name="l00104"></a>00104 <span class="comment">*   </span>
    126. 

  126. <a name="l00105"></a>00105 <span class="comment">* Output real and imaginary data:   </span>
    127. 

  127. <a name="l00106"></a>00106 <span class="comment">* x(4r) = xa&#39;+ j * ya&#39;   </span>
    128. 

  128. <a name="l00107"></a>00107 <span class="comment">* x(4r+1) = xb&#39;+ j * yb&#39;   </span>
    129. 

  129. <a name="l00108"></a>00108 <span class="comment">* x(4r+2) = xc&#39;+ j * yc&#39;   </span>
    130. 

  130. <a name="l00109"></a>00109 <span class="comment">* x(4r+3) = xd&#39;+ j * yd&#39;   </span>
    131. 

  131. <a name="l00110"></a>00110 <span class="comment">*   </span>
    132. 

  132. <a name="l00111"></a>00111 <span class="comment">*   </span>
    133. 

  133. <a name="l00112"></a>00112 <span class="comment">* Twiddle factors for radix-4 FFT:   </span>
    134. 

  134. <a name="l00113"></a>00113 <span class="comment">* Wn = co1 + j * (- si1)   </span>
    135. 

  135. <a name="l00114"></a>00114 <span class="comment">* W2n = co2 + j * (- si2)   </span>
    136. 

  136. <a name="l00115"></a>00115 <span class="comment">* W3n = co3 + j * (- si3)   </span>
    137. 

  137. <a name="l00116"></a>00116 <span class="comment">   </span>
    138. 

  138. <a name="l00117"></a>00117 <span class="comment">* The real and imaginary output values for the radix-4 butterfly are   </span>
    139. 

  139. <a name="l00118"></a>00118 <span class="comment">* xa&#39; = xa + xb + xc + xd   </span>
    140. 

  140. <a name="l00119"></a>00119 <span class="comment">* ya&#39; = ya + yb + yc + yd   </span>
    141. 

  141. <a name="l00120"></a>00120 <span class="comment">* xb&#39; = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1)   </span>
    142. 

  142. <a name="l00121"></a>00121 <span class="comment">* yb&#39; = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1)   </span>
    143. 

  143. <a name="l00122"></a>00122 <span class="comment">* xc&#39; = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2)   </span>
    144. 

  144. <a name="l00123"></a>00123 <span class="comment">* yc&#39; = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2)   </span>
    145. 

  145. <a name="l00124"></a>00124 <span class="comment">* xd&#39; = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3)   </span>
    146. 

  146. <a name="l00125"></a>00125 <span class="comment">* yd&#39; = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3)   </span>
    147. 

  147. <a name="l00126"></a>00126 <span class="comment">*   </span>
    148. 

  148. <a name="l00127"></a>00127 <span class="comment">*/</span>
    149. 

  149. <a name="l00128"></a>00128 
    150. 

  150. <a name="l00138"></a><a class="code" href="arm__math_8h.html#a2d01d2045f280c32036da97d33c52440">00138</a> <span class="keywordtype">void</span> <a class="code" href="arm__cfft__radix4__q15_8c.html#a2d01d2045f280c32036da97d33c52440" title="Core function for the Q15 CFFT butterfly process.">arm_radix4_butterfly_q15</a>(
    151. 

  151. <a name="l00139"></a>00139   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pSrc16,
    152. 

  152. <a name="l00140"></a>00140   uint32_t fftLen,
    153. 

  153. <a name="l00141"></a>00141   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pCoef16,
    154. 

  154. <a name="l00142"></a>00142   uint32_t twidCoefModifier)
    155. 

  155. <a name="l00143"></a>00143 {
    156. 

  156. <a name="l00144"></a>00144 
    157. 

  157. <a name="l00145"></a>00145 <span class="preprocessor">#ifndef ARM_MATH_CM0</span>
    158. 

  158. <a name="l00146"></a>00146 <span class="preprocessor"></span>
    159. 

  159. <a name="l00147"></a>00147   <span class="comment">/* Run the below code for Cortex-M4 and Cortex-M3 */</span>
    160. 

  160. <a name="l00148"></a>00148 
    161. 

  161. <a name="l00149"></a>00149   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> R, S, T, U;
    162. 

  162. <a name="l00150"></a>00150   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> C1, C2, C3, out1, out2;
    163. 

  163. <a name="l00151"></a>00151   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *pSrc, *pCoeff;
    164. 

  164. <a name="l00152"></a>00152   uint32_t n1, n2, ic, i0, i1, i2, i3, j, k;
    165. 

  165. <a name="l00153"></a>00153   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> in;
    166. 

  166. <a name="l00154"></a>00154 
    167. 

  167. <a name="l00155"></a>00155   <span class="comment">/* Total process is divided into three stages */</span>
    168. 

  168. <a name="l00156"></a>00156 
    169. 

  169. <a name="l00157"></a>00157   <span class="comment">/* process first stage, middle stages, &amp; last stage */</span>
    170. 

  170. <a name="l00158"></a>00158 
    171. 

  171. <a name="l00159"></a>00159   <span class="comment">/*  pointer initializations for SIMD calculations */</span>
    172. 

  172. <a name="l00160"></a>00160   pSrc = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *) pSrc16;
    173. 

  173. <a name="l00161"></a>00161   pCoeff = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *) pCoef16;
    174. 

  174. <a name="l00162"></a>00162 
    175. 

  175. <a name="l00163"></a>00163   <span class="comment">/*  Initializations for the first stage */</span>
    176. 

  176. <a name="l00164"></a>00164   n2 = fftLen;
    177. 

  177. <a name="l00165"></a>00165   n1 = n2;
    178. 

  178. <a name="l00166"></a>00166 
    179. 

  179. <a name="l00167"></a>00167   <span class="comment">/* n2 = fftLen/4 */</span>
    180. 

  180. <a name="l00168"></a>00168   n2 &gt;&gt;= 2u;
    181. 

  181. <a name="l00169"></a>00169 
    182. 

  182. <a name="l00170"></a>00170   <span class="comment">/* Index for twiddle coefficient */</span>
    183. 

  183. <a name="l00171"></a>00171   ic = 0u;
    184. 

  184. <a name="l00172"></a>00172 
    185. 

  185. <a name="l00173"></a>00173   <span class="comment">/* Index for input read and output write */</span>
    186. 

  186. <a name="l00174"></a>00174   i0 = 0u;
    187. 

  187. <a name="l00175"></a>00175   j = n2;
    188. 

  188. <a name="l00176"></a>00176 
    189. 

  189. <a name="l00177"></a>00177   <span class="comment">/* Input is in 1.15(q15) format */</span>
    190. 

  190. <a name="l00178"></a>00178 
    191. 

  191. <a name="l00179"></a>00179   <span class="comment">/*  start of first stage process */</span>
    192. 

  192. <a name="l00180"></a>00180   <span class="keywordflow">do</span>
    193. 

  193. <a name="l00181"></a>00181   {
    194. 

  194. <a name="l00182"></a>00182     <span class="comment">/*  Butterfly implementation */</span>
    195. 

  195. <a name="l00183"></a>00183 
    196. 

  196. <a name="l00184"></a>00184     <span class="comment">/*  index calculation for the input as, */</span>
    197. 

  197. <a name="l00185"></a>00185     <span class="comment">/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */</span>
    198. 

  198. <a name="l00186"></a>00186     i1 = i0 + n2;
    199. 

  199. <a name="l00187"></a>00187     i2 = i1 + n2;
    200. 

  200. <a name="l00188"></a>00188     i3 = i2 + n2;
    201. 

  201. <a name="l00189"></a>00189 
    202. 

  202. <a name="l00190"></a>00190     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    203. 

  203. <a name="l00191"></a>00191     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    204. 

  204. <a name="l00192"></a>00192     T = pSrc[i0];
    205. 

  205. <a name="l00193"></a>00193     in = ((int16_t) (T &amp; 0xFFFF)) &gt;&gt; 2;
    206. 

  206. <a name="l00194"></a>00194     T = ((T &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    207. 

  207. <a name="l00195"></a>00195     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    208. 

  208. <a name="l00196"></a>00196     S = pSrc[i2];
    209. 

  209. <a name="l00197"></a>00197     in = ((int16_t) (S &amp; 0xFFFF)) &gt;&gt; 2;
    210. 

  210. <a name="l00198"></a>00198     S = ((S &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    211. 

  211. <a name="l00199"></a>00199     <span class="comment">/* R = packed((ya + yc), (xa + xc) ) */</span>
    212. 

  212. <a name="l00200"></a>00200     R = __QADD16(T, S);
    213. 

  213. <a name="l00201"></a>00201     <span class="comment">/* S = packed((ya - yc), (xa - xc) ) */</span>
    214. 

  214. <a name="l00202"></a>00202     S = __QSUB16(T, S);
    215. 

  215. <a name="l00203"></a>00203 
    216. 

  216. <a name="l00204"></a>00204     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    217. 

  217. <a name="l00205"></a>00205     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    218. 

  218. <a name="l00206"></a>00206     T = pSrc[i1];
    219. 

  219. <a name="l00207"></a>00207     in = ((int16_t) (T &amp; 0xFFFF)) &gt;&gt; 2;
    220. 

  220. <a name="l00208"></a>00208     T = ((T &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    221. 

  221. <a name="l00209"></a>00209     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    222. 

  222. <a name="l00210"></a>00210     U = pSrc[i3];
    223. 

  223. <a name="l00211"></a>00211     in = ((int16_t) (U &amp; 0xFFFF)) &gt;&gt; 2;
    224. 

  224. <a name="l00212"></a>00212     U = ((U &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    225. 

  225. <a name="l00213"></a>00213     <span class="comment">/* T = packed((yb + yd), (xb + xd) ) */</span>
    226. 

  226. <a name="l00214"></a>00214     T = __QADD16(T, U);
    227. 

  227. <a name="l00215"></a>00215 
    228. 

  228. <a name="l00216"></a>00216     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    229. 

  229. <a name="l00217"></a>00217     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    230. 

  230. <a name="l00218"></a>00218     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    231. 

  231. <a name="l00219"></a>00219     pSrc[i0] = __SHADD16(R, T);
    232. 

  232. <a name="l00220"></a>00220 
    233. 

  233. <a name="l00221"></a>00221     <span class="comment">/* R = packed((ya + yc) - (yb + yd), (xa + xc)- (xb + xd)) */</span>
    234. 

  234. <a name="l00222"></a>00222     R = __QSUB16(R, T);
    235. 

  235. <a name="l00223"></a>00223 
    236. 

  236. <a name="l00224"></a>00224     <span class="comment">/* co2 &amp; si2 are read from SIMD Coefficient pointer */</span>
    237. 

  237. <a name="l00225"></a>00225     C2 = pCoeff[2u * ic];
    238. 

  238. <a name="l00226"></a>00226 
    239. 

  239. <a name="l00227"></a>00227 
    240. 

  240. <a name="l00228"></a>00228 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    241. 

  241. <a name="l00229"></a>00229 <span class="preprocessor"></span>
    242. 

  242. <a name="l00230"></a>00230     <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */</span>
    243. 

  243. <a name="l00231"></a>00231     out1 = __SMUAD(C2, R) &gt;&gt; 16u;
    244. 

  244. <a name="l00232"></a>00232     <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    245. 

  245. <a name="l00233"></a>00233     out2 = __SMUSDX(C2, R);
    246. 

  246. <a name="l00234"></a>00234 
    247. 

  247. <a name="l00235"></a>00235 <span class="preprocessor">#else</span>
    248. 

  248. <a name="l00236"></a>00236 <span class="preprocessor"></span>
    249. 

  249. <a name="l00237"></a>00237     <span class="comment">/* xc&#39; = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    250. 

  250. <a name="l00238"></a>00238     out1 = __SMUSDX(R, C2) &gt;&gt; 16u;
    251. 

  251. <a name="l00239"></a>00239     <span class="comment">/* yc&#39; = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */</span>
    252. 

  252. <a name="l00240"></a>00240     out2 = __SMUAD(C2, R);
    253. 

  253. <a name="l00241"></a>00241 
    254. 

  254. <a name="l00242"></a>00242 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    255. 

  255. <a name="l00243"></a>00243 
    256. 

  256. <a name="l00244"></a>00244     <span class="comment">/*  Reading i0+fftLen/4 */</span>
    257. 

  257. <a name="l00245"></a>00245     <span class="comment">/* T = packed(yb, xb) */</span>
    258. 

  258. <a name="l00246"></a>00246     T = pSrc[i1];
    259. 

  259. <a name="l00247"></a>00247     in = ((int16_t) (T &amp; 0xFFFF)) &gt;&gt; 2;
    260. 

  260. <a name="l00248"></a>00248     T = ((T &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    261. 

  261. <a name="l00249"></a>00249 
    262. 

  262. <a name="l00250"></a>00250     <span class="comment">/* writing the butterfly processed i0 + fftLen/4 sample */</span>
    263. 

  263. <a name="l00251"></a>00251     <span class="comment">/* writing output(xc&#39;, yc&#39;) in little endian format */</span>
    264. 

  264. <a name="l00252"></a>00252     pSrc[i1] = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    265. 

  265. <a name="l00253"></a>00253 
    266. 

  266. <a name="l00254"></a>00254     <span class="comment">/*  Butterfly calculations */</span>
    267. 

  267. <a name="l00255"></a>00255     <span class="comment">/* U = packed(yd, xd) */</span>
    268. 

  268. <a name="l00256"></a>00256     U = pSrc[i3];
    269. 

  269. <a name="l00257"></a>00257     in = ((int16_t) (U &amp; 0xFFFF)) &gt;&gt; 2;
    270. 

  270. <a name="l00258"></a>00258     U = ((U &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    271. 

  271. <a name="l00259"></a>00259     <span class="comment">/* T = packed(yb-yd, xb-xd) */</span>
    272. 

  272. <a name="l00260"></a>00260     T = __QSUB16(T, U);
    273. 

  273. <a name="l00261"></a>00261 
    274. 

  274. <a name="l00262"></a>00262 
    275. 

  275. <a name="l00263"></a>00263 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    276. 

  276. <a name="l00264"></a>00264 <span class="preprocessor"></span>
    277. 

  277. <a name="l00265"></a>00265     <span class="comment">/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */</span>
    278. 

  278. <a name="l00266"></a>00266     R = __QASX(S, T);
    279. 

  279. <a name="l00267"></a>00267     <span class="comment">/* S = packed((ya-yc) - (xb- xd),  (xa-xc) + (yb-yd)) */</span>
    280. 

  280. <a name="l00268"></a>00268     S = __QSAX(S, T);
    281. 

  281. <a name="l00269"></a>00269 
    282. 

  282. <a name="l00270"></a>00270 <span class="preprocessor">#else</span>
    283. 

  283. <a name="l00271"></a>00271 <span class="preprocessor"></span>
    284. 

  284. <a name="l00272"></a>00272     <span class="comment">/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */</span>
    285. 

  285. <a name="l00273"></a>00273     R = __QSAX(S, T);
    286. 

  286. <a name="l00274"></a>00274     <span class="comment">/* S = packed((ya-yc) - (xb- xd),  (xa-xc) + (yb-yd)) */</span>
    287. 

  287. <a name="l00275"></a>00275     S = __QASX(S, T);
    288. 

  288. <a name="l00276"></a>00276 
    289. 

  289. <a name="l00277"></a>00277 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    290. 

  290. <a name="l00278"></a>00278 
    291. 

  291. <a name="l00279"></a>00279     <span class="comment">/* co1 &amp; si1 are read from SIMD Coefficient pointer */</span>
    292. 

  292. <a name="l00280"></a>00280     C1 = pCoeff[ic];
    293. 

  293. <a name="l00281"></a>00281     <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    294. 

  294. <a name="l00282"></a>00282 
    295. 

  295. <a name="l00283"></a>00283 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    296. 

  296. <a name="l00284"></a>00284 <span class="preprocessor"></span>
    297. 

  297. <a name="l00285"></a>00285     <span class="comment">/* xb&#39; = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */</span>
    298. 

  298. <a name="l00286"></a>00286     out1 = __SMUAD(C1, S) &gt;&gt; 16u;
    299. 

  299. <a name="l00287"></a>00287     <span class="comment">/* yb&#39; = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */</span>
    300. 

  300. <a name="l00288"></a>00288     out2 = __SMUSDX(C1, S);
    301. 

  301. <a name="l00289"></a>00289 
    302. 

  302. <a name="l00290"></a>00290 <span class="preprocessor">#else</span>
    303. 

  303. <a name="l00291"></a>00291 <span class="preprocessor"></span>
    304. 

  304. <a name="l00292"></a>00292     <span class="comment">/* xb&#39; = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */</span>
    305. 

  305. <a name="l00293"></a>00293     out1 = __SMUSDX(S, C1) &gt;&gt; 16u;
    306. 

  306. <a name="l00294"></a>00294     <span class="comment">/* yb&#39; = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */</span>
    307. 

  307. <a name="l00295"></a>00295     out2 = __SMUAD(C1, S);
    308. 

  308. <a name="l00296"></a>00296 
    309. 

  309. <a name="l00297"></a>00297 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    310. 

  310. <a name="l00298"></a>00298 
    311. 

  311. <a name="l00299"></a>00299     <span class="comment">/* writing output(xb&#39;, yb&#39;) in little endian format */</span>
    312. 

  312. <a name="l00300"></a>00300     pSrc[i2] = ((out2) &amp; 0xFFFF0000) | ((out1) &amp; 0x0000FFFF);
    313. 

  313. <a name="l00301"></a>00301 
    314. 

  314. <a name="l00302"></a>00302 
    315. 

  315. <a name="l00303"></a>00303     <span class="comment">/* co3 &amp; si3 are read from SIMD Coefficient pointer */</span>
    316. 

  316. <a name="l00304"></a>00304     C3 = pCoeff[3u * ic];
    317. 

  317. <a name="l00305"></a>00305     <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    318. 

  318. <a name="l00306"></a>00306 
    319. 

  319. <a name="l00307"></a>00307 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    320. 

  320. <a name="l00308"></a>00308 <span class="preprocessor"></span>
    321. 

  321. <a name="l00309"></a>00309     <span class="comment">/* xd&#39; = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */</span>
    322. 

  322. <a name="l00310"></a>00310     out1 = __SMUAD(C3, R) &gt;&gt; 16u;
    323. 

  323. <a name="l00311"></a>00311     <span class="comment">/* yd&#39; = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */</span>
    324. 

  324. <a name="l00312"></a>00312     out2 = __SMUSDX(C3, R);
    325. 

  325. <a name="l00313"></a>00313 
    326. 

  326. <a name="l00314"></a>00314 <span class="preprocessor">#else</span>
    327. 

  327. <a name="l00315"></a>00315 <span class="preprocessor"></span>
    328. 

  328. <a name="l00316"></a>00316     <span class="comment">/* xd&#39; = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */</span>
    329. 

  329. <a name="l00317"></a>00317     out1 = __SMUSDX(R, C3) &gt;&gt; 16u;
    330. 

  330. <a name="l00318"></a>00318     <span class="comment">/* yd&#39; = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */</span>
    331. 

  331. <a name="l00319"></a>00319     out2 = __SMUAD(C3, R);
    332. 

  332. <a name="l00320"></a>00320 
    333. 

  333. <a name="l00321"></a>00321 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    334. 

  334. <a name="l00322"></a>00322 
    335. 

  335. <a name="l00323"></a>00323     <span class="comment">/* writing output(xd&#39;, yd&#39;) in little endian format */</span>
    336. 

  336. <a name="l00324"></a>00324     pSrc[i3] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    337. 

  337. <a name="l00325"></a>00325 
    338. 

  338. <a name="l00326"></a>00326     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    339. 

  339. <a name="l00327"></a>00327     ic = ic + twidCoefModifier;
    340. 

  340. <a name="l00328"></a>00328 
    341. 

  341. <a name="l00329"></a>00329     <span class="comment">/*  Updating input index */</span>
    342. 

  342. <a name="l00330"></a>00330     i0 = i0 + 1u;
    343. 

  343. <a name="l00331"></a>00331 
    344. 

  344. <a name="l00332"></a>00332   } <span class="keywordflow">while</span>(--j);
    345. 

  345. <a name="l00333"></a>00333   <span class="comment">/* data is in 4.11(q11) format */</span>
    346. 

  346. <a name="l00334"></a>00334 
    347. 

  347. <a name="l00335"></a>00335   <span class="comment">/* end of first stage process */</span>
    348. 

  348. <a name="l00336"></a>00336 
    349. 

  349. <a name="l00337"></a>00337 
    350. 

  350. <a name="l00338"></a>00338   <span class="comment">/* start of middle stage process */</span>
    351. 

  351. <a name="l00339"></a>00339 
    352. 

  352. <a name="l00340"></a>00340   <span class="comment">/*  Twiddle coefficients index modifier */</span>
    353. 

  353. <a name="l00341"></a>00341   twidCoefModifier &lt;&lt;= 2u;
    354. 

  354. <a name="l00342"></a>00342 
    355. 

  355. <a name="l00343"></a>00343   <span class="comment">/*  Calculation of Middle stage */</span>
    356. 

  356. <a name="l00344"></a>00344   <span class="keywordflow">for</span> (k = fftLen / 4u; k &gt; 4u; k &gt;&gt;= 2u)
    357. 

  357. <a name="l00345"></a>00345   {
    358. 

  358. <a name="l00346"></a>00346     <span class="comment">/*  Initializations for the middle stage */</span>
    359. 

  359. <a name="l00347"></a>00347     n1 = n2;
    360. 

  360. <a name="l00348"></a>00348     n2 &gt;&gt;= 2u;
    361. 

  361. <a name="l00349"></a>00349     ic = 0u;
    362. 

  362. <a name="l00350"></a>00350 
    363. 

  363. <a name="l00351"></a>00351     <span class="keywordflow">for</span> (j = 0u; j &lt;= (n2 - 1u); j++)
    364. 

  364. <a name="l00352"></a>00352     {
    365. 

  365. <a name="l00353"></a>00353       <span class="comment">/*  index calculation for the coefficients */</span>
    366. 

  366. <a name="l00354"></a>00354       C1 = pCoeff[ic];
    367. 

  367. <a name="l00355"></a>00355       C2 = pCoeff[2u * ic];
    368. 

  368. <a name="l00356"></a>00356       C3 = pCoeff[3u * ic];
    369. 

  369. <a name="l00357"></a>00357 
    370. 

  370. <a name="l00358"></a>00358       <span class="comment">/*  Twiddle coefficients index modifier */</span>
    371. 

  371. <a name="l00359"></a>00359       ic = ic + twidCoefModifier;
    372. 

  372. <a name="l00360"></a>00360 
    373. 

  373. <a name="l00361"></a>00361       <span class="comment">/*  Butterfly implementation */</span>
    374. 

  374. <a name="l00362"></a>00362       <span class="keywordflow">for</span> (i0 = j; i0 &lt; fftLen; i0 += n1)
    375. 

  375. <a name="l00363"></a>00363       {
    376. 

  376. <a name="l00364"></a>00364         <span class="comment">/*  index calculation for the input as, */</span>
    377. 

  377. <a name="l00365"></a>00365         <span class="comment">/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */</span>
    378. 

  378. <a name="l00366"></a>00366         i1 = i0 + n2;
    379. 

  379. <a name="l00367"></a>00367         i2 = i1 + n2;
    380. 

  380. <a name="l00368"></a>00368         i3 = i2 + n2;
    381. 

  381. <a name="l00369"></a>00369 
    382. 

  382. <a name="l00370"></a>00370         <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    383. 

  383. <a name="l00371"></a>00371         <span class="comment">/* Read ya (real), xa(imag) input */</span>
    384. 

  384. <a name="l00372"></a>00372         T = pSrc[i0];
    385. 

  385. <a name="l00373"></a>00373 
    386. 

  386. <a name="l00374"></a>00374         <span class="comment">/* Read yc (real), xc(imag) input */</span>
    387. 

  387. <a name="l00375"></a>00375         S = pSrc[i2];
    388. 

  388. <a name="l00376"></a>00376 
    389. 

  389. <a name="l00377"></a>00377         <span class="comment">/* R = packed( (ya + yc), (xa + xc)) */</span>
    390. 

  390. <a name="l00378"></a>00378         R = __QADD16(T, S);
    391. 

  391. <a name="l00379"></a>00379 
    392. 

  392. <a name="l00380"></a>00380         <span class="comment">/* S = packed((ya - yc), (xa - xc)) */</span>
    393. 

  393. <a name="l00381"></a>00381         S = __QSUB16(T, S);
    394. 

  394. <a name="l00382"></a>00382 
    395. 

  395. <a name="l00383"></a>00383         <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    396. 

  396. <a name="l00384"></a>00384         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    397. 

  397. <a name="l00385"></a>00385         T = pSrc[i1];
    398. 

  398. <a name="l00386"></a>00386 
    399. 

  399. <a name="l00387"></a>00387         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    400. 

  400. <a name="l00388"></a>00388         U = pSrc[i3];
    401. 

  401. <a name="l00389"></a>00389 
    402. 

  402. <a name="l00390"></a>00390 
    403. 

  403. <a name="l00391"></a>00391         <span class="comment">/* T = packed( (yb + yd), (xb + xd)) */</span>
    404. 

  404. <a name="l00392"></a>00392         T = __QADD16(T, U);
    405. 

  405. <a name="l00393"></a>00393 
    406. 

  406. <a name="l00394"></a>00394 
    407. 

  407. <a name="l00395"></a>00395         <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    408. 

  408. <a name="l00396"></a>00396 
    409. 

  409. <a name="l00397"></a>00397         <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    410. 

  410. <a name="l00398"></a>00398         <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    411. 

  411. <a name="l00399"></a>00399         out1 = __SHADD16(R, T);
    412. 

  412. <a name="l00400"></a>00400         in = ((int16_t) (out1 &amp; 0xFFFF)) &gt;&gt; 1;
    413. 

  413. <a name="l00401"></a>00401         out1 = ((out1 &gt;&gt; 1) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    414. 

  414. <a name="l00402"></a>00402         pSrc[i0] = out1;
    415. 

  415. <a name="l00403"></a>00403 
    416. 

  416. <a name="l00404"></a>00404         <span class="comment">/* R = packed( (ya + yc) - (yb + yd), (xa + xc) - (xb + xd)) */</span>
    417. 

  417. <a name="l00405"></a>00405         R = __SHSUB16(R, T);
    418. 

  418. <a name="l00406"></a>00406 
    419. 

  419. <a name="l00407"></a>00407 
    420. 

  420. <a name="l00408"></a>00408 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    421. 

  421. <a name="l00409"></a>00409 <span class="preprocessor"></span>
    422. 

  422. <a name="l00410"></a>00410         <span class="comment">/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */</span>
    423. 

  423. <a name="l00411"></a>00411         out1 = __SMUAD(C2, R) &gt;&gt; 16u;
    424. 

  424. <a name="l00412"></a>00412 
    425. 

  425. <a name="l00413"></a>00413         <span class="comment">/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    426. 

  426. <a name="l00414"></a>00414         out2 = __SMUSDX(C2, R);
    427. 

  427. <a name="l00415"></a>00415 
    428. 

  428. <a name="l00416"></a>00416 <span class="preprocessor">#else</span>
    429. 

  429. <a name="l00417"></a>00417 <span class="preprocessor"></span>
    430. 

  430. <a name="l00418"></a>00418         <span class="comment">/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    431. 

  431. <a name="l00419"></a>00419         out1 = __SMUSDX(R, C2) &gt;&gt; 16u;
    432. 

  432. <a name="l00420"></a>00420 
    433. 

  433. <a name="l00421"></a>00421         <span class="comment">/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */</span>
    434. 

  434. <a name="l00422"></a>00422         out2 = __SMUAD(C2, R);
    435. 

  435. <a name="l00423"></a>00423 
    436. 

  436. <a name="l00424"></a>00424 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    437. 

  437. <a name="l00425"></a>00425 
    438. 

  438. <a name="l00426"></a>00426         <span class="comment">/*  Reading i0+3fftLen/4 */</span>
    439. 

  439. <a name="l00427"></a>00427         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    440. 

  440. <a name="l00428"></a>00428         T = pSrc[i1];
    441. 

  441. <a name="l00429"></a>00429 
    442. 

  442. <a name="l00430"></a>00430         <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    443. 

  443. <a name="l00431"></a>00431         <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */</span>
    444. 

  444. <a name="l00432"></a>00432         <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    445. 

  445. <a name="l00433"></a>00433         pSrc[i1] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    446. 

  446. <a name="l00434"></a>00434 
    447. 

  447. <a name="l00435"></a>00435         <span class="comment">/*  Butterfly calculations */</span>
    448. 

  448. <a name="l00436"></a>00436 
    449. 

  449. <a name="l00437"></a>00437         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    450. 

  450. <a name="l00438"></a>00438         U = pSrc[i3];
    451. 

  451. <a name="l00439"></a>00439 
    452. 

  452. <a name="l00440"></a>00440         <span class="comment">/* T = packed(yb-yd, xb-xd) */</span>
    453. 

  453. <a name="l00441"></a>00441         T = __QSUB16(T, U);
    454. 

  454. <a name="l00442"></a>00442 
    455. 

  455. <a name="l00443"></a>00443 
    456. 

  456. <a name="l00444"></a>00444 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    457. 

  457. <a name="l00445"></a>00445 <span class="preprocessor"></span>
    458. 

  458. <a name="l00446"></a>00446         <span class="comment">/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */</span>
    459. 

  459. <a name="l00447"></a>00447         R = __SHASX(S, T);
    460. 

  460. <a name="l00448"></a>00448 
    461. 

  461. <a name="l00449"></a>00449         <span class="comment">/* S = packed((ya-yc) - (xb- xd),  (xa-xc) + (yb-yd)) */</span>
    462. 

  462. <a name="l00450"></a>00450         S = __SHSAX(S, T);
    463. 

  463. <a name="l00451"></a>00451 
    464. 

  464. <a name="l00452"></a>00452 
    465. 

  465. <a name="l00453"></a>00453         <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    466. 

  466. <a name="l00454"></a>00454         out1 = __SMUAD(C1, S) &gt;&gt; 16u;
    467. 

  467. <a name="l00455"></a>00455         out2 = __SMUSDX(C1, S);
    468. 

  468. <a name="l00456"></a>00456 
    469. 

  469. <a name="l00457"></a>00457 <span class="preprocessor">#else</span>
    470. 

  470. <a name="l00458"></a>00458 <span class="preprocessor"></span>
    471. 

  471. <a name="l00459"></a>00459         <span class="comment">/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */</span>
    472. 

  472. <a name="l00460"></a>00460         R = __SHSAX(S, T);
    473. 

  473. <a name="l00461"></a>00461 
    474. 

  474. <a name="l00462"></a>00462         <span class="comment">/* S = packed((ya-yc) - (xb- xd),  (xa-xc) + (yb-yd)) */</span>
    475. 

  475. <a name="l00463"></a>00463         S = __SHASX(S, T);
    476. 

  476. <a name="l00464"></a>00464 
    477. 

  477. <a name="l00465"></a>00465 
    478. 

  478. <a name="l00466"></a>00466         <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    479. 

  479. <a name="l00467"></a>00467         out1 = __SMUSDX(S, C1) &gt;&gt; 16u;
    480. 

  480. <a name="l00468"></a>00468         out2 = __SMUAD(C1, S);
    481. 

  481. <a name="l00469"></a>00469 
    482. 

  482. <a name="l00470"></a>00470 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    483. 

  483. <a name="l00471"></a>00471 
    484. 

  484. <a name="l00472"></a>00472         <span class="comment">/* xb&#39; = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */</span>
    485. 

  485. <a name="l00473"></a>00473         <span class="comment">/* yb&#39; = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */</span>
    486. 

  486. <a name="l00474"></a>00474         pSrc[i2] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    487. 

  487. <a name="l00475"></a>00475 
    488. 

  488. <a name="l00476"></a>00476         <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    489. 

  489. <a name="l00477"></a>00477 
    490. 

  490. <a name="l00478"></a>00478 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    491. 

  491. <a name="l00479"></a>00479 <span class="preprocessor"></span>
    492. 

  492. <a name="l00480"></a>00480         out1 = __SMUAD(C3, R) &gt;&gt; 16u;
    493. 

  493. <a name="l00481"></a>00481         out2 = __SMUSDX(C3, R);
    494. 

  494. <a name="l00482"></a>00482 
    495. 

  495. <a name="l00483"></a>00483 <span class="preprocessor">#else</span>
    496. 

  496. <a name="l00484"></a>00484 <span class="preprocessor"></span>
    497. 

  497. <a name="l00485"></a>00485         out1 = __SMUSDX(R, C3) &gt;&gt; 16u;
    498. 

  498. <a name="l00486"></a>00486         out2 = __SMUAD(C3, R);
    499. 

  499. <a name="l00487"></a>00487 
    500. 

  500. <a name="l00488"></a>00488 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    501. 

  501. <a name="l00489"></a>00489 
    502. 

  502. <a name="l00490"></a>00490         <span class="comment">/* xd&#39; = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */</span>
    503. 

  503. <a name="l00491"></a>00491         <span class="comment">/* yd&#39; = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */</span>
    504. 

  504. <a name="l00492"></a>00492         pSrc[i3] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    505. 

  505. <a name="l00493"></a>00493       }
    506. 

  506. <a name="l00494"></a>00494     }
    507. 

  507. <a name="l00495"></a>00495     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    508. 

  508. <a name="l00496"></a>00496     twidCoefModifier &lt;&lt;= 2u;
    509. 

  509. <a name="l00497"></a>00497   }
    510. 

  510. <a name="l00498"></a>00498   <span class="comment">/* end of middle stage process */</span>
    511. 

  511. <a name="l00499"></a>00499 
    512. 

  512. <a name="l00500"></a>00500 
    513. 

  513. <a name="l00501"></a>00501   <span class="comment">/* data is in 10.6(q6) format for the 1024 point */</span>
    514. 

  514. <a name="l00502"></a>00502   <span class="comment">/* data is in 8.8(q8) format for the 256 point */</span>
    515. 

  515. <a name="l00503"></a>00503   <span class="comment">/* data is in 6.10(q10) format for the 64 point */</span>
    516. 

  516. <a name="l00504"></a>00504   <span class="comment">/* data is in 4.12(q12) format for the 16 point */</span>
    517. 

  517. <a name="l00505"></a>00505 
    518. 

  518. <a name="l00506"></a>00506   <span class="comment">/*  Initializations for the last stage */</span>
    519. 

  519. <a name="l00507"></a>00507   n1 = n2;
    520. 

  520. <a name="l00508"></a>00508   n2 &gt;&gt;= 2u;
    521. 

  521. <a name="l00509"></a>00509 
    522. 

  522. <a name="l00510"></a>00510   <span class="comment">/* start of last stage process */</span>
    523. 

  523. <a name="l00511"></a>00511 
    524. 

  524. <a name="l00512"></a>00512   <span class="comment">/*  Butterfly implementation */</span>
    525. 

  525. <a name="l00513"></a>00513   <span class="keywordflow">for</span> (i0 = 0u; i0 &lt;= (fftLen - n1); i0 += n1)
    526. 

  526. <a name="l00514"></a>00514   {
    527. 

  527. <a name="l00515"></a>00515     <span class="comment">/*  index calculation for the input as, */</span>
    528. 

  528. <a name="l00516"></a>00516     <span class="comment">/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */</span>
    529. 

  529. <a name="l00517"></a>00517     i1 = i0 + n2;
    530. 

  530. <a name="l00518"></a>00518     i2 = i1 + n2;
    531. 

  531. <a name="l00519"></a>00519     i3 = i2 + n2;
    532. 

  532. <a name="l00520"></a>00520 
    533. 

  533. <a name="l00521"></a>00521     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    534. 

  534. <a name="l00522"></a>00522     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    535. 

  535. <a name="l00523"></a>00523     T = pSrc[i0];
    536. 

  536. <a name="l00524"></a>00524     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    537. 

  537. <a name="l00525"></a>00525     S = pSrc[i2];
    538. 

  538. <a name="l00526"></a>00526 
    539. 

  539. <a name="l00527"></a>00527     <span class="comment">/* R = packed((ya + yc), (xa + xc)) */</span>
    540. 

  540. <a name="l00528"></a>00528     R = __QADD16(T, S);
    541. 

  541. <a name="l00529"></a>00529     <span class="comment">/* S = packed((ya - yc), (xa - xc)) */</span>
    542. 

  542. <a name="l00530"></a>00530     S = __QSUB16(T, S);
    543. 

  543. <a name="l00531"></a>00531 
    544. 

  544. <a name="l00532"></a>00532     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    545. 

  545. <a name="l00533"></a>00533     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    546. 

  546. <a name="l00534"></a>00534     T = pSrc[i1];
    547. 

  547. <a name="l00535"></a>00535     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    548. 

  548. <a name="l00536"></a>00536     U = pSrc[i3];
    549. 

  549. <a name="l00537"></a>00537 
    550. 

  550. <a name="l00538"></a>00538     <span class="comment">/* T = packed((yb + yd), (xb + xd)) */</span>
    551. 

  551. <a name="l00539"></a>00539     T = __QADD16(T, U);
    552. 

  552. <a name="l00540"></a>00540 
    553. 

  553. <a name="l00541"></a>00541     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    554. 

  554. <a name="l00542"></a>00542     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    555. 

  555. <a name="l00543"></a>00543     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    556. 

  556. <a name="l00544"></a>00544     pSrc[i0] = __SHADD16(R, T);
    557. 

  557. <a name="l00545"></a>00545 
    558. 

  558. <a name="l00546"></a>00546     <span class="comment">/* R = packed((ya + yc) - (yb + yd), (xa + xc) - (xb + xd)) */</span>
    559. 

  559. <a name="l00547"></a>00547     R = __SHSUB16(R, T);
    560. 

  560. <a name="l00548"></a>00548 
    561. 

  561. <a name="l00549"></a>00549     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    562. 

  562. <a name="l00550"></a>00550     T = pSrc[i1];
    563. 

  563. <a name="l00551"></a>00551 
    564. 

  564. <a name="l00552"></a>00552     <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    565. 

  565. <a name="l00553"></a>00553     <span class="comment">/* xc&#39; = (xa-xb+xc-xd) */</span>
    566. 

  566. <a name="l00554"></a>00554     <span class="comment">/* yc&#39; = (ya-yb+yc-yd) */</span>
    567. 

  567. <a name="l00555"></a>00555     pSrc[i1] = R;
    568. 

  568. <a name="l00556"></a>00556 
    569. 

  569. <a name="l00557"></a>00557     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    570. 

  570. <a name="l00558"></a>00558     U = pSrc[i3];
    571. 

  571. <a name="l00559"></a>00559     <span class="comment">/* T = packed( (yb - yd), (xb - xd))  */</span>
    572. 

  572. <a name="l00560"></a>00560     T = __QSUB16(T, U);
    573. 

  573. <a name="l00561"></a>00561 
    574. 

  574. <a name="l00562"></a>00562 
    575. 

  575. <a name="l00563"></a>00563 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    576. 

  576. <a name="l00564"></a>00564 <span class="preprocessor"></span>
    577. 

  577. <a name="l00565"></a>00565     <span class="comment">/*  writing the butterfly processed i0 + fftLen/2 sample */</span>
    578. 

  578. <a name="l00566"></a>00566     <span class="comment">/* xb&#39; = (xa+yb-xc-yd) */</span>
    579. 

  579. <a name="l00567"></a>00567     <span class="comment">/* yb&#39; = (ya-xb-yc+xd) */</span>
    580. 

  580. <a name="l00568"></a>00568     pSrc[i2] = __SHSAX(S, T);
    581. 

  581. <a name="l00569"></a>00569 
    582. 

  582. <a name="l00570"></a>00570     <span class="comment">/*  writing the butterfly processed i0 + 3fftLen/4 sample */</span>
    583. 

  583. <a name="l00571"></a>00571     <span class="comment">/* xd&#39; = (xa-yb-xc+yd) */</span>
    584. 

  584. <a name="l00572"></a>00572     <span class="comment">/* yd&#39; = (ya+xb-yc-xd) */</span>
    585. 

  585. <a name="l00573"></a>00573     pSrc[i3] = __SHASX(S, T);
    586. 

  586. <a name="l00574"></a>00574 
    587. 

  587. <a name="l00575"></a>00575 <span class="preprocessor">#else</span>
    588. 

  588. <a name="l00576"></a>00576 <span class="preprocessor"></span>
    589. 

  589. <a name="l00577"></a>00577     <span class="comment">/*  writing the butterfly processed i0 + fftLen/2 sample */</span>
    590. 

  590. <a name="l00578"></a>00578     <span class="comment">/* xb&#39; = (xa+yb-xc-yd) */</span>
    591. 

  591. <a name="l00579"></a>00579     <span class="comment">/* yb&#39; = (ya-xb-yc+xd) */</span>
    592. 

  592. <a name="l00580"></a>00580     pSrc[i2] = __SHASX(S, T);
    593. 

  593. <a name="l00581"></a>00581 
    594. 

  594. <a name="l00582"></a>00582     <span class="comment">/*  writing the butterfly processed i0 + 3fftLen/4 sample */</span>
    595. 

  595. <a name="l00583"></a>00583     <span class="comment">/* xd&#39; = (xa-yb-xc+yd) */</span>
    596. 

  596. <a name="l00584"></a>00584     <span class="comment">/* yd&#39; = (ya+xb-yc-xd) */</span>
    597. 

  597. <a name="l00585"></a>00585     pSrc[i3] = __SHSAX(S, T);
    598. 

  598. <a name="l00586"></a>00586 
    599. 

  599. <a name="l00587"></a>00587 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    600. 

  600. <a name="l00588"></a>00588 
    601. 

  601. <a name="l00589"></a>00589   }
    602. 

  602. <a name="l00590"></a>00590 
    603. 

  603. <a name="l00591"></a>00591   <span class="comment">/* end of last stage process */</span>
    604. 

  604. <a name="l00592"></a>00592 
    605. 

  605. <a name="l00593"></a>00593   <span class="comment">/* output is in 11.5(q5) format for the 1024 point */</span>
    606. 

  606. <a name="l00594"></a>00594   <span class="comment">/* output is in 9.7(q7) format for the 256 point   */</span>
    607. 

  607. <a name="l00595"></a>00595   <span class="comment">/* output is in 7.9(q9) format for the 64 point  */</span>
    608. 

  608. <a name="l00596"></a>00596   <span class="comment">/* output is in 5.11(q11) format for the 16 point  */</span>
    609. 

  609. <a name="l00597"></a>00597 
    610. 

  610. <a name="l00598"></a>00598 
    611. 

  611. <a name="l00599"></a>00599 <span class="preprocessor">#else</span>
    612. 

  612. <a name="l00600"></a>00600 <span class="preprocessor"></span>
    613. 

  613. <a name="l00601"></a>00601   <span class="comment">/* Run the below code for Cortex-M0 */</span>
    614. 

  614. <a name="l00602"></a>00602 
    615. 

  615. <a name="l00603"></a>00603   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> R0, R1, S0, S1, T0, T1, U0, U1;
    616. 

  616. <a name="l00604"></a>00604   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> Co1, Si1, Co2, Si2, Co3, Si3, out1, out2;
    617. 

  617. <a name="l00605"></a>00605   uint32_t n1, n2, ic, i0, i1, i2, i3, j, k;
    618. 

  618. <a name="l00606"></a>00606 
    619. 

  619. <a name="l00607"></a>00607   <span class="comment">/* Total process is divided into three stages */</span>
    620. 

  620. <a name="l00608"></a>00608 
    621. 

  621. <a name="l00609"></a>00609   <span class="comment">/* process first stage, middle stages, &amp; last stage */</span>
    622. 

  622. <a name="l00610"></a>00610 
    623. 

  623. <a name="l00611"></a>00611   <span class="comment">/*  Initializations for the first stage */</span>
    624. 

  624. <a name="l00612"></a>00612   n2 = fftLen;
    625. 

  625. <a name="l00613"></a>00613   n1 = n2;
    626. 

  626. <a name="l00614"></a>00614 
    627. 

  627. <a name="l00615"></a>00615   <span class="comment">/* n2 = fftLen/4 */</span>
    628. 

  628. <a name="l00616"></a>00616   n2 &gt;&gt;= 2u;
    629. 

  629. <a name="l00617"></a>00617 
    630. 

  630. <a name="l00618"></a>00618   <span class="comment">/* Index for twiddle coefficient */</span>
    631. 

  631. <a name="l00619"></a>00619   ic = 0u;
    632. 

  632. <a name="l00620"></a>00620 
    633. 

  633. <a name="l00621"></a>00621   <span class="comment">/* Index for input read and output write */</span>
    634. 

  634. <a name="l00622"></a>00622   i0 = 0u;
    635. 

  635. <a name="l00623"></a>00623   j = n2;
    636. 

  636. <a name="l00624"></a>00624 
    637. 

  637. <a name="l00625"></a>00625   <span class="comment">/* Input is in 1.15(q15) format */</span>
    638. 

  638. <a name="l00626"></a>00626 
    639. 

  639. <a name="l00627"></a>00627   <span class="comment">/*  start of first stage process */</span>
    640. 

  640. <a name="l00628"></a>00628   <span class="keywordflow">do</span>
    641. 

  641. <a name="l00629"></a>00629   {
    642. 

  642. <a name="l00630"></a>00630     <span class="comment">/*  Butterfly implementation */</span>
    643. 

  643. <a name="l00631"></a>00631 
    644. 

  644. <a name="l00632"></a>00632     <span class="comment">/*  index calculation for the input as, */</span>
    645. 

  645. <a name="l00633"></a>00633     <span class="comment">/*  pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */</span>
    646. 

  646. <a name="l00634"></a>00634     i1 = i0 + n2;
    647. 

  647. <a name="l00635"></a>00635     i2 = i1 + n2;
    648. 

  648. <a name="l00636"></a>00636     i3 = i2 + n2;
    649. 

  649. <a name="l00637"></a>00637 
    650. 

  650. <a name="l00638"></a>00638     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    651. 

  651. <a name="l00639"></a>00639 
    652. 

  652. <a name="l00640"></a>00640     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    653. 

  653. <a name="l00641"></a>00641     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    654. 

  654. <a name="l00642"></a>00642     T0 = pSrc16[i0 * 2u] &gt;&gt; 2u;
    655. 

  655. <a name="l00643"></a>00643     T1 = pSrc16[(i0 * 2u) + 1u] &gt;&gt; 2u;
    656. 

  656. <a name="l00644"></a>00644 
    657. 

  657. <a name="l00645"></a>00645     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    658. 

  658. <a name="l00646"></a>00646     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    659. 

  659. <a name="l00647"></a>00647     S0 = pSrc16[i2 * 2u] &gt;&gt; 2u;
    660. 

  660. <a name="l00648"></a>00648     S1 = pSrc16[(i2 * 2u) + 1u] &gt;&gt; 2u;
    661. 

  661. <a name="l00649"></a>00649 
    662. 

  662. <a name="l00650"></a>00650     <span class="comment">/* R0 = (ya + yc) */</span>
    663. 

  663. <a name="l00651"></a>00651     R0 = __SSAT(T0 + S0, 16u);
    664. 

  664. <a name="l00652"></a>00652     <span class="comment">/* R1 = (xa + xc) */</span>
    665. 

  665. <a name="l00653"></a>00653     R1 = __SSAT(T1 + S1, 16u);
    666. 

  666. <a name="l00654"></a>00654 
    667. 

  667. <a name="l00655"></a>00655     <span class="comment">/* S0 = (ya - yc) */</span>
    668. 

  668. <a name="l00656"></a>00656     S0 = __SSAT(T0 - S0, 16);
    669. 

  669. <a name="l00657"></a>00657     <span class="comment">/* S1 = (xa - xc) */</span>
    670. 

  670. <a name="l00658"></a>00658     S1 = __SSAT(T1 - S1, 16);
    671. 

  671. <a name="l00659"></a>00659 
    672. 

  672. <a name="l00660"></a>00660     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    673. 

  673. <a name="l00661"></a>00661     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    674. 

  674. <a name="l00662"></a>00662     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    675. 

  675. <a name="l00663"></a>00663     T0 = pSrc16[i1 * 2u] &gt;&gt; 2u;
    676. 

  676. <a name="l00664"></a>00664     T1 = pSrc16[(i1 * 2u) + 1u] &gt;&gt; 2u;
    677. 

  677. <a name="l00665"></a>00665 
    678. 

  678. <a name="l00666"></a>00666     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    679. 

  679. <a name="l00667"></a>00667     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    680. 

  680. <a name="l00668"></a>00668     U0 = pSrc16[i3 * 2u] &gt;&gt; 2u;
    681. 

  681. <a name="l00669"></a>00669     U1 = pSrc16[(i3 * 2u) + 1] &gt;&gt; 2u;
    682. 

  682. <a name="l00670"></a>00670 
    683. 

  683. <a name="l00671"></a>00671     <span class="comment">/* T0 = (yb + yd) */</span>
    684. 

  684. <a name="l00672"></a>00672     T0 = __SSAT(T0 + U0, 16u);
    685. 

  685. <a name="l00673"></a>00673     <span class="comment">/* T1 = (xb + xd) */</span>
    686. 

  686. <a name="l00674"></a>00674     T1 = __SSAT(T1 + U1, 16u);
    687. 

  687. <a name="l00675"></a>00675 
    688. 

  688. <a name="l00676"></a>00676     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    689. 

  689. <a name="l00677"></a>00677     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    690. 

  690. <a name="l00678"></a>00678     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    691. 

  691. <a name="l00679"></a>00679     pSrc16[i0 * 2u] = (R0 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    692. 

  692. <a name="l00680"></a>00680     pSrc16[(i0 * 2u) + 1u] = (R1 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    693. 

  693. <a name="l00681"></a>00681 
    694. 

  694. <a name="l00682"></a>00682     <span class="comment">/* R0 = (ya + yc) - (yb + yd) */</span>
    695. 

  695. <a name="l00683"></a>00683     <span class="comment">/* R1 = (xa + xc) - (xb + xd) */</span>
    696. 

  696. <a name="l00684"></a>00684     R0 = __SSAT(R0 - T0, 16u);
    697. 

  697. <a name="l00685"></a>00685     R1 = __SSAT(R1 - T1, 16u);
    698. 

  698. <a name="l00686"></a>00686 
    699. 

  699. <a name="l00687"></a>00687     <span class="comment">/* co2 &amp; si2 are read from Coefficient pointer */</span>
    700. 

  700. <a name="l00688"></a>00688     Co2 = pCoef16[2u * ic * 2u];
    701. 

  701. <a name="l00689"></a>00689     Si2 = pCoef16[(2u * ic * 2u) + 1];
    702. 

  702. <a name="l00690"></a>00690 
    703. 

  703. <a name="l00691"></a>00691     <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */</span>
    704. 

  704. <a name="l00692"></a>00692     out1 = (short) ((Co2 * R0 + Si2 * R1) &gt;&gt; 16u);
    705. 

  705. <a name="l00693"></a>00693     <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    706. 

  706. <a name="l00694"></a>00694     out2 = (short) ((-Si2 * R0 + Co2 * R1) &gt;&gt; 16u);
    707. 

  707. <a name="l00695"></a>00695 
    708. 

  708. <a name="l00696"></a>00696     <span class="comment">/*  Reading i0+fftLen/4 */</span>
    709. 

  709. <a name="l00697"></a>00697     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    710. 

  710. <a name="l00698"></a>00698     <span class="comment">/* T0 = yb, T1 =  xb */</span>
    711. 

  711. <a name="l00699"></a>00699     T0 = pSrc16[i1 * 2u] &gt;&gt; 2;
    712. 

  712. <a name="l00700"></a>00700     T1 = pSrc16[(i1 * 2u) + 1] &gt;&gt; 2;
    713. 

  713. <a name="l00701"></a>00701 
    714. 

  714. <a name="l00702"></a>00702     <span class="comment">/* writing the butterfly processed i0 + fftLen/4 sample */</span>
    715. 

  715. <a name="l00703"></a>00703     <span class="comment">/* writing output(xc&#39;, yc&#39;) in little endian format */</span>
    716. 

  716. <a name="l00704"></a>00704     pSrc16[i1 * 2u] = out1;
    717. 

  717. <a name="l00705"></a>00705     pSrc16[(i1 * 2u) + 1] = out2;
    718. 

  718. <a name="l00706"></a>00706 
    719. 

  719. <a name="l00707"></a>00707     <span class="comment">/*  Butterfly calculations */</span>
    720. 

  720. <a name="l00708"></a>00708     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    721. 

  721. <a name="l00709"></a>00709     <span class="comment">/* U0 = yd, U1 = xd */</span>
    722. 

  722. <a name="l00710"></a>00710     U0 = pSrc16[i3 * 2u] &gt;&gt; 2;
    723. 

  723. <a name="l00711"></a>00711     U1 = pSrc16[(i3 * 2u) + 1] &gt;&gt; 2;
    724. 

  724. <a name="l00712"></a>00712     <span class="comment">/* T0 = yb-yd */</span>
    725. 

  725. <a name="l00713"></a>00713     T0 = __SSAT(T0 - U0, 16);
    726. 

  726. <a name="l00714"></a>00714     <span class="comment">/* T1 = xb-xd */</span>
    727. 

  727. <a name="l00715"></a>00715     T1 = __SSAT(T1 - U1, 16);
    728. 

  728. <a name="l00716"></a>00716 
    729. 

  729. <a name="l00717"></a>00717     <span class="comment">/* R1 = (ya-yc) + (xb- xd),  R0 = (xa-xc) - (yb-yd)) */</span>
    730. 

  730. <a name="l00718"></a>00718     R0 = (short) __SSAT((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) (S0 - T1), 16);
    731. 

  731. <a name="l00719"></a>00719     R1 = (short) __SSAT((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) (S1 + T0), 16);
    732. 

  732. <a name="l00720"></a>00720 
    733. 

  733. <a name="l00721"></a>00721     <span class="comment">/* S1 = (ya-yc) - (xb- xd), S0 = (xa-xc) + (yb-yd)) */</span>
    734. 

  734. <a name="l00722"></a>00722     S0 = (short) __SSAT(((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) S0 + T1), 16u);
    735. 

  735. <a name="l00723"></a>00723     S1 = (short) __SSAT(((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) S1 - T0), 16u);
    736. 

  736. <a name="l00724"></a>00724 
    737. 

  737. <a name="l00725"></a>00725     <span class="comment">/* co1 &amp; si1 are read from Coefficient pointer */</span>
    738. 

  738. <a name="l00726"></a>00726     Co1 = pCoef16[ic * 2u];
    739. 

  739. <a name="l00727"></a>00727     Si1 = pCoef16[(ic * 2u) + 1];
    740. 

  740. <a name="l00728"></a>00728     <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    741. 

  741. <a name="l00729"></a>00729     <span class="comment">/* xb&#39; = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */</span>
    742. 

  742. <a name="l00730"></a>00730     out1 = (short) ((Si1 * S1 + Co1 * S0) &gt;&gt; 16);
    743. 

  743. <a name="l00731"></a>00731     <span class="comment">/* yb&#39; = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */</span>
    744. 

  744. <a name="l00732"></a>00732     out2 = (short) ((-Si1 * S0 + Co1 * S1) &gt;&gt; 16);
    745. 

  745. <a name="l00733"></a>00733 
    746. 

  746. <a name="l00734"></a>00734     <span class="comment">/* writing output(xb&#39;, yb&#39;) in little endian format */</span>
    747. 

  747. <a name="l00735"></a>00735     pSrc16[i2 * 2u] = out1;
    748. 

  748. <a name="l00736"></a>00736     pSrc16[(i2 * 2u) + 1] = out2;
    749. 

  749. <a name="l00737"></a>00737 
    750. 

  750. <a name="l00738"></a>00738     <span class="comment">/* Co3 &amp; si3 are read from Coefficient pointer */</span>
    751. 

  751. <a name="l00739"></a>00739     Co3 = pCoef16[3u * (ic * 2u)];
    752. 

  752. <a name="l00740"></a>00740     Si3 = pCoef16[(3u * (ic * 2u)) + 1];
    753. 

  753. <a name="l00741"></a>00741     <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    754. 

  754. <a name="l00742"></a>00742     <span class="comment">/* xd&#39; = (xa-yb-xc+yd)* Co3 + (ya+xb-yc-xd)* (si3) */</span>
    755. 

  755. <a name="l00743"></a>00743     out1 = (short) ((Si3 * R1 + Co3 * R0) &gt;&gt; 16u);
    756. 

  756. <a name="l00744"></a>00744     <span class="comment">/* yd&#39; = (ya+xb-yc-xd)* Co3 - (xa-yb-xc+yd)* (si3) */</span>
    757. 

  757. <a name="l00745"></a>00745     out2 = (short) ((-Si3 * R0 + Co3 * R1) &gt;&gt; 16u);
    758. 

  758. <a name="l00746"></a>00746     <span class="comment">/* writing output(xd&#39;, yd&#39;) in little endian format */</span>
    759. 

  759. <a name="l00747"></a>00747     pSrc16[i3 * 2u] = out1;
    760. 

  760. <a name="l00748"></a>00748     pSrc16[(i3 * 2u) + 1] = out2;
    761. 

  761. <a name="l00749"></a>00749 
    762. 

  762. <a name="l00750"></a>00750     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    763. 

  763. <a name="l00751"></a>00751     ic = ic + twidCoefModifier;
    764. 

  764. <a name="l00752"></a>00752 
    765. 

  765. <a name="l00753"></a>00753     <span class="comment">/*  Updating input index */</span>
    766. 

  766. <a name="l00754"></a>00754     i0 = i0 + 1u;
    767. 

  767. <a name="l00755"></a>00755 
    768. 

  768. <a name="l00756"></a>00756   } <span class="keywordflow">while</span>(--j);
    769. 

  769. <a name="l00757"></a>00757   <span class="comment">/* data is in 4.11(q11) format */</span>
    770. 

  770. <a name="l00758"></a>00758 
    771. 

  771. <a name="l00759"></a>00759   <span class="comment">/* end of first stage process */</span>
    772. 

  772. <a name="l00760"></a>00760 
    773. 

  773. <a name="l00761"></a>00761 
    774. 

  774. <a name="l00762"></a>00762   <span class="comment">/* start of middle stage process */</span>
    775. 

  775. <a name="l00763"></a>00763 
    776. 

  776. <a name="l00764"></a>00764   <span class="comment">/*  Twiddle coefficients index modifier */</span>
    777. 

  777. <a name="l00765"></a>00765   twidCoefModifier &lt;&lt;= 2u;
    778. 

  778. <a name="l00766"></a>00766 
    779. 

  779. <a name="l00767"></a>00767   <span class="comment">/*  Calculation of Middle stage */</span>
    780. 

  780. <a name="l00768"></a>00768   <span class="keywordflow">for</span> (k = fftLen / 4u; k &gt; 4u; k &gt;&gt;= 2u)
    781. 

  781. <a name="l00769"></a>00769   {
    782. 

  782. <a name="l00770"></a>00770     <span class="comment">/*  Initializations for the middle stage */</span>
    783. 

  783. <a name="l00771"></a>00771     n1 = n2;
    784. 

  784. <a name="l00772"></a>00772     n2 &gt;&gt;= 2u;
    785. 

  785. <a name="l00773"></a>00773     ic = 0u;
    786. 

  786. <a name="l00774"></a>00774 
    787. 

  787. <a name="l00775"></a>00775     <span class="keywordflow">for</span> (j = 0u; j &lt;= (n2 - 1u); j++)
    788. 

  788. <a name="l00776"></a>00776     {
    789. 

  789. <a name="l00777"></a>00777       <span class="comment">/*  index calculation for the coefficients */</span>
    790. 

  790. <a name="l00778"></a>00778       Co1 = pCoef16[ic * 2u];
    791. 

  791. <a name="l00779"></a>00779       Si1 = pCoef16[(ic * 2u) + 1u];
    792. 

  792. <a name="l00780"></a>00780       Co2 = pCoef16[2u * (ic * 2u)];
    793. 

  793. <a name="l00781"></a>00781       Si2 = pCoef16[(2u * (ic * 2u)) + 1u];
    794. 

  794. <a name="l00782"></a>00782       Co3 = pCoef16[3u * (ic * 2u)];
    795. 

  795. <a name="l00783"></a>00783       Si3 = pCoef16[(3u * (ic * 2u)) + 1u];
    796. 

  796. <a name="l00784"></a>00784 
    797. 

  797. <a name="l00785"></a>00785       <span class="comment">/*  Twiddle coefficients index modifier */</span>
    798. 

  798. <a name="l00786"></a>00786       ic = ic + twidCoefModifier;
    799. 

  799. <a name="l00787"></a>00787 
    800. 

  800. <a name="l00788"></a>00788       <span class="comment">/*  Butterfly implementation */</span>
    801. 

  801. <a name="l00789"></a>00789       <span class="keywordflow">for</span> (i0 = j; i0 &lt; fftLen; i0 += n1)
    802. 

  802. <a name="l00790"></a>00790       {
    803. 

  803. <a name="l00791"></a>00791         <span class="comment">/*  index calculation for the input as, */</span>
    804. 

  804. <a name="l00792"></a>00792         <span class="comment">/*  pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */</span>
    805. 

  805. <a name="l00793"></a>00793         i1 = i0 + n2;
    806. 

  806. <a name="l00794"></a>00794         i2 = i1 + n2;
    807. 

  807. <a name="l00795"></a>00795         i3 = i2 + n2;
    808. 

  808. <a name="l00796"></a>00796 
    809. 

  809. <a name="l00797"></a>00797         <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    810. 

  810. <a name="l00798"></a>00798         <span class="comment">/* Read ya (real), xa(imag) input */</span>
    811. 

  811. <a name="l00799"></a>00799         T0 = pSrc16[i0 * 2u];
    812. 

  812. <a name="l00800"></a>00800         T1 = pSrc16[(i0 * 2u) + 1u];
    813. 

  813. <a name="l00801"></a>00801 
    814. 

  814. <a name="l00802"></a>00802         <span class="comment">/* Read yc (real), xc(imag) input */</span>
    815. 

  815. <a name="l00803"></a>00803         S0 = pSrc16[i2 * 2u];
    816. 

  816. <a name="l00804"></a>00804         S1 = pSrc16[(i2 * 2u) + 1u];
    817. 

  817. <a name="l00805"></a>00805 
    818. 

  818. <a name="l00806"></a>00806         <span class="comment">/* R0 = (ya + yc), R1 = (xa + xc) */</span>
    819. 

  819. <a name="l00807"></a>00807         R0 = __SSAT(T0 + S0, 16);
    820. 

  820. <a name="l00808"></a>00808         R1 = __SSAT(T1 + S1, 16);
    821. 

  821. <a name="l00809"></a>00809 
    822. 

  822. <a name="l00810"></a>00810         <span class="comment">/* S0 = (ya - yc), S1 =(xa - xc) */</span>
    823. 

  823. <a name="l00811"></a>00811         S0 = __SSAT(T0 - S0, 16);
    824. 

  824. <a name="l00812"></a>00812         S1 = __SSAT(T1 - S1, 16);
    825. 

  825. <a name="l00813"></a>00813 
    826. 

  826. <a name="l00814"></a>00814         <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    827. 

  827. <a name="l00815"></a>00815         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    828. 

  828. <a name="l00816"></a>00816         T0 = pSrc16[i1 * 2u];
    829. 

  829. <a name="l00817"></a>00817         T1 = pSrc16[(i1 * 2u) + 1u];
    830. 

  830. <a name="l00818"></a>00818 
    831. 

  831. <a name="l00819"></a>00819         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    832. 

  832. <a name="l00820"></a>00820         U0 = pSrc16[i3 * 2u];
    833. 

  833. <a name="l00821"></a>00821         U1 = pSrc16[(i3 * 2u) + 1u];
    834. 

  834. <a name="l00822"></a>00822 
    835. 

  835. <a name="l00823"></a>00823 
    836. 

  836. <a name="l00824"></a>00824         <span class="comment">/* T0 = (yb + yd), T1 = (xb + xd) */</span>
    837. 

  837. <a name="l00825"></a>00825         T0 = __SSAT(T0 + U0, 16);
    838. 

  838. <a name="l00826"></a>00826         T1 = __SSAT(T1 + U1, 16);
    839. 

  839. <a name="l00827"></a>00827 
    840. 

  840. <a name="l00828"></a>00828         <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    841. 

  841. <a name="l00829"></a>00829 
    842. 

  842. <a name="l00830"></a>00830         <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    843. 

  843. <a name="l00831"></a>00831         <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    844. 

  844. <a name="l00832"></a>00832         out1 = ((R0 &gt;&gt; 1u) + (T0 &gt;&gt; 1u)) &gt;&gt; 1u;
    845. 

  845. <a name="l00833"></a>00833         out2 = ((R1 &gt;&gt; 1u) + (T1 &gt;&gt; 1u)) &gt;&gt; 1u;
    846. 

  846. <a name="l00834"></a>00834 
    847. 

  847. <a name="l00835"></a>00835         pSrc16[i0 * 2u] = out1;
    848. 

  848. <a name="l00836"></a>00836         pSrc16[(2u * i0) + 1u] = out2;
    849. 

  849. <a name="l00837"></a>00837 
    850. 

  850. <a name="l00838"></a>00838         <span class="comment">/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */</span>
    851. 

  851. <a name="l00839"></a>00839         R0 = (R0 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    852. 

  852. <a name="l00840"></a>00840         R1 = (R1 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    853. 

  853. <a name="l00841"></a>00841 
    854. 

  854. <a name="l00842"></a>00842         <span class="comment">/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */</span>
    855. 

  855. <a name="l00843"></a>00843         out1 = (short) ((Co2 * R0 + Si2 * R1) &gt;&gt; 16u);
    856. 

  856. <a name="l00844"></a>00844 
    857. 

  857. <a name="l00845"></a>00845         <span class="comment">/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    858. 

  858. <a name="l00846"></a>00846         out2 = (short) ((-Si2 * R0 + Co2 * R1) &gt;&gt; 16u);
    859. 

  859. <a name="l00847"></a>00847 
    860. 

  860. <a name="l00848"></a>00848         <span class="comment">/*  Reading i0+3fftLen/4 */</span>
    861. 

  861. <a name="l00849"></a>00849         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    862. 

  862. <a name="l00850"></a>00850         T0 = pSrc16[i1 * 2u];
    863. 

  863. <a name="l00851"></a>00851         T1 = pSrc16[(i1 * 2u) + 1u];
    864. 

  864. <a name="l00852"></a>00852 
    865. 

  865. <a name="l00853"></a>00853         <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    866. 

  866. <a name="l00854"></a>00854         <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */</span>
    867. 

  867. <a name="l00855"></a>00855         <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */</span>
    868. 

  868. <a name="l00856"></a>00856         pSrc16[i1 * 2u] = out1;
    869. 

  869. <a name="l00857"></a>00857         pSrc16[(i1 * 2u) + 1u] = out2;
    870. 

  870. <a name="l00858"></a>00858 
    871. 

  871. <a name="l00859"></a>00859         <span class="comment">/*  Butterfly calculations */</span>
    872. 

  872. <a name="l00860"></a>00860 
    873. 

  873. <a name="l00861"></a>00861         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    874. 

  874. <a name="l00862"></a>00862         U0 = pSrc16[i3 * 2u];
    875. 

  875. <a name="l00863"></a>00863         U1 = pSrc16[(i3 * 2u) + 1u];
    876. 

  876. <a name="l00864"></a>00864 
    877. 

  877. <a name="l00865"></a>00865         <span class="comment">/* T0 = yb-yd, T1 = xb-xd */</span>
    878. 

  878. <a name="l00866"></a>00866         T0 = __SSAT(T0 - U0, 16);
    879. 

  879. <a name="l00867"></a>00867         T1 = __SSAT(T1 - U1, 16);
    880. 

  880. <a name="l00868"></a>00868 
    881. 

  881. <a name="l00869"></a>00869         <span class="comment">/* R0 = (ya-yc) + (xb- xd), R1 = (xa-xc) - (yb-yd)) */</span>
    882. 

  882. <a name="l00870"></a>00870         R0 = (S0 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    883. 

  883. <a name="l00871"></a>00871         R1 = (S1 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    884. 

  884. <a name="l00872"></a>00872 
    885. 

  885. <a name="l00873"></a>00873         <span class="comment">/* S0 = (ya-yc) - (xb- xd), S1 = (xa-xc) + (yb-yd)) */</span>
    886. 

  886. <a name="l00874"></a>00874         S0 = (S0 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    887. 

  887. <a name="l00875"></a>00875         S1 = (S1 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    888. 

  888. <a name="l00876"></a>00876 
    889. 

  889. <a name="l00877"></a>00877         <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    890. 

  890. <a name="l00878"></a>00878         out1 = (short) ((Co1 * S0 + Si1 * S1) &gt;&gt; 16u);
    891. 

  891. <a name="l00879"></a>00879 
    892. 

  892. <a name="l00880"></a>00880         out2 = (short) ((-Si1 * S0 + Co1 * S1) &gt;&gt; 16u);
    893. 

  893. <a name="l00881"></a>00881 
    894. 

  894. <a name="l00882"></a>00882         <span class="comment">/* xb&#39; = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */</span>
    895. 

  895. <a name="l00883"></a>00883         <span class="comment">/* yb&#39; = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */</span>
    896. 

  896. <a name="l00884"></a>00884         pSrc16[i2 * 2u] = out1;
    897. 

  897. <a name="l00885"></a>00885         pSrc16[(i2 * 2u) + 1u] = out2;
    898. 

  898. <a name="l00886"></a>00886 
    899. 

  899. <a name="l00887"></a>00887         <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    900. 

  900. <a name="l00888"></a>00888         out1 = (short) ((Si3 * R1 + Co3 * R0) &gt;&gt; 16u);
    901. 

  901. <a name="l00889"></a>00889 
    902. 

  902. <a name="l00890"></a>00890         out2 = (short) ((-Si3 * R0 + Co3 * R1) &gt;&gt; 16u);
    903. 

  903. <a name="l00891"></a>00891         <span class="comment">/* xd&#39; = (xa-yb-xc+yd)* Co3 + (ya+xb-yc-xd)* (si3) */</span>
    904. 

  904. <a name="l00892"></a>00892         <span class="comment">/* yd&#39; = (ya+xb-yc-xd)* Co3 - (xa-yb-xc+yd)* (si3) */</span>
    905. 

  905. <a name="l00893"></a>00893         pSrc16[i3 * 2u] = out1;
    906. 

  906. <a name="l00894"></a>00894         pSrc16[(i3 * 2u) + 1u] = out2;
    907. 

  907. <a name="l00895"></a>00895       }
    908. 

  908. <a name="l00896"></a>00896     }
    909. 

  909. <a name="l00897"></a>00897     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    910. 

  910. <a name="l00898"></a>00898     twidCoefModifier &lt;&lt;= 2u;
    911. 

  911. <a name="l00899"></a>00899   }
    912. 

  912. <a name="l00900"></a>00900   <span class="comment">/* end of middle stage process */</span>
    913. 

  913. <a name="l00901"></a>00901 
    914. 

  914. <a name="l00902"></a>00902 
    915. 

  915. <a name="l00903"></a>00903   <span class="comment">/* data is in 10.6(q6) format for the 1024 point */</span>
    916. 

  916. <a name="l00904"></a>00904   <span class="comment">/* data is in 8.8(q8) format for the 256 point */</span>
    917. 

  917. <a name="l00905"></a>00905   <span class="comment">/* data is in 6.10(q10) format for the 64 point */</span>
    918. 

  918. <a name="l00906"></a>00906   <span class="comment">/* data is in 4.12(q12) format for the 16 point */</span>
    919. 

  919. <a name="l00907"></a>00907 
    920. 

  920. <a name="l00908"></a>00908   <span class="comment">/*  Initializations for the last stage */</span>
    921. 

  921. <a name="l00909"></a>00909   n1 = n2;
    922. 

  922. <a name="l00910"></a>00910   n2 &gt;&gt;= 2u;
    923. 

  923. <a name="l00911"></a>00911 
    924. 

  924. <a name="l00912"></a>00912   <span class="comment">/* start of last stage process */</span>
    925. 

  925. <a name="l00913"></a>00913 
    926. 

  926. <a name="l00914"></a>00914   <span class="comment">/*  Butterfly implementation */</span>
    927. 

  927. <a name="l00915"></a>00915   <span class="keywordflow">for</span> (i0 = 0u; i0 &lt;= (fftLen - n1); i0 += n1)
    928. 

  928. <a name="l00916"></a>00916   {
    929. 

  929. <a name="l00917"></a>00917     <span class="comment">/*  index calculation for the input as, */</span>
    930. 

  930. <a name="l00918"></a>00918     <span class="comment">/*  pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */</span>
    931. 

  931. <a name="l00919"></a>00919     i1 = i0 + n2;
    932. 

  932. <a name="l00920"></a>00920     i2 = i1 + n2;
    933. 

  933. <a name="l00921"></a>00921     i3 = i2 + n2;
    934. 

  934. <a name="l00922"></a>00922 
    935. 

  935. <a name="l00923"></a>00923     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    936. 

  936. <a name="l00924"></a>00924     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    937. 

  937. <a name="l00925"></a>00925     T0 = pSrc16[i0 * 2u];
    938. 

  938. <a name="l00926"></a>00926     T1 = pSrc16[(i0 * 2u) + 1u];
    939. 

  939. <a name="l00927"></a>00927 
    940. 

  940. <a name="l00928"></a>00928     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    941. 

  941. <a name="l00929"></a>00929     S0 = pSrc16[i2 * 2u];
    942. 

  942. <a name="l00930"></a>00930     S1 = pSrc16[(i2 * 2u) + 1u];
    943. 

  943. <a name="l00931"></a>00931 
    944. 

  944. <a name="l00932"></a>00932     <span class="comment">/* R0 = (ya + yc), R1 = (xa + xc) */</span>
    945. 

  945. <a name="l00933"></a>00933     R0 = __SSAT(T0 + S0, 16u);
    946. 

  946. <a name="l00934"></a>00934     R1 = __SSAT(T1 + S1, 16u);
    947. 

  947. <a name="l00935"></a>00935 
    948. 

  948. <a name="l00936"></a>00936     <span class="comment">/* S0 = (ya - yc), S1 = (xa - xc) */</span>
    949. 

  949. <a name="l00937"></a>00937     S0 = __SSAT(T0 - S0, 16u);
    950. 

  950. <a name="l00938"></a>00938     S1 = __SSAT(T1 - S1, 16u);
    951. 

  951. <a name="l00939"></a>00939 
    952. 

  952. <a name="l00940"></a>00940     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    953. 

  953. <a name="l00941"></a>00941     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    954. 

  954. <a name="l00942"></a>00942     T0 = pSrc16[i1 * 2u];
    955. 

  955. <a name="l00943"></a>00943     T1 = pSrc16[(i1 * 2u) + 1u];
    956. 

  956. <a name="l00944"></a>00944     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    957. 

  957. <a name="l00945"></a>00945     U0 = pSrc16[i3 * 2u];
    958. 

  958. <a name="l00946"></a>00946     U1 = pSrc16[(i3 * 2u) + 1u];
    959. 

  959. <a name="l00947"></a>00947 
    960. 

  960. <a name="l00948"></a>00948     <span class="comment">/* T0 = (yb + yd), T1 = (xb + xd)) */</span>
    961. 

  961. <a name="l00949"></a>00949     T0 = __SSAT(T0 + U0, 16u);
    962. 

  962. <a name="l00950"></a>00950     T1 = __SSAT(T1 + U1, 16u);
    963. 

  963. <a name="l00951"></a>00951 
    964. 

  964. <a name="l00952"></a>00952     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    965. 

  965. <a name="l00953"></a>00953     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    966. 

  966. <a name="l00954"></a>00954     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    967. 

  967. <a name="l00955"></a>00955     pSrc16[i0 * 2u] = (R0 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    968. 

  968. <a name="l00956"></a>00956     pSrc16[(i0 * 2u) + 1u] = (R1 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    969. 

  969. <a name="l00957"></a>00957 
    970. 

  970. <a name="l00958"></a>00958     <span class="comment">/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */</span>
    971. 

  971. <a name="l00959"></a>00959     R0 = (R0 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    972. 

  972. <a name="l00960"></a>00960     R1 = (R1 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    973. 

  973. <a name="l00961"></a>00961     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    974. 

  974. <a name="l00962"></a>00962     T0 = pSrc16[i1 * 2u];
    975. 

  975. <a name="l00963"></a>00963     T1 = pSrc16[(i1 * 2u) + 1u];
    976. 

  976. <a name="l00964"></a>00964 
    977. 

  977. <a name="l00965"></a>00965     <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    978. 

  978. <a name="l00966"></a>00966     <span class="comment">/* xc&#39; = (xa-xb+xc-xd) */</span>
    979. 

  979. <a name="l00967"></a>00967     <span class="comment">/* yc&#39; = (ya-yb+yc-yd) */</span>
    980. 

  980. <a name="l00968"></a>00968     pSrc16[i1 * 2u] = R0;
    981. 

  981. <a name="l00969"></a>00969     pSrc16[(i1 * 2u) + 1u] = R1;
    982. 

  982. <a name="l00970"></a>00970 
    983. 

  983. <a name="l00971"></a>00971     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    984. 

  984. <a name="l00972"></a>00972     U0 = pSrc16[i3 * 2u];
    985. 

  985. <a name="l00973"></a>00973     U1 = pSrc16[(i3 * 2u) + 1u];
    986. 

  986. <a name="l00974"></a>00974     <span class="comment">/* T0 = (yb - yd), T1 = (xb - xd)  */</span>
    987. 

  987. <a name="l00975"></a>00975     T0 = __SSAT(T0 - U0, 16u);
    988. 

  988. <a name="l00976"></a>00976     T1 = __SSAT(T1 - U1, 16u);
    989. 

  989. <a name="l00977"></a>00977 
    990. 

  990. <a name="l00978"></a>00978     <span class="comment">/*  writing the butterfly processed i0 + fftLen/2 sample */</span>
    991. 

  991. <a name="l00979"></a>00979     <span class="comment">/* xb&#39; = (xa+yb-xc-yd) */</span>
    992. 

  992. <a name="l00980"></a>00980     <span class="comment">/* yb&#39; = (ya-xb-yc+xd) */</span>
    993. 

  993. <a name="l00981"></a>00981     pSrc16[i2 * 2u] = (S0 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    994. 

  994. <a name="l00982"></a>00982     pSrc16[(i2 * 2u) + 1u] = (S1 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    995. 

  995. <a name="l00983"></a>00983 
    996. 

  996. <a name="l00984"></a>00984     <span class="comment">/*  writing the butterfly processed i0 + 3fftLen/4 sample */</span>
    997. 

  997. <a name="l00985"></a>00985     <span class="comment">/* xd&#39; = (xa-yb-xc+yd) */</span>
    998. 

  998. <a name="l00986"></a>00986     <span class="comment">/* yd&#39; = (ya+xb-yc-xd) */</span>
    999. 

  999. <a name="l00987"></a>00987     pSrc16[i3 * 2u] = (S0 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    1000. 

  1000. <a name="l00988"></a>00988     pSrc16[(i3 * 2u) + 1u] = (S1 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    1001. 

  1001. <a name="l00989"></a>00989 
    1002. 

  1002. <a name="l00990"></a>00990   }
    1003. 

  1003. <a name="l00991"></a>00991 
    1004. 

  1004. <a name="l00992"></a>00992   <span class="comment">/* end of last stage process */</span>
    1005. 

  1005. <a name="l00993"></a>00993 
    1006. 

  1006. <a name="l00994"></a>00994   <span class="comment">/* output is in 11.5(q5) format for the 1024 point */</span>
    1007. 

  1007. <a name="l00995"></a>00995   <span class="comment">/* output is in 9.7(q7) format for the 256 point   */</span>
    1008. 

  1008. <a name="l00996"></a>00996   <span class="comment">/* output is in 7.9(q9) format for the 64 point  */</span>
    1009. 

  1009. <a name="l00997"></a>00997   <span class="comment">/* output is in 5.11(q11) format for the 16 point  */</span>
    1010. 

  1010. <a name="l00998"></a>00998 
    1011. 

  1011. <a name="l00999"></a>00999 <span class="preprocessor">#endif </span><span class="comment">/* #ifndef ARM_MATH_CM0 */</span>
    1012. 

  1012. <a name="l01000"></a>01000 
    1013. 

  1013. <a name="l01001"></a>01001 }
    1014. 

  1014. <a name="l01002"></a>01002 
    1015. 

  1015. <a name="l01003"></a>01003 
    1016. 

  1016. <a name="l01013"></a>01013 <span class="comment">/*   </span>
    1017. 

  1017. <a name="l01014"></a>01014 <span class="comment">* Radix-4 IFFT algorithm used is :   </span>
    1018. 

  1018. <a name="l01015"></a>01015 <span class="comment">*   </span>
    1019. 

  1019. <a name="l01016"></a>01016 <span class="comment">* CIFFT uses same twiddle coefficients as CFFT function   </span>
    1020. 

  1020. <a name="l01017"></a>01017 <span class="comment">*  x[k] = x[n] + (j)k * x[n + fftLen/4] + (-1)k * x[n+fftLen/2] + (-j)k * x[n+3*fftLen/4]   </span>
    1021. 

  1021. <a name="l01018"></a>01018 <span class="comment">*   </span>
    1022. 

  1022. <a name="l01019"></a>01019 <span class="comment">*   </span>
    1023. 

  1023. <a name="l01020"></a>01020 <span class="comment">* IFFT is implemented with following changes in equations from FFT   </span>
    1024. 

  1024. <a name="l01021"></a>01021 <span class="comment">*   </span>
    1025. 

  1025. <a name="l01022"></a>01022 <span class="comment">* Input real and imaginary data:   </span>
    1026. 

  1026. <a name="l01023"></a>01023 <span class="comment">* x(n) = xa + j * ya   </span>
    1027. 

  1027. <a name="l01024"></a>01024 <span class="comment">* x(n+N/4 ) = xb + j * yb   </span>
    1028. 

  1028. <a name="l01025"></a>01025 <span class="comment">* x(n+N/2 ) = xc + j * yc   </span>
    1029. 

  1029. <a name="l01026"></a>01026 <span class="comment">* x(n+3N 4) = xd + j * yd   </span>
    1030. 

  1030. <a name="l01027"></a>01027 <span class="comment">*   </span>
    1031. 

  1031. <a name="l01028"></a>01028 <span class="comment">*   </span>
    1032. 

  1032. <a name="l01029"></a>01029 <span class="comment">* Output real and imaginary data:   </span>
    1033. 

  1033. <a name="l01030"></a>01030 <span class="comment">* x(4r) = xa&#39;+ j * ya&#39;   </span>
    1034. 

  1034. <a name="l01031"></a>01031 <span class="comment">* x(4r+1) = xb&#39;+ j * yb&#39;   </span>
    1035. 

  1035. <a name="l01032"></a>01032 <span class="comment">* x(4r+2) = xc&#39;+ j * yc&#39;   </span>
    1036. 

  1036. <a name="l01033"></a>01033 <span class="comment">* x(4r+3) = xd&#39;+ j * yd&#39;   </span>
    1037. 

  1037. <a name="l01034"></a>01034 <span class="comment">*   </span>
    1038. 

  1038. <a name="l01035"></a>01035 <span class="comment">*   </span>
    1039. 

  1039. <a name="l01036"></a>01036 <span class="comment">* Twiddle factors for radix-4 IFFT:   </span>
    1040. 

  1040. <a name="l01037"></a>01037 <span class="comment">* Wn = co1 + j * (si1)   </span>
    1041. 

  1041. <a name="l01038"></a>01038 <span class="comment">* W2n = co2 + j * (si2)   </span>
    1042. 

  1042. <a name="l01039"></a>01039 <span class="comment">* W3n = co3 + j * (si3)   </span>
    1043. 

  1043. <a name="l01040"></a>01040 <span class="comment">   </span>
    1044. 

  1044. <a name="l01041"></a>01041 <span class="comment">* The real and imaginary output values for the radix-4 butterfly are   </span>
    1045. 

  1045. <a name="l01042"></a>01042 <span class="comment">* xa&#39; = xa + xb + xc + xd   </span>
    1046. 

  1046. <a name="l01043"></a>01043 <span class="comment">* ya&#39; = ya + yb + yc + yd   </span>
    1047. 

  1047. <a name="l01044"></a>01044 <span class="comment">* xb&#39; = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1)   </span>
    1048. 

  1048. <a name="l01045"></a>01045 <span class="comment">* yb&#39; = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1)   </span>
    1049. 

  1049. <a name="l01046"></a>01046 <span class="comment">* xc&#39; = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2)   </span>
    1050. 

  1050. <a name="l01047"></a>01047 <span class="comment">* yc&#39; = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2)   </span>
    1051. 

  1051. <a name="l01048"></a>01048 <span class="comment">* xd&#39; = (xa+yb-xc-yd)* co3 - (ya-xb-yc+xd)* (si3)   </span>
    1052. 

  1052. <a name="l01049"></a>01049 <span class="comment">* yd&#39; = (ya-xb-yc+xd)* co3 + (xa+yb-xc-yd)* (si3)   </span>
    1053. 

  1053. <a name="l01050"></a>01050 <span class="comment">*   </span>
    1054. 

  1054. <a name="l01051"></a>01051 <span class="comment">*/</span>
    1055. 

  1055. <a name="l01052"></a>01052 
    1056. 

  1056. <a name="l01053"></a><a class="code" href="arm__math_8h.html#aad04e8439d17dab5617bf1be268bb391">01053</a> <span class="keywordtype">void</span> <a class="code" href="arm__cfft__radix4__q15_8c.html#aad04e8439d17dab5617bf1be268bb391" title="Core function for the Q15 CIFFT butterfly process.">arm_radix4_butterfly_inverse_q15</a>(
    1057. 

  1057. <a name="l01054"></a>01054   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pSrc16,
    1058. 

  1058. <a name="l01055"></a>01055   uint32_t fftLen,
    1059. 

  1059. <a name="l01056"></a>01056   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pCoef16,
    1060. 

  1060. <a name="l01057"></a>01057   uint32_t twidCoefModifier)
    1061. 

  1061. <a name="l01058"></a>01058 {
    1062. 

  1062. <a name="l01059"></a>01059 
    1063. 

  1063. <a name="l01060"></a>01060 <span class="preprocessor">#ifndef ARM_MATH_CM0</span>
    1064. 

  1064. <a name="l01061"></a>01061 <span class="preprocessor"></span>
    1065. 

  1065. <a name="l01062"></a>01062   <span class="comment">/* Run the below code for Cortex-M4 and Cortex-M3 */</span>
    1066. 

  1066. <a name="l01063"></a>01063 
    1067. 

  1067. <a name="l01064"></a>01064   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> R, S, T, U;
    1068. 

  1068. <a name="l01065"></a>01065   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> C1, C2, C3, out1, out2;
    1069. 

  1069. <a name="l01066"></a>01066   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *pSrc, *pCoeff;
    1070. 

  1070. <a name="l01067"></a>01067   uint32_t n1, n2, ic, i0, i1, i2, i3, j, k;
    1071. 

  1071. <a name="l01068"></a>01068   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> in;
    1072. 

  1072. <a name="l01069"></a>01069 
    1073. 

  1073. <a name="l01070"></a>01070   <span class="comment">/* Total process is divided into three stages */</span>
    1074. 

  1074. <a name="l01071"></a>01071 
    1075. 

  1075. <a name="l01072"></a>01072   <span class="comment">/* process first stage, middle stages, &amp; last stage */</span>
    1076. 

  1076. <a name="l01073"></a>01073 
    1077. 

  1077. <a name="l01074"></a>01074   <span class="comment">/*  pointer initializations for SIMD calculations */</span>
    1078. 

  1078. <a name="l01075"></a>01075   pSrc = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *) pSrc16;
    1079. 

  1079. <a name="l01076"></a>01076   pCoeff = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *) pCoef16;
    1080. 

  1080. <a name="l01077"></a>01077 
    1081. 

  1081. <a name="l01078"></a>01078   <span class="comment">/*  Initializations for the first stage */</span>
    1082. 

  1082. <a name="l01079"></a>01079   n2 = fftLen;
    1083. 

  1083. <a name="l01080"></a>01080   n1 = n2;
    1084. 

  1084. <a name="l01081"></a>01081 
    1085. 

  1085. <a name="l01082"></a>01082   <span class="comment">/* n2 = fftLen/4 */</span>
    1086. 

  1086. <a name="l01083"></a>01083   n2 &gt;&gt;= 2u;
    1087. 

  1087. <a name="l01084"></a>01084 
    1088. 

  1088. <a name="l01085"></a>01085   <span class="comment">/* Index for twiddle coefficient */</span>
    1089. 

  1089. <a name="l01086"></a>01086   ic = 0u;
    1090. 

  1090. <a name="l01087"></a>01087 
    1091. 

  1091. <a name="l01088"></a>01088   <span class="comment">/* Index for input read and output write */</span>
    1092. 

  1092. <a name="l01089"></a>01089   i0 = 0u;
    1093. 

  1093. <a name="l01090"></a>01090 
    1094. 

  1094. <a name="l01091"></a>01091   j = n2;
    1095. 

  1095. <a name="l01092"></a>01092 
    1096. 

  1096. <a name="l01093"></a>01093   <span class="comment">/* Input is in 1.15(q15) format */</span>
    1097. 

  1097. <a name="l01094"></a>01094 
    1098. 

  1098. <a name="l01095"></a>01095   <span class="comment">/*  Start of first stage process */</span>
    1099. 

  1099. <a name="l01096"></a>01096   <span class="keywordflow">do</span>
    1100. 

  1100. <a name="l01097"></a>01097   {
    1101. 

  1101. <a name="l01098"></a>01098     <span class="comment">/*  Butterfly implementation */</span>
    1102. 

  1102. <a name="l01099"></a>01099 
    1103. 

  1103. <a name="l01100"></a>01100     <span class="comment">/*  index calculation for the input as, */</span>
    1104. 

  1104. <a name="l01101"></a>01101     <span class="comment">/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */</span>
    1105. 

  1105. <a name="l01102"></a>01102     i1 = i0 + n2;
    1106. 

  1106. <a name="l01103"></a>01103     i2 = i1 + n2;
    1107. 

  1107. <a name="l01104"></a>01104     i3 = i2 + n2;
    1108. 

  1108. <a name="l01105"></a>01105 
    1109. 

  1109. <a name="l01106"></a>01106     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    1110. 

  1110. <a name="l01107"></a>01107     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    1111. 

  1111. <a name="l01108"></a>01108     T = pSrc[i0];
    1112. 

  1112. <a name="l01109"></a>01109     in = ((int16_t) (T &amp; 0xFFFF)) &gt;&gt; 2;
    1113. 

  1113. <a name="l01110"></a>01110     T = ((T &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    1114. 

  1114. <a name="l01111"></a>01111     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    1115. 

  1115. <a name="l01112"></a>01112     S = pSrc[i2];
    1116. 

  1116. <a name="l01113"></a>01113     in = ((int16_t) (S &amp; 0xFFFF)) &gt;&gt; 2;
    1117. 

  1117. <a name="l01114"></a>01114     S = ((S &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    1118. 

  1118. <a name="l01115"></a>01115 
    1119. 

  1119. <a name="l01116"></a>01116     <span class="comment">/* R = packed((ya + yc), (xa + xc) ) */</span>
    1120. 

  1120. <a name="l01117"></a>01117     R = __QADD16(T, S);
    1121. 

  1121. <a name="l01118"></a>01118     <span class="comment">/* S = packed((ya - yc), (xa - xc) ) */</span>
    1122. 

  1122. <a name="l01119"></a>01119     S = __QSUB16(T, S);
    1123. 

  1123. <a name="l01120"></a>01120 
    1124. 

  1124. <a name="l01121"></a>01121     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    1125. 

  1125. <a name="l01122"></a>01122     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1126. 

  1126. <a name="l01123"></a>01123     T = pSrc[i1];
    1127. 

  1127. <a name="l01124"></a>01124     in = ((int16_t) (T &amp; 0xFFFF)) &gt;&gt; 2;
    1128. 

  1128. <a name="l01125"></a>01125     T = ((T &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    1129. 

  1129. <a name="l01126"></a>01126     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1130. 

  1130. <a name="l01127"></a>01127     U = pSrc[i3];
    1131. 

  1131. <a name="l01128"></a>01128     in = ((int16_t) (U &amp; 0xFFFF)) &gt;&gt; 2;
    1132. 

  1132. <a name="l01129"></a>01129     U = ((U &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    1133. 

  1133. <a name="l01130"></a>01130 
    1134. 

  1134. <a name="l01131"></a>01131     <span class="comment">/* T = packed((yb + yd), (xb + xd) ) */</span>
    1135. 

  1135. <a name="l01132"></a>01132     T = __QADD16(T, U);
    1136. 

  1136. <a name="l01133"></a>01133 
    1137. 

  1137. <a name="l01134"></a>01134     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    1138. 

  1138. <a name="l01135"></a>01135     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    1139. 

  1139. <a name="l01136"></a>01136     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    1140. 

  1140. <a name="l01137"></a>01137     pSrc[i0] = __SHADD16(R, T);
    1141. 

  1141. <a name="l01138"></a>01138 
    1142. 

  1142. <a name="l01139"></a>01139     <span class="comment">/* R = packed((ya + yc) - (yb + yd), (xa + xc)- (xb + xd)) */</span>
    1143. 

  1143. <a name="l01140"></a>01140     R = __QSUB16(R, T);
    1144. 

  1144. <a name="l01141"></a>01141     <span class="comment">/* co2 &amp; si2 are read from SIMD Coefficient pointer */</span>
    1145. 

  1145. <a name="l01142"></a>01142     C2 = pCoeff[2u * ic];
    1146. 

  1146. <a name="l01143"></a>01143 
    1147. 

  1147. <a name="l01144"></a>01144 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1148. 

  1148. <a name="l01145"></a>01145 <span class="preprocessor"></span>
    1149. 

  1149. <a name="l01146"></a>01146     <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) */</span>
    1150. 

  1150. <a name="l01147"></a>01147     out1 = __SMUSD(C2, R) &gt;&gt; 16u;
    1151. 

  1151. <a name="l01148"></a>01148     <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1152. 

  1152. <a name="l01149"></a>01149     out2 = __SMUADX(C2, R);
    1153. 

  1153. <a name="l01150"></a>01150 
    1154. 

  1154. <a name="l01151"></a>01151 <span class="preprocessor">#else</span>
    1155. 

  1155. <a name="l01152"></a>01152 <span class="preprocessor"></span>
    1156. 

  1156. <a name="l01153"></a>01153     <span class="comment">/* xc&#39; = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1157. 

  1157. <a name="l01154"></a>01154     out1 = __SMUADX(C2, R) &gt;&gt; 16u;
    1158. 

  1158. <a name="l01155"></a>01155     <span class="comment">/* yc&#39; = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) */</span>
    1159. 

  1159. <a name="l01156"></a>01156     out2 = __SMUSD(-C2, R);
    1160. 

  1160. <a name="l01157"></a>01157 
    1161. 

  1161. <a name="l01158"></a>01158 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1162. 

  1162. <a name="l01159"></a>01159 
    1163. 

  1163. <a name="l01160"></a>01160     <span class="comment">/*  Reading i0+fftLen/4 */</span>
    1164. 

  1164. <a name="l01161"></a>01161     <span class="comment">/* T = packed(yb, xb) */</span>
    1165. 

  1165. <a name="l01162"></a>01162     T = pSrc[i1];
    1166. 

  1166. <a name="l01163"></a>01163     in = ((int16_t) (T &amp; 0xFFFF)) &gt;&gt; 2;
    1167. 

  1167. <a name="l01164"></a>01164     T = ((T &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    1168. 

  1168. <a name="l01165"></a>01165 
    1169. 

  1169. <a name="l01166"></a>01166     <span class="comment">/* writing the butterfly processed i0 + fftLen/4 sample */</span>
    1170. 

  1170. <a name="l01167"></a>01167     <span class="comment">/* writing output(xc&#39;, yc&#39;) in little endian format */</span>
    1171. 

  1171. <a name="l01168"></a>01168     pSrc[i1] = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    1172. 

  1172. <a name="l01169"></a>01169 
    1173. 

  1173. <a name="l01170"></a>01170     <span class="comment">/*  Butterfly calculations */</span>
    1174. 

  1174. <a name="l01171"></a>01171     <span class="comment">/* U = packed(yd, xd) */</span>
    1175. 

  1175. <a name="l01172"></a>01172     U = pSrc[i3];
    1176. 

  1176. <a name="l01173"></a>01173     in = ((int16_t) (U &amp; 0xFFFF)) &gt;&gt; 2;
    1177. 

  1177. <a name="l01174"></a>01174     U = ((U &gt;&gt; 2) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    1178. 

  1178. <a name="l01175"></a>01175 
    1179. 

  1179. <a name="l01176"></a>01176     <span class="comment">/* T = packed(yb-yd, xb-xd) */</span>
    1180. 

  1180. <a name="l01177"></a>01177     T = __QSUB16(T, U);
    1181. 

  1181. <a name="l01178"></a>01178 
    1182. 

  1182. <a name="l01179"></a>01179 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1183. 

  1183. <a name="l01180"></a>01180 <span class="preprocessor"></span>
    1184. 

  1184. <a name="l01181"></a>01181     <span class="comment">/* R = packed((ya-yc) - (xb- xd) , (xa-xc) + (yb-yd)) */</span>
    1185. 

  1185. <a name="l01182"></a>01182     R = __QSAX(S, T);
    1186. 

  1186. <a name="l01183"></a>01183     <span class="comment">/* S = packed((ya-yc) + (xb- xd),  (xa-xc) - (yb-yd)) */</span>
    1187. 

  1187. <a name="l01184"></a>01184     S = __QASX(S, T);
    1188. 

  1188. <a name="l01185"></a>01185 
    1189. 

  1189. <a name="l01186"></a>01186 <span class="preprocessor">#else</span>
    1190. 

  1190. <a name="l01187"></a>01187 <span class="preprocessor"></span>
    1191. 

  1191. <a name="l01188"></a>01188     <span class="comment">/* R = packed((ya-yc) - (xb- xd) , (xa-xc) + (yb-yd)) */</span>
    1192. 

  1192. <a name="l01189"></a>01189     R = __QASX(S, T);
    1193. 

  1193. <a name="l01190"></a>01190     <span class="comment">/* S = packed((ya-yc) + (xb- xd),  (xa-xc) - (yb-yd)) */</span>
    1194. 

  1194. <a name="l01191"></a>01191     S = __QSAX(S, T);
    1195. 

  1195. <a name="l01192"></a>01192 
    1196. 

  1196. <a name="l01193"></a>01193 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1197. 

  1197. <a name="l01194"></a>01194 
    1198. 

  1198. <a name="l01195"></a>01195     <span class="comment">/* co1 &amp; si1 are read from SIMD Coefficient pointer */</span>
    1199. 

  1199. <a name="l01196"></a>01196     C1 = pCoeff[ic];
    1200. 

  1200. <a name="l01197"></a>01197     <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    1201. 

  1201. <a name="l01198"></a>01198 
    1202. 

  1202. <a name="l01199"></a>01199 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1203. 

  1203. <a name="l01200"></a>01200 <span class="preprocessor"></span>
    1204. 

  1204. <a name="l01201"></a>01201     <span class="comment">/* xb&#39; = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) */</span>
    1205. 

  1205. <a name="l01202"></a>01202     out1 = __SMUSD(C1, S) &gt;&gt; 16u;
    1206. 

  1206. <a name="l01203"></a>01203     <span class="comment">/* yb&#39; = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */</span>
    1207. 

  1207. <a name="l01204"></a>01204     out2 = __SMUADX(C1, S);
    1208. 

  1208. <a name="l01205"></a>01205 
    1209. 

  1209. <a name="l01206"></a>01206 <span class="preprocessor">#else</span>
    1210. 

  1210. <a name="l01207"></a>01207 <span class="preprocessor"></span>
    1211. 

  1211. <a name="l01208"></a>01208     <span class="comment">/* xb&#39; = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */</span>
    1212. 

  1212. <a name="l01209"></a>01209     out1 = __SMUADX(C1, S) &gt;&gt; 16u;
    1213. 

  1213. <a name="l01210"></a>01210     <span class="comment">/* yb&#39; = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) */</span>
    1214. 

  1214. <a name="l01211"></a>01211     out2 = __SMUSD(-C1, S);
    1215. 

  1215. <a name="l01212"></a>01212 
    1216. 

  1216. <a name="l01213"></a>01213 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1217. 

  1217. <a name="l01214"></a>01214 
    1218. 

  1218. <a name="l01215"></a>01215     <span class="comment">/* writing output(xb&#39;, yb&#39;) in little endian format */</span>
    1219. 

  1219. <a name="l01216"></a>01216     pSrc[i2] = ((out2) &amp; 0xFFFF0000) | ((out1) &amp; 0x0000FFFF);
    1220. 

  1220. <a name="l01217"></a>01217 
    1221. 

  1221. <a name="l01218"></a>01218     <span class="comment">/* co3 &amp; si3 are read from SIMD Coefficient pointer */</span>
    1222. 

  1222. <a name="l01219"></a>01219     C3 = pCoeff[3u * ic];
    1223. 

  1223. <a name="l01220"></a>01220     <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    1224. 

  1224. <a name="l01221"></a>01221 
    1225. 

  1225. <a name="l01222"></a>01222 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1226. 

  1226. <a name="l01223"></a>01223 <span class="preprocessor"></span>
    1227. 

  1227. <a name="l01224"></a>01224     <span class="comment">/* xd&#39; = (xa+yb-xc-yd)* co3 - (ya-xb-yc+xd)* (si3) */</span>
    1228. 

  1228. <a name="l01225"></a>01225     out1 = __SMUSD(C3, R) &gt;&gt; 16u;
    1229. 

  1229. <a name="l01226"></a>01226     <span class="comment">/* yd&#39; = (ya-xb-yc+xd)* co3 + (xa+yb-xc-yd)* (si3) */</span>
    1230. 

  1230. <a name="l01227"></a>01227     out2 = __SMUADX(C3, R);
    1231. 

  1231. <a name="l01228"></a>01228 
    1232. 

  1232. <a name="l01229"></a>01229 <span class="preprocessor">#else</span>
    1233. 

  1233. <a name="l01230"></a>01230 <span class="preprocessor"></span>
    1234. 

  1234. <a name="l01231"></a>01231     <span class="comment">/* xd&#39; = (ya-xb-yc+xd)* co3 + (xa+yb-xc-yd)* (si3) */</span>
    1235. 

  1235. <a name="l01232"></a>01232     out1 = __SMUADX(C3, R) &gt;&gt; 16u;
    1236. 

  1236. <a name="l01233"></a>01233     <span class="comment">/* yd&#39; = (xa+yb-xc-yd)* co3 - (ya-xb-yc+xd)* (si3) */</span>
    1237. 

  1237. <a name="l01234"></a>01234     out2 = __SMUSD(-C3, R);
    1238. 

  1238. <a name="l01235"></a>01235 
    1239. 

  1239. <a name="l01236"></a>01236 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1240. 

  1240. <a name="l01237"></a>01237 
    1241. 

  1241. <a name="l01238"></a>01238     <span class="comment">/* writing output(xd&#39;, yd&#39;) in little endian format */</span>
    1242. 

  1242. <a name="l01239"></a>01239     pSrc[i3] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    1243. 

  1243. <a name="l01240"></a>01240 
    1244. 

  1244. <a name="l01241"></a>01241     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1245. 

  1245. <a name="l01242"></a>01242     ic = ic + twidCoefModifier;
    1246. 

  1246. <a name="l01243"></a>01243 
    1247. 

  1247. <a name="l01244"></a>01244     <span class="comment">/*  Updating input index */</span>
    1248. 

  1248. <a name="l01245"></a>01245     i0 = i0 + 1u;
    1249. 

  1249. <a name="l01246"></a>01246 
    1250. 

  1250. <a name="l01247"></a>01247   } <span class="keywordflow">while</span>(--j);
    1251. 

  1251. <a name="l01248"></a>01248 
    1252. 

  1252. <a name="l01249"></a>01249   <span class="comment">/*  End of first stage process */</span>
    1253. 

  1253. <a name="l01250"></a>01250 
    1254. 

  1254. <a name="l01251"></a>01251   <span class="comment">/* data is in 4.11(q11) format */</span>
    1255. 

  1255. <a name="l01252"></a>01252 
    1256. 

  1256. <a name="l01253"></a>01253 
    1257. 

  1257. <a name="l01254"></a>01254   <span class="comment">/*  Start of Middle stage process */</span>
    1258. 

  1258. <a name="l01255"></a>01255 
    1259. 

  1259. <a name="l01256"></a>01256   <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1260. 

  1260. <a name="l01257"></a>01257   twidCoefModifier &lt;&lt;= 2u;
    1261. 

  1261. <a name="l01258"></a>01258 
    1262. 

  1262. <a name="l01259"></a>01259   <span class="comment">/*  Calculation of Middle stage */</span>
    1263. 

  1263. <a name="l01260"></a>01260   <span class="keywordflow">for</span> (k = fftLen / 4u; k &gt; 4u; k &gt;&gt;= 2u)
    1264. 

  1264. <a name="l01261"></a>01261   {
    1265. 

  1265. <a name="l01262"></a>01262     <span class="comment">/*  Initializations for the middle stage */</span>
    1266. 

  1266. <a name="l01263"></a>01263     n1 = n2;
    1267. 

  1267. <a name="l01264"></a>01264     n2 &gt;&gt;= 2u;
    1268. 

  1268. <a name="l01265"></a>01265     ic = 0u;
    1269. 

  1269. <a name="l01266"></a>01266 
    1270. 

  1270. <a name="l01267"></a>01267     <span class="keywordflow">for</span> (j = 0u; j &lt;= (n2 - 1u); j++)
    1271. 

  1271. <a name="l01268"></a>01268     {
    1272. 

  1272. <a name="l01269"></a>01269       <span class="comment">/*  index calculation for the coefficients */</span>
    1273. 

  1273. <a name="l01270"></a>01270       C1 = pCoeff[ic];
    1274. 

  1274. <a name="l01271"></a>01271       C2 = pCoeff[2u * ic];
    1275. 

  1275. <a name="l01272"></a>01272       C3 = pCoeff[3u * ic];
    1276. 

  1276. <a name="l01273"></a>01273 
    1277. 

  1277. <a name="l01274"></a>01274       <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1278. 

  1278. <a name="l01275"></a>01275       ic = ic + twidCoefModifier;
    1279. 

  1279. <a name="l01276"></a>01276 
    1280. 

  1280. <a name="l01277"></a>01277       <span class="comment">/*  Butterfly implementation */</span>
    1281. 

  1281. <a name="l01278"></a>01278       <span class="keywordflow">for</span> (i0 = j; i0 &lt; fftLen; i0 += n1)
    1282. 

  1282. <a name="l01279"></a>01279       {
    1283. 

  1283. <a name="l01280"></a>01280         <span class="comment">/*  index calculation for the input as, */</span>
    1284. 

  1284. <a name="l01281"></a>01281         <span class="comment">/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */</span>
    1285. 

  1285. <a name="l01282"></a>01282         i1 = i0 + n2;
    1286. 

  1286. <a name="l01283"></a>01283         i2 = i1 + n2;
    1287. 

  1287. <a name="l01284"></a>01284         i3 = i2 + n2;
    1288. 

  1288. <a name="l01285"></a>01285 
    1289. 

  1289. <a name="l01286"></a>01286         <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    1290. 

  1290. <a name="l01287"></a>01287         <span class="comment">/* Read ya (real), xa(imag) input */</span>
    1291. 

  1291. <a name="l01288"></a>01288         T = pSrc[i0];
    1292. 

  1292. <a name="l01289"></a>01289 
    1293. 

  1293. <a name="l01290"></a>01290         <span class="comment">/* Read yc (real), xc(imag) input */</span>
    1294. 

  1294. <a name="l01291"></a>01291         S = pSrc[i2];
    1295. 

  1295. <a name="l01292"></a>01292 
    1296. 

  1296. <a name="l01293"></a>01293 
    1297. 

  1297. <a name="l01294"></a>01294         <span class="comment">/* R = packed( (ya + yc), (xa + xc)) */</span>
    1298. 

  1298. <a name="l01295"></a>01295         R = __QADD16(T, S);
    1299. 

  1299. <a name="l01296"></a>01296         <span class="comment">/* S = packed((ya - yc), (xa - xc)) */</span>
    1300. 

  1300. <a name="l01297"></a>01297         S = __QSUB16(T, S);
    1301. 

  1301. <a name="l01298"></a>01298 
    1302. 

  1302. <a name="l01299"></a>01299         <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    1303. 

  1303. <a name="l01300"></a>01300         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1304. 

  1304. <a name="l01301"></a>01301         T = pSrc[i1];
    1305. 

  1305. <a name="l01302"></a>01302 
    1306. 

  1306. <a name="l01303"></a>01303         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1307. 

  1307. <a name="l01304"></a>01304         U = pSrc[i3];
    1308. 

  1308. <a name="l01305"></a>01305 
    1309. 

  1309. <a name="l01306"></a>01306 
    1310. 

  1310. <a name="l01307"></a>01307         <span class="comment">/* T = packed( (yb + yd), (xb + xd)) */</span>
    1311. 

  1311. <a name="l01308"></a>01308         T = __QADD16(T, U);
    1312. 

  1312. <a name="l01309"></a>01309 
    1313. 

  1313. <a name="l01310"></a>01310         <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    1314. 

  1314. <a name="l01311"></a>01311         <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    1315. 

  1315. <a name="l01312"></a>01312         <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    1316. 

  1316. <a name="l01313"></a>01313         out1 = __SHADD16(R, T);
    1317. 

  1317. <a name="l01314"></a>01314         in = ((int16_t) (out1 &amp; 0xFFFF)) &gt;&gt; 1;
    1318. 

  1318. <a name="l01315"></a>01315         out1 = ((out1 &gt;&gt; 1) &amp; 0xFFFF0000) | (in &amp; 0xFFFF);
    1319. 

  1319. <a name="l01316"></a>01316         pSrc[i0] = out1;
    1320. 

  1320. <a name="l01317"></a>01317 
    1321. 

  1321. <a name="l01318"></a>01318 
    1322. 

  1322. <a name="l01319"></a>01319 
    1323. 

  1323. <a name="l01320"></a>01320         <span class="comment">/* R = packed( (ya + yc) - (yb + yd), (xa + xc) - (xb + xd)) */</span>
    1324. 

  1324. <a name="l01321"></a>01321         R = __SHSUB16(R, T);
    1325. 

  1325. <a name="l01322"></a>01322 
    1326. 

  1326. <a name="l01323"></a>01323 
    1327. 

  1327. <a name="l01324"></a>01324 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1328. 

  1328. <a name="l01325"></a>01325 <span class="preprocessor"></span>
    1329. 

  1329. <a name="l01326"></a>01326         <span class="comment">/* (ya-yb+yc-yd)* (si2) - (xa-xb+xc-xd)* co2 */</span>
    1330. 

  1330. <a name="l01327"></a>01327         out1 = __SMUSD(C2, R) &gt;&gt; 16u;
    1331. 

  1331. <a name="l01328"></a>01328         <span class="comment">/* (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1332. 

  1332. <a name="l01329"></a>01329         out2 = __SMUADX(C2, R);
    1333. 

  1333. <a name="l01330"></a>01330 
    1334. 

  1334. <a name="l01331"></a>01331 <span class="preprocessor">#else</span>
    1335. 

  1335. <a name="l01332"></a>01332 <span class="preprocessor"></span>
    1336. 

  1336. <a name="l01333"></a>01333         <span class="comment">/* (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1337. 

  1337. <a name="l01334"></a>01334         out1 = __SMUADX(R, C2) &gt;&gt; 16u;
    1338. 

  1338. <a name="l01335"></a>01335         <span class="comment">/* (ya-yb+yc-yd)* (si2) - (xa-xb+xc-xd)* co2 */</span>
    1339. 

  1339. <a name="l01336"></a>01336         out2 = __SMUSD(-C2, R);
    1340. 

  1340. <a name="l01337"></a>01337 
    1341. 

  1341. <a name="l01338"></a>01338 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1342. 

  1342. <a name="l01339"></a>01339 
    1343. 

  1343. <a name="l01340"></a>01340         <span class="comment">/*  Reading i0+3fftLen/4 */</span>
    1344. 

  1344. <a name="l01341"></a>01341         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1345. 

  1345. <a name="l01342"></a>01342         T = pSrc[i1];
    1346. 

  1346. <a name="l01343"></a>01343 
    1347. 

  1347. <a name="l01344"></a>01344         <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    1348. 

  1348. <a name="l01345"></a>01345         <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) */</span>
    1349. 

  1349. <a name="l01346"></a>01346         <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1350. 

  1350. <a name="l01347"></a>01347         pSrc[i1] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    1351. 

  1351. <a name="l01348"></a>01348 
    1352. 

  1352. <a name="l01349"></a>01349         <span class="comment">/*  Butterfly calculations */</span>
    1353. 

  1353. <a name="l01350"></a>01350         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1354. 

  1354. <a name="l01351"></a>01351         U = pSrc[i3];
    1355. 

  1355. <a name="l01352"></a>01352 
    1356. 

  1356. <a name="l01353"></a>01353         <span class="comment">/* T = packed(yb-yd, xb-xd) */</span>
    1357. 

  1357. <a name="l01354"></a>01354         T = __QSUB16(T, U);
    1358. 

  1358. <a name="l01355"></a>01355 
    1359. 

  1359. <a name="l01356"></a>01356 
    1360. 

  1360. <a name="l01357"></a>01357 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1361. 

  1361. <a name="l01358"></a>01358 <span class="preprocessor"></span>
    1362. 

  1362. <a name="l01359"></a>01359         <span class="comment">/* R = packed((ya-yc) - (xb- xd) , (xa-xc) + (yb-yd)) */</span>
    1363. 

  1363. <a name="l01360"></a>01360         R = __SHSAX(S, T);
    1364. 

  1364. <a name="l01361"></a>01361 
    1365. 

  1365. <a name="l01362"></a>01362         <span class="comment">/* S = packed((ya-yc) + (xb- xd),  (xa-xc) - (yb-yd)) */</span>
    1366. 

  1366. <a name="l01363"></a>01363         S = __SHASX(S, T);
    1367. 

  1367. <a name="l01364"></a>01364         <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    1368. 

  1368. <a name="l01365"></a>01365         out1 = __SMUSD(C1, S) &gt;&gt; 16u;
    1369. 

  1369. <a name="l01366"></a>01366         out2 = __SMUADX(C1, S);
    1370. 

  1370. <a name="l01367"></a>01367 
    1371. 

  1371. <a name="l01368"></a>01368 <span class="preprocessor">#else</span>
    1372. 

  1372. <a name="l01369"></a>01369 <span class="preprocessor"></span>
    1373. 

  1373. <a name="l01370"></a>01370         <span class="comment">/* R = packed((ya-yc) - (xb- xd) , (xa-xc) + (yb-yd)) */</span>
    1374. 

  1374. <a name="l01371"></a>01371         R = __SHASX(S, T);
    1375. 

  1375. <a name="l01372"></a>01372 
    1376. 

  1376. <a name="l01373"></a>01373         <span class="comment">/* S = packed((ya-yc) + (xb- xd),  (xa-xc) - (yb-yd)) */</span>
    1377. 

  1377. <a name="l01374"></a>01374         S = __SHSAX(S, T);
    1378. 

  1378. <a name="l01375"></a>01375         <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    1379. 

  1379. <a name="l01376"></a>01376         out1 = __SMUADX(S, C1) &gt;&gt; 16u;
    1380. 

  1380. <a name="l01377"></a>01377         out2 = __SMUSD(-C1, S);
    1381. 

  1381. <a name="l01378"></a>01378 
    1382. 

  1382. <a name="l01379"></a>01379 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1383. 

  1383. <a name="l01380"></a>01380 
    1384. 

  1384. <a name="l01381"></a>01381         <span class="comment">/* xb&#39; = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) */</span>
    1385. 

  1385. <a name="l01382"></a>01382         <span class="comment">/* yb&#39; = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */</span>
    1386. 

  1386. <a name="l01383"></a>01383         pSrc[i2] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    1387. 

  1387. <a name="l01384"></a>01384 
    1388. 

  1388. <a name="l01385"></a>01385         <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    1389. 

  1389. <a name="l01386"></a>01386 
    1390. 

  1390. <a name="l01387"></a>01387 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1391. 

  1391. <a name="l01388"></a>01388 <span class="preprocessor"></span>
    1392. 

  1392. <a name="l01389"></a>01389         out1 = __SMUSD(C3, R) &gt;&gt; 16u;
    1393. 

  1393. <a name="l01390"></a>01390         out2 = __SMUADX(C3, R);
    1394. 

  1394. <a name="l01391"></a>01391 
    1395. 

  1395. <a name="l01392"></a>01392 <span class="preprocessor">#else</span>
    1396. 

  1396. <a name="l01393"></a>01393 <span class="preprocessor"></span>
    1397. 

  1397. <a name="l01394"></a>01394         out1 = __SMUADX(C3, R) &gt;&gt; 16u;
    1398. 

  1398. <a name="l01395"></a>01395         out2 = __SMUSD(-C3, R);
    1399. 

  1399. <a name="l01396"></a>01396 
    1400. 

  1400. <a name="l01397"></a>01397 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1401. 

  1401. <a name="l01398"></a>01398 
    1402. 

  1402. <a name="l01399"></a>01399         <span class="comment">/* xd&#39; = (xa+yb-xc-yd)* co3 - (ya-xb-yc+xd)* (si3) */</span>
    1403. 

  1403. <a name="l01400"></a>01400         <span class="comment">/* yd&#39; = (ya-xb-yc+xd)* co3 + (xa+yb-xc-yd)* (si3) */</span>
    1404. 

  1404. <a name="l01401"></a>01401         pSrc[i3] = ((out2) &amp; 0xFFFF0000) | (out1 &amp; 0x0000FFFF);
    1405. 

  1405. <a name="l01402"></a>01402 
    1406. 

  1406. <a name="l01403"></a>01403 
    1407. 

  1407. <a name="l01404"></a>01404       }
    1408. 

  1408. <a name="l01405"></a>01405     }
    1409. 

  1409. <a name="l01406"></a>01406     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1410. 

  1410. <a name="l01407"></a>01407     twidCoefModifier &lt;&lt;= 2u;
    1411. 

  1411. <a name="l01408"></a>01408   }
    1412. 

  1412. <a name="l01409"></a>01409   <span class="comment">/*  End of Middle stages process */</span>
    1413. 

  1413. <a name="l01410"></a>01410 
    1414. 

  1414. <a name="l01411"></a>01411 
    1415. 

  1415. <a name="l01412"></a>01412   <span class="comment">/* data is in 10.6(q6) format for the 1024 point */</span>
    1416. 

  1416. <a name="l01413"></a>01413   <span class="comment">/* data is in 8.8(q8) format for the 256 point   */</span>
    1417. 

  1417. <a name="l01414"></a>01414   <span class="comment">/* data is in 6.10(q10) format for the 64 point  */</span>
    1418. 

  1418. <a name="l01415"></a>01415   <span class="comment">/* data is in 4.12(q12) format for the 16 point  */</span>
    1419. 

  1419. <a name="l01416"></a>01416 
    1420. 

  1420. <a name="l01417"></a>01417   <span class="comment">/* start of last stage process */</span>
    1421. 

  1421. <a name="l01418"></a>01418 
    1422. 

  1422. <a name="l01419"></a>01419 
    1423. 

  1423. <a name="l01420"></a>01420   <span class="comment">/*  Initializations for the last stage */</span>
    1424. 

  1424. <a name="l01421"></a>01421   n1 = n2;
    1425. 

  1425. <a name="l01422"></a>01422   n2 &gt;&gt;= 2u;
    1426. 

  1426. <a name="l01423"></a>01423 
    1427. 

  1427. <a name="l01424"></a>01424   <span class="comment">/*  Butterfly implementation */</span>
    1428. 

  1428. <a name="l01425"></a>01425   <span class="keywordflow">for</span> (i0 = 0u; i0 &lt;= (fftLen - n1); i0 += n1)
    1429. 

  1429. <a name="l01426"></a>01426   {
    1430. 

  1430. <a name="l01427"></a>01427     <span class="comment">/*  index calculation for the input as, */</span>
    1431. 

  1431. <a name="l01428"></a>01428     <span class="comment">/*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */</span>
    1432. 

  1432. <a name="l01429"></a>01429     i1 = i0 + n2;
    1433. 

  1433. <a name="l01430"></a>01430     i2 = i1 + n2;
    1434. 

  1434. <a name="l01431"></a>01431     i3 = i2 + n2;
    1435. 

  1435. <a name="l01432"></a>01432 
    1436. 

  1436. <a name="l01433"></a>01433     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    1437. 

  1437. <a name="l01434"></a>01434     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    1438. 

  1438. <a name="l01435"></a>01435     T = pSrc[i0];
    1439. 

  1439. <a name="l01436"></a>01436     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    1440. 

  1440. <a name="l01437"></a>01437     S = pSrc[i2];
    1441. 

  1441. <a name="l01438"></a>01438 
    1442. 

  1442. <a name="l01439"></a>01439     <span class="comment">/* R = packed((ya + yc), (xa + xc)) */</span>
    1443. 

  1443. <a name="l01440"></a>01440     R = __QADD16(T, S);
    1444. 

  1444. <a name="l01441"></a>01441     <span class="comment">/* S = packed((ya - yc), (xa - xc)) */</span>
    1445. 

  1445. <a name="l01442"></a>01442     S = __QSUB16(T, S);
    1446. 

  1446. <a name="l01443"></a>01443 
    1447. 

  1447. <a name="l01444"></a>01444     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    1448. 

  1448. <a name="l01445"></a>01445     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1449. 

  1449. <a name="l01446"></a>01446     T = pSrc[i1];
    1450. 

  1450. <a name="l01447"></a>01447     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1451. 

  1451. <a name="l01448"></a>01448     U = pSrc[i3];
    1452. 

  1452. <a name="l01449"></a>01449 
    1453. 

  1453. <a name="l01450"></a>01450     <span class="comment">/* T = packed((yb + yd), (xb + xd)) */</span>
    1454. 

  1454. <a name="l01451"></a>01451     T = __QADD16(T, U);
    1455. 

  1455. <a name="l01452"></a>01452 
    1456. 

  1456. <a name="l01453"></a>01453     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    1457. 

  1457. <a name="l01454"></a>01454     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    1458. 

  1458. <a name="l01455"></a>01455     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    1459. 

  1459. <a name="l01456"></a>01456     pSrc[i0] = __SHADD16(R, T);
    1460. 

  1460. <a name="l01457"></a>01457 
    1461. 

  1461. <a name="l01458"></a>01458     <span class="comment">/* R = packed((ya + yc) - (yb + yd), (xa + xc) - (xb + xd)) */</span>
    1462. 

  1462. <a name="l01459"></a>01459     R = __SHSUB16(R, T);
    1463. 

  1463. <a name="l01460"></a>01460 
    1464. 

  1464. <a name="l01461"></a>01461     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1465. 

  1465. <a name="l01462"></a>01462     T = pSrc[i1];
    1466. 

  1466. <a name="l01463"></a>01463 
    1467. 

  1467. <a name="l01464"></a>01464     <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    1468. 

  1468. <a name="l01465"></a>01465     <span class="comment">/* xc&#39; = (xa-xb+xc-xd) */</span>
    1469. 

  1469. <a name="l01466"></a>01466     <span class="comment">/* yc&#39; = (ya-yb+yc-yd) */</span>
    1470. 

  1470. <a name="l01467"></a>01467     pSrc[i1] = R;
    1471. 

  1471. <a name="l01468"></a>01468 
    1472. 

  1472. <a name="l01469"></a>01469     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1473. 

  1473. <a name="l01470"></a>01470     U = pSrc[i3];
    1474. 

  1474. <a name="l01471"></a>01471     <span class="comment">/* T = packed( (yb - yd), (xb - xd))  */</span>
    1475. 

  1475. <a name="l01472"></a>01472     T = __QSUB16(T, U);
    1476. 

  1476. <a name="l01473"></a>01473 
    1477. 

  1477. <a name="l01474"></a>01474 
    1478. 

  1478. <a name="l01475"></a>01475 <span class="preprocessor">#ifndef ARM_MATH_BIG_ENDIAN</span>
    1479. 

  1479. <a name="l01476"></a>01476 <span class="preprocessor"></span>
    1480. 

  1480. <a name="l01477"></a>01477     <span class="comment">/*  writing the butterfly processed i0 + fftLen/2 sample */</span>
    1481. 

  1481. <a name="l01478"></a>01478     <span class="comment">/* xb&#39; = (xa-yb-xc+yd) */</span>
    1482. 

  1482. <a name="l01479"></a>01479     <span class="comment">/* yb&#39; = (ya+xb-yc-xd) */</span>
    1483. 

  1483. <a name="l01480"></a>01480     pSrc[i2] = __SHASX(S, T);
    1484. 

  1484. <a name="l01481"></a>01481 
    1485. 

  1485. <a name="l01482"></a>01482     <span class="comment">/*  writing the butterfly processed i0 + 3fftLen/4 sample */</span>
    1486. 

  1486. <a name="l01483"></a>01483     <span class="comment">/* xd&#39; = (xa+yb-xc-yd) */</span>
    1487. 

  1487. <a name="l01484"></a>01484     <span class="comment">/* yd&#39; = (ya-xb-yc+xd) */</span>
    1488. 

  1488. <a name="l01485"></a>01485     pSrc[i3] = __SHSAX(S, T);
    1489. 

  1489. <a name="l01486"></a>01486 
    1490. 

  1490. <a name="l01487"></a>01487 
    1491. 

  1491. <a name="l01488"></a>01488 <span class="preprocessor">#else</span>
    1492. 

  1492. <a name="l01489"></a>01489 <span class="preprocessor"></span>
    1493. 

  1493. <a name="l01490"></a>01490     <span class="comment">/*  writing the butterfly processed i0 + fftLen/2 sample */</span>
    1494. 

  1494. <a name="l01491"></a>01491     <span class="comment">/* xb&#39; = (xa-yb-xc+yd) */</span>
    1495. 

  1495. <a name="l01492"></a>01492     <span class="comment">/* yb&#39; = (ya+xb-yc-xd) */</span>
    1496. 

  1496. <a name="l01493"></a>01493     pSrc[i2] = __SHSAX(S, T);
    1497. 

  1497. <a name="l01494"></a>01494 
    1498. 

  1498. <a name="l01495"></a>01495     <span class="comment">/*  writing the butterfly processed i0 + 3fftLen/4 sample */</span>
    1499. 

  1499. <a name="l01496"></a>01496     <span class="comment">/* xd&#39; = (xa+yb-xc-yd) */</span>
    1500. 

  1500. <a name="l01497"></a>01497     <span class="comment">/* yd&#39; = (ya-xb-yc+xd) */</span>
    1501. 

  1501. <a name="l01498"></a>01498     pSrc[i3] = __SHASX(S, T);
    1502. 

  1502. <a name="l01499"></a>01499 
    1503. 

  1503. <a name="l01500"></a>01500 <span class="preprocessor">#endif </span><span class="comment">/*      #ifndef ARM_MATH_BIG_ENDIAN     */</span>
    1504. 

  1504. <a name="l01501"></a>01501 
    1505. 

  1505. <a name="l01502"></a>01502   }
    1506. 

  1506. <a name="l01503"></a>01503   <span class="comment">/* end of last stage  process */</span>
    1507. 

  1507. <a name="l01504"></a>01504 
    1508. 

  1508. <a name="l01505"></a>01505   <span class="comment">/* output is in 11.5(q5) format for the 1024 point */</span>
    1509. 

  1509. <a name="l01506"></a>01506   <span class="comment">/* output is in 9.7(q7) format for the 256 point   */</span>
    1510. 

  1510. <a name="l01507"></a>01507   <span class="comment">/* output is in 7.9(q9) format for the 64 point  */</span>
    1511. 

  1511. <a name="l01508"></a>01508   <span class="comment">/* output is in 5.11(q11) format for the 16 point  */</span>
    1512. 

  1512. <a name="l01509"></a>01509 
    1513. 

  1513. <a name="l01510"></a>01510 
    1514. 

  1514. <a name="l01511"></a>01511 <span class="preprocessor">#else</span>
    1515. 

  1515. <a name="l01512"></a>01512 <span class="preprocessor"></span>
    1516. 

  1516. <a name="l01513"></a>01513   <span class="comment">/* Run the below code for Cortex-M0 */</span>
    1517. 

  1517. <a name="l01514"></a>01514 
    1518. 

  1518. <a name="l01515"></a>01515   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> R0, R1, S0, S1, T0, T1, U0, U1;
    1519. 

  1519. <a name="l01516"></a>01516   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> Co1, Si1, Co2, Si2, Co3, Si3, out1, out2;
    1520. 

  1520. <a name="l01517"></a>01517   uint32_t n1, n2, ic, i0, i1, i2, i3, j, k;
    1521. 

  1521. <a name="l01518"></a>01518 
    1522. 

  1522. <a name="l01519"></a>01519   <span class="comment">/* Total process is divided into three stages */</span>
    1523. 

  1523. <a name="l01520"></a>01520 
    1524. 

  1524. <a name="l01521"></a>01521   <span class="comment">/* process first stage, middle stages, &amp; last stage */</span>
    1525. 

  1525. <a name="l01522"></a>01522 
    1526. 

  1526. <a name="l01523"></a>01523   <span class="comment">/*  Initializations for the first stage */</span>
    1527. 

  1527. <a name="l01524"></a>01524   n2 = fftLen;
    1528. 

  1528. <a name="l01525"></a>01525   n1 = n2;
    1529. 

  1529. <a name="l01526"></a>01526 
    1530. 

  1530. <a name="l01527"></a>01527   <span class="comment">/* n2 = fftLen/4 */</span>
    1531. 

  1531. <a name="l01528"></a>01528   n2 &gt;&gt;= 2u;
    1532. 

  1532. <a name="l01529"></a>01529 
    1533. 

  1533. <a name="l01530"></a>01530   <span class="comment">/* Index for twiddle coefficient */</span>
    1534. 

  1534. <a name="l01531"></a>01531   ic = 0u;
    1535. 

  1535. <a name="l01532"></a>01532 
    1536. 

  1536. <a name="l01533"></a>01533   <span class="comment">/* Index for input read and output write */</span>
    1537. 

  1537. <a name="l01534"></a>01534   i0 = 0u;
    1538. 

  1538. <a name="l01535"></a>01535 
    1539. 

  1539. <a name="l01536"></a>01536   j = n2;
    1540. 

  1540. <a name="l01537"></a>01537 
    1541. 

  1541. <a name="l01538"></a>01538   <span class="comment">/* Input is in 1.15(q15) format */</span>
    1542. 

  1542. <a name="l01539"></a>01539 
    1543. 

  1543. <a name="l01540"></a>01540   <span class="comment">/*  Start of first stage process */</span>
    1544. 

  1544. <a name="l01541"></a>01541   <span class="keywordflow">do</span>
    1545. 

  1545. <a name="l01542"></a>01542   {
    1546. 

  1546. <a name="l01543"></a>01543     <span class="comment">/*  Butterfly implementation */</span>
    1547. 

  1547. <a name="l01544"></a>01544 
    1548. 

  1548. <a name="l01545"></a>01545     <span class="comment">/*  index calculation for the input as, */</span>
    1549. 

  1549. <a name="l01546"></a>01546     <span class="comment">/*  pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */</span>
    1550. 

  1550. <a name="l01547"></a>01547     i1 = i0 + n2;
    1551. 

  1551. <a name="l01548"></a>01548     i2 = i1 + n2;
    1552. 

  1552. <a name="l01549"></a>01549     i3 = i2 + n2;
    1553. 

  1553. <a name="l01550"></a>01550 
    1554. 

  1554. <a name="l01551"></a>01551     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    1555. 

  1555. <a name="l01552"></a>01552     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    1556. 

  1556. <a name="l01553"></a>01553     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    1557. 

  1557. <a name="l01554"></a>01554     T0 = pSrc16[i0 * 2u] &gt;&gt; 2u;
    1558. 

  1558. <a name="l01555"></a>01555     T1 = pSrc16[(i0 * 2u) + 1u] &gt;&gt; 2u;
    1559. 

  1559. <a name="l01556"></a>01556     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    1560. 

  1560. <a name="l01557"></a>01557     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    1561. 

  1561. <a name="l01558"></a>01558     S0 = pSrc16[i2 * 2u] &gt;&gt; 2u;
    1562. 

  1562. <a name="l01559"></a>01559     S1 = pSrc16[(i2 * 2u) + 1u] &gt;&gt; 2u;
    1563. 

  1563. <a name="l01560"></a>01560 
    1564. 

  1564. <a name="l01561"></a>01561     <span class="comment">/* R0 = (ya + yc), R1 = (xa + xc) */</span>
    1565. 

  1565. <a name="l01562"></a>01562     R0 = __SSAT(T0 + S0, 16u);
    1566. 

  1566. <a name="l01563"></a>01563     R1 = __SSAT(T1 + S1, 16u);
    1567. 

  1567. <a name="l01564"></a>01564     <span class="comment">/* S0 = (ya - yc), S1 = (xa - xc) */</span>
    1568. 

  1568. <a name="l01565"></a>01565     S0 = __SSAT(T0 - S0, 16u);
    1569. 

  1569. <a name="l01566"></a>01566     S1 = __SSAT(T1 - S1, 16u);
    1570. 

  1570. <a name="l01567"></a>01567 
    1571. 

  1571. <a name="l01568"></a>01568     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    1572. 

  1572. <a name="l01569"></a>01569     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    1573. 

  1573. <a name="l01570"></a>01570     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1574. 

  1574. <a name="l01571"></a>01571     T0 = pSrc16[i1 * 2u] &gt;&gt; 2u;
    1575. 

  1575. <a name="l01572"></a>01572     T1 = pSrc16[(i1 * 2u) + 1u] &gt;&gt; 2u;
    1576. 

  1576. <a name="l01573"></a>01573     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1577. 

  1577. <a name="l01574"></a>01574     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    1578. 

  1578. <a name="l01575"></a>01575     U0 = pSrc16[i3 * 2u] &gt;&gt; 2u;
    1579. 

  1579. <a name="l01576"></a>01576     U1 = pSrc16[(i3 * 2u) + 1u] &gt;&gt; 2u;
    1580. 

  1580. <a name="l01577"></a>01577 
    1581. 

  1581. <a name="l01578"></a>01578     <span class="comment">/* T0 = (yb + yd), T1 = (xb + xd) */</span>
    1582. 

  1582. <a name="l01579"></a>01579     T0 = __SSAT(T0 + U0, 16u);
    1583. 

  1583. <a name="l01580"></a>01580     T1 = __SSAT(T1 + U1, 16u);
    1584. 

  1584. <a name="l01581"></a>01581 
    1585. 

  1585. <a name="l01582"></a>01582     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    1586. 

  1586. <a name="l01583"></a>01583     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    1587. 

  1587. <a name="l01584"></a>01584     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    1588. 

  1588. <a name="l01585"></a>01585     pSrc16[i0 * 2u] = (R0 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    1589. 

  1589. <a name="l01586"></a>01586     pSrc16[(i0 * 2u) + 1u] = (R1 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    1590. 

  1590. <a name="l01587"></a>01587 
    1591. 

  1591. <a name="l01588"></a>01588     <span class="comment">/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc)- (xb + xd) */</span>
    1592. 

  1592. <a name="l01589"></a>01589     R0 = __SSAT(R0 - T0, 16u);
    1593. 

  1593. <a name="l01590"></a>01590     R1 = __SSAT(R1 - T1, 16u);
    1594. 

  1594. <a name="l01591"></a>01591     <span class="comment">/* co2 &amp; si2 are read from Coefficient pointer */</span>
    1595. 

  1595. <a name="l01592"></a>01592     Co2 = pCoef16[2u * ic * 2u];
    1596. 

  1596. <a name="l01593"></a>01593     Si2 = pCoef16[(2u * ic * 2u) + 1u];
    1597. 

  1597. <a name="l01594"></a>01594     <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) */</span>
    1598. 

  1598. <a name="l01595"></a>01595     out1 = (short) ((Co2 * R0 - Si2 * R1) &gt;&gt; 16u);
    1599. 

  1599. <a name="l01596"></a>01596     <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1600. 

  1600. <a name="l01597"></a>01597     out2 = (short) ((Si2 * R0 + Co2 * R1) &gt;&gt; 16u);
    1601. 

  1601. <a name="l01598"></a>01598 
    1602. 

  1602. <a name="l01599"></a>01599     <span class="comment">/*  Reading i0+fftLen/4 */</span>
    1603. 

  1603. <a name="l01600"></a>01600     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    1604. 

  1604. <a name="l01601"></a>01601     <span class="comment">/* T0 = yb, T1 = xb */</span>
    1605. 

  1605. <a name="l01602"></a>01602     T0 = pSrc16[i1 * 2u] &gt;&gt; 2u;
    1606. 

  1606. <a name="l01603"></a>01603     T1 = pSrc16[(i1 * 2u) + 1u] &gt;&gt; 2u;
    1607. 

  1607. <a name="l01604"></a>01604 
    1608. 

  1608. <a name="l01605"></a>01605     <span class="comment">/* writing the butterfly processed i0 + fftLen/4 sample */</span>
    1609. 

  1609. <a name="l01606"></a>01606     <span class="comment">/* writing output(xc&#39;, yc&#39;) in little endian format */</span>
    1610. 

  1610. <a name="l01607"></a>01607     pSrc16[i1 * 2u] = out1;
    1611. 

  1611. <a name="l01608"></a>01608     pSrc16[(i1 * 2u) + 1u] = out2;
    1612. 

  1612. <a name="l01609"></a>01609 
    1613. 

  1613. <a name="l01610"></a>01610     <span class="comment">/*  Butterfly calculations */</span>
    1614. 

  1614. <a name="l01611"></a>01611     <span class="comment">/* input is down scale by 4 to avoid overflow */</span>
    1615. 

  1615. <a name="l01612"></a>01612     <span class="comment">/* U0 = yd, U1 = xd) */</span>
    1616. 

  1616. <a name="l01613"></a>01613     U0 = pSrc16[i3 * 2u] &gt;&gt; 2u;
    1617. 

  1617. <a name="l01614"></a>01614     U1 = pSrc16[(i3 * 2u) + 1u] &gt;&gt; 2u;
    1618. 

  1618. <a name="l01615"></a>01615 
    1619. 

  1619. <a name="l01616"></a>01616     <span class="comment">/* T0 = yb-yd, T1 = xb-xd) */</span>
    1620. 

  1620. <a name="l01617"></a>01617     T0 = __SSAT(T0 - U0, 16u);
    1621. 

  1621. <a name="l01618"></a>01618     T1 = __SSAT(T1 - U1, 16u);
    1622. 

  1622. <a name="l01619"></a>01619     <span class="comment">/* R0 = (ya-yc) - (xb- xd) , R1 = (xa-xc) + (yb-yd) */</span>
    1623. 

  1623. <a name="l01620"></a>01620     R0 = (short) __SSAT((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) (S0 + T1), 16);
    1624. 

  1624. <a name="l01621"></a>01621     R1 = (short) __SSAT((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) (S1 - T0), 16);
    1625. 

  1625. <a name="l01622"></a>01622     <span class="comment">/* S = (ya-yc) + (xb- xd), S1 = (xa-xc) - (yb-yd) */</span>
    1626. 

  1626. <a name="l01623"></a>01623     S0 = (short) __SSAT((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) (S0 - T1), 16);
    1627. 

  1627. <a name="l01624"></a>01624     S1 = (short) __SSAT((<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) (S1 + T0), 16);
    1628. 

  1628. <a name="l01625"></a>01625 
    1629. 

  1629. <a name="l01626"></a>01626     <span class="comment">/* co1 &amp; si1 are read from Coefficient pointer */</span>
    1630. 

  1630. <a name="l01627"></a>01627     Co1 = pCoef16[ic * 2u];
    1631. 

  1631. <a name="l01628"></a>01628     Si1 = pCoef16[(ic * 2u) + 1u];
    1632. 

  1632. <a name="l01629"></a>01629     <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    1633. 

  1633. <a name="l01630"></a>01630     <span class="comment">/* xb&#39; = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) */</span>
    1634. 

  1634. <a name="l01631"></a>01631     out1 = (short) ((Co1 * S0 - Si1 * S1) &gt;&gt; 16u);
    1635. 

  1635. <a name="l01632"></a>01632     <span class="comment">/* yb&#39; = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */</span>
    1636. 

  1636. <a name="l01633"></a>01633     out2 = (short) ((Si1 * S0 + Co1 * S1) &gt;&gt; 16u);
    1637. 

  1637. <a name="l01634"></a>01634     <span class="comment">/* writing output(xb&#39;, yb&#39;) in little endian format */</span>
    1638. 

  1638. <a name="l01635"></a>01635     pSrc16[i2 * 2u] = out1;
    1639. 

  1639. <a name="l01636"></a>01636     pSrc16[(i2 * 2u) + 1u] = out2;
    1640. 

  1640. <a name="l01637"></a>01637 
    1641. 

  1641. <a name="l01638"></a>01638     <span class="comment">/* Co3 &amp; si3 are read from Coefficient pointer */</span>
    1642. 

  1642. <a name="l01639"></a>01639     Co3 = pCoef16[3u * ic * 2u];
    1643. 

  1643. <a name="l01640"></a>01640     Si3 = pCoef16[(3u * ic * 2u) + 1u];
    1644. 

  1644. <a name="l01641"></a>01641     <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    1645. 

  1645. <a name="l01642"></a>01642     <span class="comment">/* xd&#39; = (xa+yb-xc-yd)* Co3 - (ya-xb-yc+xd)* (si3) */</span>
    1646. 

  1646. <a name="l01643"></a>01643     out1 = (short) ((Co3 * R0 - Si3 * R1) &gt;&gt; 16u);
    1647. 

  1647. <a name="l01644"></a>01644     <span class="comment">/* yd&#39; = (ya-xb-yc+xd)* Co3 + (xa+yb-xc-yd)* (si3) */</span>
    1648. 

  1648. <a name="l01645"></a>01645     out2 = (short) ((Si3 * R0 + Co3 * R1) &gt;&gt; 16u);
    1649. 

  1649. <a name="l01646"></a>01646     <span class="comment">/* writing output(xd&#39;, yd&#39;) in little endian format */</span>
    1650. 

  1650. <a name="l01647"></a>01647     pSrc16[i3 * 2u] = out1;
    1651. 

  1651. <a name="l01648"></a>01648     pSrc16[(i3 * 2u) + 1u] = out2;
    1652. 

  1652. <a name="l01649"></a>01649 
    1653. 

  1653. <a name="l01650"></a>01650     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1654. 

  1654. <a name="l01651"></a>01651     ic = ic + twidCoefModifier;
    1655. 

  1655. <a name="l01652"></a>01652 
    1656. 

  1656. <a name="l01653"></a>01653     <span class="comment">/*  Updating input index */</span>
    1657. 

  1657. <a name="l01654"></a>01654     i0 = i0 + 1u;
    1658. 

  1658. <a name="l01655"></a>01655 
    1659. 

  1659. <a name="l01656"></a>01656   } <span class="keywordflow">while</span>(--j);
    1660. 

  1660. <a name="l01657"></a>01657 
    1661. 

  1661. <a name="l01658"></a>01658   <span class="comment">/*  End of first stage process */</span>
    1662. 

  1662. <a name="l01659"></a>01659 
    1663. 

  1663. <a name="l01660"></a>01660   <span class="comment">/* data is in 4.11(q11) format */</span>
    1664. 

  1664. <a name="l01661"></a>01661 
    1665. 

  1665. <a name="l01662"></a>01662 
    1666. 

  1666. <a name="l01663"></a>01663   <span class="comment">/*  Start of Middle stage process */</span>
    1667. 

  1667. <a name="l01664"></a>01664 
    1668. 

  1668. <a name="l01665"></a>01665   <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1669. 

  1669. <a name="l01666"></a>01666   twidCoefModifier &lt;&lt;= 2u;
    1670. 

  1670. <a name="l01667"></a>01667 
    1671. 

  1671. <a name="l01668"></a>01668   <span class="comment">/*  Calculation of Middle stage */</span>
    1672. 

  1672. <a name="l01669"></a>01669   <span class="keywordflow">for</span> (k = fftLen / 4u; k &gt; 4u; k &gt;&gt;= 2u)
    1673. 

  1673. <a name="l01670"></a>01670   {
    1674. 

  1674. <a name="l01671"></a>01671     <span class="comment">/*  Initializations for the middle stage */</span>
    1675. 

  1675. <a name="l01672"></a>01672     n1 = n2;
    1676. 

  1676. <a name="l01673"></a>01673     n2 &gt;&gt;= 2u;
    1677. 

  1677. <a name="l01674"></a>01674     ic = 0u;
    1678. 

  1678. <a name="l01675"></a>01675 
    1679. 

  1679. <a name="l01676"></a>01676     <span class="keywordflow">for</span> (j = 0u; j &lt;= (n2 - 1u); j++)
    1680. 

  1680. <a name="l01677"></a>01677     {
    1681. 

  1681. <a name="l01678"></a>01678       <span class="comment">/*  index calculation for the coefficients */</span>
    1682. 

  1682. <a name="l01679"></a>01679       Co1 = pCoef16[ic * 2u];
    1683. 

  1683. <a name="l01680"></a>01680       Si1 = pCoef16[(ic * 2u) + 1u];
    1684. 

  1684. <a name="l01681"></a>01681       Co2 = pCoef16[2u * ic * 2u];
    1685. 

  1685. <a name="l01682"></a>01682       Si2 = pCoef16[2u * ic * 2u + 1u];
    1686. 

  1686. <a name="l01683"></a>01683       Co3 = pCoef16[3u * ic * 2u];
    1687. 

  1687. <a name="l01684"></a>01684       Si3 = pCoef16[(3u * ic * 2u) + 1u];
    1688. 

  1688. <a name="l01685"></a>01685 
    1689. 

  1689. <a name="l01686"></a>01686       <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1690. 

  1690. <a name="l01687"></a>01687       ic = ic + twidCoefModifier;
    1691. 

  1691. <a name="l01688"></a>01688 
    1692. 

  1692. <a name="l01689"></a>01689       <span class="comment">/*  Butterfly implementation */</span>
    1693. 

  1693. <a name="l01690"></a>01690       <span class="keywordflow">for</span> (i0 = j; i0 &lt; fftLen; i0 += n1)
    1694. 

  1694. <a name="l01691"></a>01691       {
    1695. 

  1695. <a name="l01692"></a>01692         <span class="comment">/*  index calculation for the input as, */</span>
    1696. 

  1696. <a name="l01693"></a>01693         <span class="comment">/*  pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */</span>
    1697. 

  1697. <a name="l01694"></a>01694         i1 = i0 + n2;
    1698. 

  1698. <a name="l01695"></a>01695         i2 = i1 + n2;
    1699. 

  1699. <a name="l01696"></a>01696         i3 = i2 + n2;
    1700. 

  1700. <a name="l01697"></a>01697 
    1701. 

  1701. <a name="l01698"></a>01698         <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    1702. 

  1702. <a name="l01699"></a>01699         <span class="comment">/* Read ya (real), xa(imag) input */</span>
    1703. 

  1703. <a name="l01700"></a>01700         T0 = pSrc16[i0 * 2u];
    1704. 

  1704. <a name="l01701"></a>01701         T1 = pSrc16[(i0 * 2u) + 1u];
    1705. 

  1705. <a name="l01702"></a>01702 
    1706. 

  1706. <a name="l01703"></a>01703         <span class="comment">/* Read yc (real), xc(imag) input */</span>
    1707. 

  1707. <a name="l01704"></a>01704         S0 = pSrc16[i2 * 2u];
    1708. 

  1708. <a name="l01705"></a>01705         S1 = pSrc16[(i2 * 2u) + 1u];
    1709. 

  1709. <a name="l01706"></a>01706 
    1710. 

  1710. <a name="l01707"></a>01707 
    1711. 

  1711. <a name="l01708"></a>01708         <span class="comment">/* R0 = (ya + yc), R1 = (xa + xc) */</span>
    1712. 

  1712. <a name="l01709"></a>01709         R0 = __SSAT(T0 + S0, 16u);
    1713. 

  1713. <a name="l01710"></a>01710         R1 = __SSAT(T1 + S1, 16u);
    1714. 

  1714. <a name="l01711"></a>01711         <span class="comment">/* S0 = (ya - yc), S1 = (xa - xc) */</span>
    1715. 

  1715. <a name="l01712"></a>01712         S0 = __SSAT(T0 - S0, 16u);
    1716. 

  1716. <a name="l01713"></a>01713         S1 = __SSAT(T1 - S1, 16u);
    1717. 

  1717. <a name="l01714"></a>01714 
    1718. 

  1718. <a name="l01715"></a>01715         <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    1719. 

  1719. <a name="l01716"></a>01716         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1720. 

  1720. <a name="l01717"></a>01717         T0 = pSrc16[i1 * 2u];
    1721. 

  1721. <a name="l01718"></a>01718         T1 = pSrc16[(i1 * 2u) + 1u];
    1722. 

  1722. <a name="l01719"></a>01719 
    1723. 

  1723. <a name="l01720"></a>01720         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1724. 

  1724. <a name="l01721"></a>01721         U0 = pSrc16[i3 * 2u];
    1725. 

  1725. <a name="l01722"></a>01722         U1 = pSrc16[(i3 * 2u) + 1u];
    1726. 

  1726. <a name="l01723"></a>01723 
    1727. 

  1727. <a name="l01724"></a>01724         <span class="comment">/* T0 = (yb + yd), T1 = (xb + xd) */</span>
    1728. 

  1728. <a name="l01725"></a>01725         T0 = __SSAT(T0 + U0, 16u);
    1729. 

  1729. <a name="l01726"></a>01726         T1 = __SSAT(T1 + U1, 16u);
    1730. 

  1730. <a name="l01727"></a>01727 
    1731. 

  1731. <a name="l01728"></a>01728         <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    1732. 

  1732. <a name="l01729"></a>01729         <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    1733. 

  1733. <a name="l01730"></a>01730         <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    1734. 

  1734. <a name="l01731"></a>01731         pSrc16[i0 * 2u] = ((R0 &gt;&gt; 1u) + (T0 &gt;&gt; 1u)) &gt;&gt; 1u;
    1735. 

  1735. <a name="l01732"></a>01732         pSrc16[(i0 * 2u) + 1u] = ((R1 &gt;&gt; 1u) + (T1 &gt;&gt; 1u)) &gt;&gt; 1u;
    1736. 

  1736. <a name="l01733"></a>01733 
    1737. 

  1737. <a name="l01734"></a>01734         <span class="comment">/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */</span>
    1738. 

  1738. <a name="l01735"></a>01735         R0 = (R0 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    1739. 

  1739. <a name="l01736"></a>01736         R1 = (R1 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    1740. 

  1740. <a name="l01737"></a>01737 
    1741. 

  1741. <a name="l01738"></a>01738         <span class="comment">/* (ya-yb+yc-yd)* (si2) - (xa-xb+xc-xd)* co2 */</span>
    1742. 

  1742. <a name="l01739"></a>01739         out1 = (short) ((Co2 * R0 - Si2 * R1) &gt;&gt; 16);
    1743. 

  1743. <a name="l01740"></a>01740         <span class="comment">/* (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1744. 

  1744. <a name="l01741"></a>01741         out2 = (short) ((Si2 * R0 + Co2 * R1) &gt;&gt; 16);
    1745. 

  1745. <a name="l01742"></a>01742 
    1746. 

  1746. <a name="l01743"></a>01743         <span class="comment">/*  Reading i0+3fftLen/4 */</span>
    1747. 

  1747. <a name="l01744"></a>01744         <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1748. 

  1748. <a name="l01745"></a>01745         T0 = pSrc16[i1 * 2u];
    1749. 

  1749. <a name="l01746"></a>01746         T1 = pSrc16[(i1 * 2u) + 1u];
    1750. 

  1750. <a name="l01747"></a>01747 
    1751. 

  1751. <a name="l01748"></a>01748         <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    1752. 

  1752. <a name="l01749"></a>01749         <span class="comment">/* xc&#39; = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) */</span>
    1753. 

  1753. <a name="l01750"></a>01750         <span class="comment">/* yc&#39; = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */</span>
    1754. 

  1754. <a name="l01751"></a>01751         pSrc16[i1 * 2u] = out1;
    1755. 

  1755. <a name="l01752"></a>01752         pSrc16[(i1 * 2u) + 1u] = out2;
    1756. 

  1756. <a name="l01753"></a>01753 
    1757. 

  1757. <a name="l01754"></a>01754         <span class="comment">/*  Butterfly calculations */</span>
    1758. 

  1758. <a name="l01755"></a>01755         <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1759. 

  1759. <a name="l01756"></a>01756         U0 = pSrc16[i3 * 2u];
    1760. 

  1760. <a name="l01757"></a>01757         U1 = pSrc16[(i3 * 2u) + 1u];
    1761. 

  1761. <a name="l01758"></a>01758 
    1762. 

  1762. <a name="l01759"></a>01759         <span class="comment">/* T0 = yb-yd, T1 = xb-xd) */</span>
    1763. 

  1763. <a name="l01760"></a>01760         T0 = __SSAT(T0 - U0, 16u);
    1764. 

  1764. <a name="l01761"></a>01761         T1 = __SSAT(T1 - U1, 16u);
    1765. 

  1765. <a name="l01762"></a>01762 
    1766. 

  1766. <a name="l01763"></a>01763         <span class="comment">/* R0 = (ya-yc) - (xb- xd) , R1 = (xa-xc) + (yb-yd) */</span>
    1767. 

  1767. <a name="l01764"></a>01764         R0 = (S0 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    1768. 

  1768. <a name="l01765"></a>01765         R1 = (S1 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    1769. 

  1769. <a name="l01766"></a>01766 
    1770. 

  1770. <a name="l01767"></a>01767         <span class="comment">/* S1 = (ya-yc) + (xb- xd), S1 = (xa-xc) - (yb-yd) */</span>
    1771. 

  1771. <a name="l01768"></a>01768         S0 = (S0 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    1772. 

  1772. <a name="l01769"></a>01769         S1 = (S1 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    1773. 

  1773. <a name="l01770"></a>01770 
    1774. 

  1774. <a name="l01771"></a>01771         <span class="comment">/*  Butterfly process for the i0+fftLen/2 sample */</span>
    1775. 

  1775. <a name="l01772"></a>01772         out1 = (short) ((Co1 * S0 - Si1 * S1) &gt;&gt; 16u);
    1776. 

  1776. <a name="l01773"></a>01773         out2 = (short) ((Si1 * S0 + Co1 * S1) &gt;&gt; 16u);
    1777. 

  1777. <a name="l01774"></a>01774         <span class="comment">/* xb&#39; = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) */</span>
    1778. 

  1778. <a name="l01775"></a>01775         <span class="comment">/* yb&#39; = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */</span>
    1779. 

  1779. <a name="l01776"></a>01776         pSrc16[i2 * 2u] = out1;
    1780. 

  1780. <a name="l01777"></a>01777         pSrc16[(i2 * 2u) + 1u] = out2;
    1781. 

  1781. <a name="l01778"></a>01778 
    1782. 

  1782. <a name="l01779"></a>01779         <span class="comment">/*  Butterfly process for the i0+3fftLen/4 sample */</span>
    1783. 

  1783. <a name="l01780"></a>01780         out1 = (short) ((Co3 * R0 - Si3 * R1) &gt;&gt; 16u);
    1784. 

  1784. <a name="l01781"></a>01781 
    1785. 

  1785. <a name="l01782"></a>01782         out2 = (short) ((Si3 * R0 + Co3 * R1) &gt;&gt; 16u);
    1786. 

  1786. <a name="l01783"></a>01783         <span class="comment">/* xd&#39; = (xa+yb-xc-yd)* Co3 - (ya-xb-yc+xd)* (si3) */</span>
    1787. 

  1787. <a name="l01784"></a>01784         <span class="comment">/* yd&#39; = (ya-xb-yc+xd)* Co3 + (xa+yb-xc-yd)* (si3) */</span>
    1788. 

  1788. <a name="l01785"></a>01785         pSrc16[i3 * 2u] = out1;
    1789. 

  1789. <a name="l01786"></a>01786         pSrc16[(i3 * 2u) + 1u] = out2;
    1790. 

  1790. <a name="l01787"></a>01787 
    1791. 

  1791. <a name="l01788"></a>01788 
    1792. 

  1792. <a name="l01789"></a>01789       }
    1793. 

  1793. <a name="l01790"></a>01790     }
    1794. 

  1794. <a name="l01791"></a>01791     <span class="comment">/*  Twiddle coefficients index modifier */</span>
    1795. 

  1795. <a name="l01792"></a>01792     twidCoefModifier &lt;&lt;= 2u;
    1796. 

  1796. <a name="l01793"></a>01793   }
    1797. 

  1797. <a name="l01794"></a>01794   <span class="comment">/*  End of Middle stages process */</span>
    1798. 

  1798. <a name="l01795"></a>01795 
    1799. 

  1799. <a name="l01796"></a>01796 
    1800. 

  1800. <a name="l01797"></a>01797   <span class="comment">/* data is in 10.6(q6) format for the 1024 point */</span>
    1801. 

  1801. <a name="l01798"></a>01798   <span class="comment">/* data is in 8.8(q8) format for the 256 point   */</span>
    1802. 

  1802. <a name="l01799"></a>01799   <span class="comment">/* data is in 6.10(q10) format for the 64 point  */</span>
    1803. 

  1803. <a name="l01800"></a>01800   <span class="comment">/* data is in 4.12(q12) format for the 16 point  */</span>
    1804. 

  1804. <a name="l01801"></a>01801 
    1805. 

  1805. <a name="l01802"></a>01802   <span class="comment">/* start of last stage process */</span>
    1806. 

  1806. <a name="l01803"></a>01803 
    1807. 

  1807. <a name="l01804"></a>01804 
    1808. 

  1808. <a name="l01805"></a>01805   <span class="comment">/*  Initializations for the last stage */</span>
    1809. 

  1809. <a name="l01806"></a>01806   n1 = n2;
    1810. 

  1810. <a name="l01807"></a>01807   n2 &gt;&gt;= 2u;
    1811. 

  1811. <a name="l01808"></a>01808 
    1812. 

  1812. <a name="l01809"></a>01809   <span class="comment">/*  Butterfly implementation */</span>
    1813. 

  1813. <a name="l01810"></a>01810   <span class="keywordflow">for</span> (i0 = 0u; i0 &lt;= (fftLen - n1); i0 += n1)
    1814. 

  1814. <a name="l01811"></a>01811   {
    1815. 

  1815. <a name="l01812"></a>01812     <span class="comment">/*  index calculation for the input as, */</span>
    1816. 

  1816. <a name="l01813"></a>01813     <span class="comment">/*  pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */</span>
    1817. 

  1817. <a name="l01814"></a>01814     i1 = i0 + n2;
    1818. 

  1818. <a name="l01815"></a>01815     i2 = i1 + n2;
    1819. 

  1819. <a name="l01816"></a>01816     i3 = i2 + n2;
    1820. 

  1820. <a name="l01817"></a>01817 
    1821. 

  1821. <a name="l01818"></a>01818     <span class="comment">/*  Reading i0, i0+fftLen/2 inputs */</span>
    1822. 

  1822. <a name="l01819"></a>01819     <span class="comment">/* Read ya (real), xa(imag) input */</span>
    1823. 

  1823. <a name="l01820"></a>01820     T0 = pSrc16[i0 * 2u];
    1824. 

  1824. <a name="l01821"></a>01821     T1 = pSrc16[(i0 * 2u) + 1u];
    1825. 

  1825. <a name="l01822"></a>01822     <span class="comment">/* Read yc (real), xc(imag) input */</span>
    1826. 

  1826. <a name="l01823"></a>01823     S0 = pSrc16[i2 * 2u];
    1827. 

  1827. <a name="l01824"></a>01824     S1 = pSrc16[(i2 * 2u) + 1u];
    1828. 

  1828. <a name="l01825"></a>01825 
    1829. 

  1829. <a name="l01826"></a>01826     <span class="comment">/* R0 = (ya + yc), R1 = (xa + xc) */</span>
    1830. 

  1830. <a name="l01827"></a>01827     R0 = __SSAT(T0 + S0, 16u);
    1831. 

  1831. <a name="l01828"></a>01828     R1 = __SSAT(T1 + S1, 16u);
    1832. 

  1832. <a name="l01829"></a>01829     <span class="comment">/* S0 = (ya - yc), S1 = (xa - xc) */</span>
    1833. 

  1833. <a name="l01830"></a>01830     S0 = __SSAT(T0 - S0, 16u);
    1834. 

  1834. <a name="l01831"></a>01831     S1 = __SSAT(T1 - S1, 16u);
    1835. 

  1835. <a name="l01832"></a>01832 
    1836. 

  1836. <a name="l01833"></a>01833     <span class="comment">/*  Reading i0+fftLen/4 , i0+3fftLen/4 inputs */</span>
    1837. 

  1837. <a name="l01834"></a>01834     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1838. 

  1838. <a name="l01835"></a>01835     T0 = pSrc16[i1 * 2u];
    1839. 

  1839. <a name="l01836"></a>01836     T1 = pSrc16[(i1 * 2u) + 1u];
    1840. 

  1840. <a name="l01837"></a>01837     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1841. 

  1841. <a name="l01838"></a>01838     U0 = pSrc16[i3 * 2u];
    1842. 

  1842. <a name="l01839"></a>01839     U1 = pSrc16[(i3 * 2u) + 1u];
    1843. 

  1843. <a name="l01840"></a>01840 
    1844. 

  1844. <a name="l01841"></a>01841     <span class="comment">/* T0 = (yb + yd), T1 = (xb + xd) */</span>
    1845. 

  1845. <a name="l01842"></a>01842     T0 = __SSAT(T0 + U0, 16u);
    1846. 

  1846. <a name="l01843"></a>01843     T1 = __SSAT(T1 + U1, 16u);
    1847. 

  1847. <a name="l01844"></a>01844 
    1848. 

  1848. <a name="l01845"></a>01845     <span class="comment">/*  writing the butterfly processed i0 sample */</span>
    1849. 

  1849. <a name="l01846"></a>01846     <span class="comment">/* xa&#39; = xa + xb + xc + xd */</span>
    1850. 

  1850. <a name="l01847"></a>01847     <span class="comment">/* ya&#39; = ya + yb + yc + yd */</span>
    1851. 

  1851. <a name="l01848"></a>01848     pSrc16[i0 * 2u] = (R0 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    1852. 

  1852. <a name="l01849"></a>01849     pSrc16[(i0 * 2u) + 1u] = (R1 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    1853. 

  1853. <a name="l01850"></a>01850 
    1854. 

  1854. <a name="l01851"></a>01851     <span class="comment">/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */</span>
    1855. 

  1855. <a name="l01852"></a>01852     R0 = (R0 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    1856. 

  1856. <a name="l01853"></a>01853     R1 = (R1 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    1857. 

  1857. <a name="l01854"></a>01854 
    1858. 

  1858. <a name="l01855"></a>01855     <span class="comment">/* Read yb (real), xb(imag) input */</span>
    1859. 

  1859. <a name="l01856"></a>01856     T0 = pSrc16[i1 * 2u];
    1860. 

  1860. <a name="l01857"></a>01857     T1 = pSrc16[(i1 * 2u) + 1u];
    1861. 

  1861. <a name="l01858"></a>01858 
    1862. 

  1862. <a name="l01859"></a>01859     <span class="comment">/*  writing the butterfly processed i0 + fftLen/4 sample */</span>
    1863. 

  1863. <a name="l01860"></a>01860     <span class="comment">/* xc&#39; = (xa-xb+xc-xd) */</span>
    1864. 

  1864. <a name="l01861"></a>01861     <span class="comment">/* yc&#39; = (ya-yb+yc-yd) */</span>
    1865. 

  1865. <a name="l01862"></a>01862     pSrc16[i1 * 2u] = R0;
    1866. 

  1866. <a name="l01863"></a>01863     pSrc16[(i1 * 2u) + 1u] = R1;
    1867. 

  1867. <a name="l01864"></a>01864 
    1868. 

  1868. <a name="l01865"></a>01865     <span class="comment">/* Read yd (real), xd(imag) input */</span>
    1869. 

  1869. <a name="l01866"></a>01866     U0 = pSrc16[i3 * 2u];
    1870. 

  1870. <a name="l01867"></a>01867     U1 = pSrc16[(i3 * 2u) + 1u];
    1871. 

  1871. <a name="l01868"></a>01868     <span class="comment">/* T0 = (yb - yd), T1 = (xb - xd) */</span>
    1872. 

  1872. <a name="l01869"></a>01869     T0 = __SSAT(T0 - U0, 16u);
    1873. 

  1873. <a name="l01870"></a>01870     T1 = __SSAT(T1 - U1, 16u);
    1874. 

  1874. <a name="l01871"></a>01871 
    1875. 

  1875. <a name="l01872"></a>01872     <span class="comment">/*  writing the butterfly processed i0 + fftLen/2 sample */</span>
    1876. 

  1876. <a name="l01873"></a>01873     <span class="comment">/* xb&#39; = (xa-yb-xc+yd) */</span>
    1877. 

  1877. <a name="l01874"></a>01874     <span class="comment">/* yb&#39; = (ya+xb-yc-xd) */</span>
    1878. 

  1878. <a name="l01875"></a>01875     pSrc16[i2 * 2u] = (S0 &gt;&gt; 1u) - (T1 &gt;&gt; 1u);
    1879. 

  1879. <a name="l01876"></a>01876     pSrc16[(i2 * 2u) + 1u] = (S1 &gt;&gt; 1u) + (T0 &gt;&gt; 1u);
    1880. 

  1880. <a name="l01877"></a>01877 
    1881. 

  1881. <a name="l01878"></a>01878 
    1882. 

  1882. <a name="l01879"></a>01879     <span class="comment">/*  writing the butterfly processed i0 + 3fftLen/4 sample */</span>
    1883. 

  1883. <a name="l01880"></a>01880     <span class="comment">/* xd&#39; = (xa+yb-xc-yd) */</span>
    1884. 

  1884. <a name="l01881"></a>01881     <span class="comment">/* yd&#39; = (ya-xb-yc+xd) */</span>
    1885. 

  1885. <a name="l01882"></a>01882     pSrc16[i3 * 2u] = (S0 &gt;&gt; 1u) + (T1 &gt;&gt; 1u);
    1886. 

  1886. <a name="l01883"></a>01883     pSrc16[(i3 * 2u) + 1u] = (S1 &gt;&gt; 1u) - (T0 &gt;&gt; 1u);
    1887. 

  1887. <a name="l01884"></a>01884   }
    1888. 

  1888. <a name="l01885"></a>01885   <span class="comment">/* end of last stage  process */</span>
    1889. 

  1889. <a name="l01886"></a>01886 
    1890. 

  1890. <a name="l01887"></a>01887   <span class="comment">/* output is in 11.5(q5) format for the 1024 point */</span>
    1891. 

  1891. <a name="l01888"></a>01888   <span class="comment">/* output is in 9.7(q7) format for the 256 point   */</span>
    1892. 

  1892. <a name="l01889"></a>01889   <span class="comment">/* output is in 7.9(q9) format for the 64 point  */</span>
    1893. 

  1893. <a name="l01890"></a>01890   <span class="comment">/* output is in 5.11(q11) format for the 16 point  */</span>
    1894. 

  1894. <a name="l01891"></a>01891 
    1895. 

  1895. <a name="l01892"></a>01892 <span class="preprocessor">#endif </span><span class="comment">/* #ifndef ARM_MATH_CM0 */</span>
    1896. 

  1896. <a name="l01893"></a>01893 
    1897. 

  1897. <a name="l01894"></a>01894 }
    1898. 

  1898. <a name="l01895"></a>01895 
    1899. 

  1899. <a name="l01896"></a>01896 
    1900. 

  1900. <a name="l01897"></a>01897 <span class="comment">/*   </span>
    1901. 

  1901. <a name="l01898"></a>01898 <span class="comment">   * @brief  In-place bit reversal function.  </span>
    1902. 

  1902. <a name="l01899"></a>01899 <span class="comment">   * @param[in, out] *pSrc        points to the in-place buffer of Q15 data type.  </span>
    1903. 

  1903. <a name="l01900"></a>01900 <span class="comment">   * @param[in]      fftLen       length of the FFT.  </span>
    1904. 

  1904. <a name="l01901"></a>01901 <span class="comment">   * @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table  </span>
    1905. 

  1905. <a name="l01902"></a>01902 <span class="comment">   * @param[in]      *pBitRevTab  points to bit reversal table.  </span>
    1906. 

  1906. <a name="l01903"></a>01903 <span class="comment">   * @return none.  </span>
    1907. 

  1907. <a name="l01904"></a>01904 <span class="comment"> */</span>
    1908. 

  1908. <a name="l01905"></a>01905 
    1909. 

  1909. <a name="l01906"></a><a class="code" href="arm__math_8h.html#a73f48eaea9297605705ae25d3405343e">01906</a> <span class="keywordtype">void</span> <a class="code" href="arm__cfft__radix4__q15_8c.html#a12a07b49948c354172ae07358309a4a5" title="In-place bit reversal function.">arm_bitreversal_q15</a>(
    1910. 

  1910. <a name="l01907"></a>01907   <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pSrc16,
    1911. 

  1911. <a name="l01908"></a>01908   uint32_t fftLen,
    1912. 

  1912. <a name="l01909"></a>01909   uint16_t bitRevFactor,
    1913. 

  1913. <a name="l01910"></a>01910   uint16_t * pBitRevTab)
    1914. 

  1914. <a name="l01911"></a>01911 {
    1915. 

  1915. <a name="l01912"></a>01912   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *pSrc = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *) pSrc16;
    1916. 

  1916. <a name="l01913"></a>01913   <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> in;
    1917. 

  1917. <a name="l01914"></a>01914   uint32_t fftLenBy2, fftLenBy2p1;
    1918. 

  1918. <a name="l01915"></a>01915   uint32_t i, j;
    1919. 

  1919. <a name="l01916"></a>01916 
    1920. 

  1920. <a name="l01917"></a>01917   <span class="comment">/*  Initializations */</span>
    1921. 

  1921. <a name="l01918"></a>01918   j = 0u;
    1922. 

  1922. <a name="l01919"></a>01919   fftLenBy2 = fftLen / 2u;
    1923. 

  1923. <a name="l01920"></a>01920   fftLenBy2p1 = (fftLen / 2u) + 1u;
    1924. 

  1924. <a name="l01921"></a>01921 
    1925. 

  1925. <a name="l01922"></a>01922   <span class="comment">/* Bit Reversal Implementation */</span>
    1926. 

  1926. <a name="l01923"></a>01923   <span class="keywordflow">for</span> (i = 0u; i &lt;= (fftLenBy2 - 2u); i += 2u)
    1927. 

  1927. <a name="l01924"></a>01924   {
    1928. 

  1928. <a name="l01925"></a>01925     <span class="keywordflow">if</span>(i &lt; j)
    1929. 

  1929. <a name="l01926"></a>01926     {
    1930. 

  1930. <a name="l01927"></a>01927       <span class="comment">/*  pSrc[i] &lt;-&gt; pSrc[j]; */</span>
    1931. 

  1931. <a name="l01928"></a>01928       <span class="comment">/*  pSrc[i+1u] &lt;-&gt; pSrc[j+1u] */</span>
    1932. 

  1932. <a name="l01929"></a>01929       in = pSrc[i];
    1933. 

  1933. <a name="l01930"></a>01930       pSrc[i] = pSrc[j];
    1934. 

  1934. <a name="l01931"></a>01931       pSrc[j] = in;
    1935. 

  1935. <a name="l01932"></a>01932 
    1936. 

  1936. <a name="l01933"></a>01933       <span class="comment">/*  pSrc[i + fftLenBy2p1] &lt;-&gt; pSrc[j + fftLenBy2p1];  */</span>
    1937. 

  1937. <a name="l01934"></a>01934       <span class="comment">/*  pSrc[i + fftLenBy2p1+1u] &lt;-&gt; pSrc[j + fftLenBy2p1+1u] */</span>
    1938. 

  1938. <a name="l01935"></a>01935       in = pSrc[i + fftLenBy2p1];
    1939. 

  1939. <a name="l01936"></a>01936       pSrc[i + fftLenBy2p1] = pSrc[j + fftLenBy2p1];
    1940. 

  1940. <a name="l01937"></a>01937       pSrc[j + fftLenBy2p1] = in;
    1941. 

  1941. <a name="l01938"></a>01938     }
    1942. 

  1942. <a name="l01939"></a>01939 
    1943. 

  1943. <a name="l01940"></a>01940     <span class="comment">/*  pSrc[i+1u] &lt;-&gt; pSrc[j+fftLenBy2];         */</span>
    1944. 

  1944. <a name="l01941"></a>01941     <span class="comment">/*  pSrc[i+2] &lt;-&gt; pSrc[j+fftLenBy2+1u]  */</span>
    1945. 

  1945. <a name="l01942"></a>01942     in = pSrc[i + 1u];
    1946. 

  1946. <a name="l01943"></a>01943     pSrc[i + 1u] = pSrc[j + fftLenBy2];
    1947. 

  1947. <a name="l01944"></a>01944     pSrc[j + fftLenBy2] = in;
    1948. 

  1948. <a name="l01945"></a>01945 
    1949. 

  1949. <a name="l01946"></a>01946     <span class="comment">/*  Reading the index for the bit reversal */</span>
    1950. 

  1950. <a name="l01947"></a>01947     j = *pBitRevTab;
    1951. 

  1951. <a name="l01948"></a>01948 
    1952. 

  1952. <a name="l01949"></a>01949     <span class="comment">/*  Updating the bit reversal index depending on the fft length  */</span>
    1953. 

  1953. <a name="l01950"></a>01950     pBitRevTab += bitRevFactor;
    1954. 

  1954. <a name="l01951"></a>01951   }
    1955. 

  1955. <a name="l01952"></a>01952 }
    1956. 

  1956. </pre></div></div>
    1957. 

  1957. </div>
    1958. 

  1958. <!--- window showing the filter options -->
    1959. 

  1959. <div id="MSearchSelectWindow"
    1960. 

  1960.      onmouseover="return searchBox.OnSearchSelectShow()"
    1961. 

  1961.      onmouseout="return searchBox.OnSearchSelectHide()"
    1962. 

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