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49 <div class="headertitle">
50 <h1>arm_cfft_radix4_q31.c</h1> </div>
52 <div class="contents">
53 <a href="arm__cfft__radix4__q31_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 <a name="l00002"></a>00002 <span class="comment">* Copyright (C) 2010 ARM Limited. All rights reserved. </span>
55 <a name="l00003"></a>00003 <span class="comment">* </span>
56 <a name="l00004"></a>00004 <span class="comment">* $Date: 15. July 2011 </span>
57 <a name="l00005"></a>00005 <span class="comment">* $Revision: V1.0.10 </span>
58 <a name="l00006"></a>00006 <span class="comment">* </span>
59 <a name="l00007"></a>00007 <span class="comment">* Project: CMSIS DSP Library </span>
60 <a name="l00008"></a>00008 <span class="comment">* Title: arm_cfft_radix4_q31.c </span>
61 <a name="l00009"></a>00009 <span class="comment">* </span>
62 <a name="l00010"></a>00010 <span class="comment">* Description: This file has function definition of Radix-4 FFT & IFFT function and </span>
63 <a name="l00011"></a>00011 <span class="comment">* In-place bit reversal using bit reversal table </span>
64 <a name="l00012"></a>00012 <span class="comment">* </span>
65 <a name="l00013"></a>00013 <span class="comment">* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0</span>
66 <a name="l00014"></a>00014 <span class="comment">* </span>
67 <a name="l00015"></a>00015 <span class="comment">* Version 1.0.10 2011/7/15 </span>
68 <a name="l00016"></a>00016 <span class="comment">* Big Endian support added and Merged M0 and M3/M4 Source code. </span>
69 <a name="l00017"></a>00017 <span class="comment">* </span>
70 <a name="l00018"></a>00018 <span class="comment">* Version 1.0.3 2010/11/29 </span>
71 <a name="l00019"></a>00019 <span class="comment">* Re-organized the CMSIS folders and updated documentation. </span>
72 <a name="l00020"></a>00020 <span class="comment">* </span>
73 <a name="l00021"></a>00021 <span class="comment">* Version 1.0.2 2010/11/11 </span>
74 <a name="l00022"></a>00022 <span class="comment">* Documentation updated. </span>
75 <a name="l00023"></a>00023 <span class="comment">* </span>
76 <a name="l00024"></a>00024 <span class="comment">* Version 1.0.1 2010/10/05 </span>
77 <a name="l00025"></a>00025 <span class="comment">* Production release and review comments incorporated. </span>
78 <a name="l00026"></a>00026 <span class="comment">* </span>
79 <a name="l00027"></a>00027 <span class="comment">* Version 1.0.0 2010/09/20 </span>
80 <a name="l00028"></a>00028 <span class="comment">* Production release and review comments incorporated. </span>
81 <a name="l00029"></a>00029 <span class="comment">* </span>
82 <a name="l00030"></a>00030 <span class="comment">* Version 0.0.5 2010/04/26 </span>
83 <a name="l00031"></a>00031 <span class="comment">* incorporated review comments and updated with latest CMSIS layer </span>
84 <a name="l00032"></a>00032 <span class="comment">* </span>
85 <a name="l00033"></a>00033 <span class="comment">* Version 0.0.3 2010/03/10 </span>
86 <a name="l00034"></a>00034 <span class="comment">* Initial version </span>
87 <a name="l00035"></a>00035 <span class="comment">* -------------------------------------------------------------------- */</span>
88 <a name="l00036"></a>00036 <span class="preprocessor">#include "<a class="code" href="arm__math_8h.html">arm_math.h</a>"</span>
89 <a name="l00037"></a>00037
90 <a name="l00038"></a>00038
91 <a name="l00066"></a><a class="code" href="group___c_f_f_t___c_i_f_f_t.html#gafde3ee1f58cf393b45a9073174fff548">00066</a> <span class="keywordtype">void</span> <a class="code" href="group___c_f_f_t___c_i_f_f_t.html#gafde3ee1f58cf393b45a9073174fff548" title="Processing function for the Q31 CFFT/CIFFT.">arm_cfft_radix4_q31</a>(
92 <a name="l00067"></a>00067 <span class="keyword">const</span> <a class="code" href="structarm__cfft__radix4__instance__q31.html" title="Instance structure for the Q31 CFFT/CIFFT function.">arm_cfft_radix4_instance_q31</a> * S,
93 <a name="l00068"></a>00068 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> * pSrc)
94 <a name="l00069"></a>00069 {
95 <a name="l00070"></a>00070 <span class="keywordflow">if</span>(S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#adc0a62ba669ad2282ecbe43d5d96abab">ifftFlag</a> == 1u)
96 <a name="l00071"></a>00071 {
97 <a name="l00072"></a>00072 <span class="comment">/* Complex IFFT radix-4 */</span>
98 <a name="l00073"></a>00073 <a class="code" href="arm__cfft__radix4__q31_8c.html#ac9c7c553114c1201a3a987a11b8a6d01" title="Core function for the Q31 CIFFT butterfly process.">arm_radix4_butterfly_inverse_q31</a>(pSrc, S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#ab413d2a5d3f45fa187d93813bf3bf81b">fftLen</a>, S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#a561c22dee4cbdcfa0fd5f15106ecc306">pTwiddle</a>,
99 <a name="l00074"></a>00074 S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#a8cf8187b8232815cf17ee82bf572ecf9">twidCoefModifier</a>);
100 <a name="l00075"></a>00075 }
101 <a name="l00076"></a>00076 <span class="keywordflow">else</span>
102 <a name="l00077"></a>00077 {
103 <a name="l00078"></a>00078 <span class="comment">/* Complex FFT radix-4 */</span>
104 <a name="l00079"></a>00079 <a class="code" href="arm__cfft__radix4__q31_8c.html#ac12f1e7f159d5741358cdc36830a0395" title="Core function for the Q31 CFFT butterfly process.">arm_radix4_butterfly_q31</a>(pSrc, S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#ab413d2a5d3f45fa187d93813bf3bf81b">fftLen</a>, S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#a561c22dee4cbdcfa0fd5f15106ecc306">pTwiddle</a>,
105 <a name="l00080"></a>00080 S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#a8cf8187b8232815cf17ee82bf572ecf9">twidCoefModifier</a>);
106 <a name="l00081"></a>00081 }
107 <a name="l00082"></a>00082
108 <a name="l00083"></a>00083
109 <a name="l00084"></a>00084 <span class="keywordflow">if</span>(S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#a5a7c4f4c7b3fb655cbb2bc11ef160a2a">bitReverseFlag</a> == 1u)
110 <a name="l00085"></a>00085 {
111 <a name="l00086"></a>00086 <span class="comment">/* Bit Reversal */</span>
112 <a name="l00087"></a>00087 <a class="code" href="arm__cfft__radix4__q31_8c.html#a27618705158b5c42db5fb0a381f8efc1" title="In-place bit reversal function.">arm_bitreversal_q31</a>(pSrc, S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#ab413d2a5d3f45fa187d93813bf3bf81b">fftLen</a>, S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#a94d2fead4efa4d5eaae142bbe30b0e15">bitRevFactor</a>, S-><a class="code" href="structarm__cfft__radix4__instance__q31.html#a33a3bc774c97373261699463c05dfe54">pBitRevTable</a>);
113 <a name="l00088"></a>00088 }
114 <a name="l00089"></a>00089
115 <a name="l00090"></a>00090 }
116 <a name="l00091"></a>00091
117 <a name="l00096"></a>00096 <span class="comment">/* </span>
118 <a name="l00097"></a>00097 <span class="comment">* Radix-4 FFT algorithm used is : </span>
119 <a name="l00098"></a>00098 <span class="comment">* </span>
120 <a name="l00099"></a>00099 <span class="comment">* Input real and imaginary data: </span>
121 <a name="l00100"></a>00100 <span class="comment">* x(n) = xa + j * ya </span>
122 <a name="l00101"></a>00101 <span class="comment">* x(n+N/4 ) = xb + j * yb </span>
123 <a name="l00102"></a>00102 <span class="comment">* x(n+N/2 ) = xc + j * yc </span>
124 <a name="l00103"></a>00103 <span class="comment">* x(n+3N 4) = xd + j * yd </span>
125 <a name="l00104"></a>00104 <span class="comment">* </span>
126 <a name="l00105"></a>00105 <span class="comment">* </span>
127 <a name="l00106"></a>00106 <span class="comment">* Output real and imaginary data: </span>
128 <a name="l00107"></a>00107 <span class="comment">* x(4r) = xa'+ j * ya' </span>
129 <a name="l00108"></a>00108 <span class="comment">* x(4r+1) = xb'+ j * yb' </span>
130 <a name="l00109"></a>00109 <span class="comment">* x(4r+2) = xc'+ j * yc' </span>
131 <a name="l00110"></a>00110 <span class="comment">* x(4r+3) = xd'+ j * yd' </span>
132 <a name="l00111"></a>00111 <span class="comment">* </span>
133 <a name="l00112"></a>00112 <span class="comment">* </span>
134 <a name="l00113"></a>00113 <span class="comment">* Twiddle factors for radix-4 FFT: </span>
135 <a name="l00114"></a>00114 <span class="comment">* Wn = co1 + j * (- si1) </span>
136 <a name="l00115"></a>00115 <span class="comment">* W2n = co2 + j * (- si2) </span>
137 <a name="l00116"></a>00116 <span class="comment">* W3n = co3 + j * (- si3) </span>
138 <a name="l00117"></a>00117 <span class="comment">* </span>
139 <a name="l00118"></a>00118 <span class="comment">* Butterfly implementation: </span>
140 <a name="l00119"></a>00119 <span class="comment">* xa' = xa + xb + xc + xd </span>
141 <a name="l00120"></a>00120 <span class="comment">* ya' = ya + yb + yc + yd </span>
142 <a name="l00121"></a>00121 <span class="comment">* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) </span>
143 <a name="l00122"></a>00122 <span class="comment">* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) </span>
144 <a name="l00123"></a>00123 <span class="comment">* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) </span>
145 <a name="l00124"></a>00124 <span class="comment">* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) </span>
146 <a name="l00125"></a>00125 <span class="comment">* xd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) </span>
147 <a name="l00126"></a>00126 <span class="comment">* yd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) </span>
148 <a name="l00127"></a>00127 <span class="comment">* </span>
149 <a name="l00128"></a>00128 <span class="comment">*/</span>
150 <a name="l00129"></a>00129
151 <a name="l00139"></a><a class="code" href="arm__math_8h.html#ac12f1e7f159d5741358cdc36830a0395">00139</a> <span class="keywordtype">void</span> <a class="code" href="arm__cfft__radix4__q31_8c.html#ac12f1e7f159d5741358cdc36830a0395" title="Core function for the Q31 CFFT butterfly process.">arm_radix4_butterfly_q31</a>(
152 <a name="l00140"></a>00140 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> * pSrc,
153 <a name="l00141"></a>00141 uint32_t fftLen,
154 <a name="l00142"></a>00142 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> * pCoef,
155 <a name="l00143"></a>00143 uint32_t twidCoefModifier)
156 <a name="l00144"></a>00144 {
157 <a name="l00145"></a>00145 uint32_t n1, n2, ia1, ia2, ia3, i0, i1, i2, i3, j, k;
158 <a name="l00146"></a>00146 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> t1, t2, r1, r2, s1, s2, co1, co2, co3, si1, si2, si3;
159 <a name="l00147"></a>00147
160 <a name="l00148"></a>00148
161 <a name="l00149"></a>00149 <span class="comment">/* Total process is divided into three stages */</span>
162 <a name="l00150"></a>00150
163 <a name="l00151"></a>00151 <span class="comment">/* process first stage, middle stages, & last stage */</span>
164 <a name="l00152"></a>00152
165 <a name="l00153"></a>00153
166 <a name="l00154"></a>00154 <span class="comment">/* start of first stage process */</span>
167 <a name="l00155"></a>00155
168 <a name="l00156"></a>00156 <span class="comment">/* Initializations for the first stage */</span>
169 <a name="l00157"></a>00157 n2 = fftLen;
170 <a name="l00158"></a>00158 n1 = n2;
171 <a name="l00159"></a>00159 <span class="comment">/* n2 = fftLen/4 */</span>
172 <a name="l00160"></a>00160 n2 >>= 2u;
173 <a name="l00161"></a>00161 i0 = 0u;
174 <a name="l00162"></a>00162 ia1 = 0u;
175 <a name="l00163"></a>00163
176 <a name="l00164"></a>00164 j = n2;
177 <a name="l00165"></a>00165
178 <a name="l00166"></a>00166 <span class="comment">/* Calculation of first stage */</span>
179 <a name="l00167"></a>00167 <span class="keywordflow">do</span>
180 <a name="l00168"></a>00168 {
181 <a name="l00169"></a>00169 <span class="comment">/* index calculation for the input as, */</span>
182 <a name="l00170"></a>00170 <span class="comment">/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2u], pSrc[i0 + 3fftLen/4] */</span>
183 <a name="l00171"></a>00171 i1 = i0 + n2;
184 <a name="l00172"></a>00172 i2 = i1 + n2;
185 <a name="l00173"></a>00173 i3 = i2 + n2;
186 <a name="l00174"></a>00174
187 <a name="l00175"></a>00175 <span class="comment">/* input is in 1.31(q31) format and provide 4 guard bits for the input */</span>
188 <a name="l00176"></a>00176
189 <a name="l00177"></a>00177 <span class="comment">/* Butterfly implementation */</span>
190 <a name="l00178"></a>00178 <span class="comment">/* xa + xc */</span>
191 <a name="l00179"></a>00179 r1 = (pSrc[(2u * i0)] >> 4u) + (pSrc[(2u * i2)] >> 4u);
192 <a name="l00180"></a>00180 <span class="comment">/* xa - xc */</span>
193 <a name="l00181"></a>00181 r2 = (pSrc[2u * i0] >> 4u) - (pSrc[2u * i2] >> 4u);
194 <a name="l00182"></a>00182
195 <a name="l00183"></a>00183 <span class="comment">/* ya + yc */</span>
196 <a name="l00184"></a>00184 s1 = (pSrc[(2u * i0) + 1u] >> 4u) + (pSrc[(2u * i2) + 1u] >> 4u);
197 <a name="l00185"></a>00185 <span class="comment">/* ya - yc */</span>
198 <a name="l00186"></a>00186 s2 = (pSrc[(2u * i0) + 1u] >> 4u) - (pSrc[(2u * i2) + 1u] >> 4u);
199 <a name="l00187"></a>00187
200 <a name="l00188"></a>00188 <span class="comment">/* xb + xd */</span>
201 <a name="l00189"></a>00189 t1 = (pSrc[2u * i1] >> 4u) + (pSrc[2u * i3] >> 4u);
202 <a name="l00190"></a>00190
203 <a name="l00191"></a>00191 <span class="comment">/* xa' = xa + xb + xc + xd */</span>
204 <a name="l00192"></a>00192 pSrc[2u * i0] = (r1 + t1);
205 <a name="l00193"></a>00193 <span class="comment">/* (xa + xc) - (xb + xd) */</span>
206 <a name="l00194"></a>00194 r1 = r1 - t1;
207 <a name="l00195"></a>00195 <span class="comment">/* yb + yd */</span>
208 <a name="l00196"></a>00196 t2 = (pSrc[(2u * i1) + 1u] >> 4u) + (pSrc[(2u * i3) + 1u] >> 4u);
209 <a name="l00197"></a>00197 <span class="comment">/* ya' = ya + yb + yc + yd */</span>
210 <a name="l00198"></a>00198 pSrc[(2u * i0) + 1u] = (s1 + t2);
211 <a name="l00199"></a>00199
212 <a name="l00200"></a>00200 <span class="comment">/* (ya + yc) - (yb + yd) */</span>
213 <a name="l00201"></a>00201 s1 = s1 - t2;
214 <a name="l00202"></a>00202
215 <a name="l00203"></a>00203 <span class="comment">/* yb - yd */</span>
216 <a name="l00204"></a>00204 t1 = (pSrc[(2u * i1) + 1u] >> 4u) - (pSrc[(2u * i3) + 1u] >> 4u);
217 <a name="l00205"></a>00205 <span class="comment">/* xb - xd */</span>
218 <a name="l00206"></a>00206 t2 = (pSrc[2u * i1] >> 4u) - (pSrc[2u * i3] >> 4u);
219 <a name="l00207"></a>00207
220 <a name="l00208"></a>00208 <span class="comment">/* index calculation for the coefficients */</span>
221 <a name="l00209"></a>00209 ia2 = 2u * ia1;
222 <a name="l00210"></a>00210 co2 = pCoef[ia2 * 2u];
223 <a name="l00211"></a>00211 si2 = pCoef[(ia2 * 2u) + 1u];
224 <a name="l00212"></a>00212
225 <a name="l00213"></a>00213 <span class="comment">/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */</span>
226 <a name="l00214"></a>00214 pSrc[2u * i1] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co2) >> 32)) +
227 <a name="l00215"></a>00215 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si2) >> 32))) << 1u;
228 <a name="l00216"></a>00216
229 <a name="l00217"></a>00217 <span class="comment">/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */</span>
230 <a name="l00218"></a>00218 pSrc[(2u * i1) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co2) >> 32)) -
231 <a name="l00219"></a>00219 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si2) >> 32))) << 1u;
232 <a name="l00220"></a>00220
233 <a name="l00221"></a>00221 <span class="comment">/* (xa - xc) + (yb - yd) */</span>
234 <a name="l00222"></a>00222 r1 = r2 + t1;
235 <a name="l00223"></a>00223 <span class="comment">/* (xa - xc) - (yb - yd) */</span>
236 <a name="l00224"></a>00224 r2 = r2 - t1;
237 <a name="l00225"></a>00225
238 <a name="l00226"></a>00226 <span class="comment">/* (ya - yc) - (xb - xd) */</span>
239 <a name="l00227"></a>00227 s1 = s2 - t2;
240 <a name="l00228"></a>00228 <span class="comment">/* (ya - yc) + (xb - xd) */</span>
241 <a name="l00229"></a>00229 s2 = s2 + t2;
242 <a name="l00230"></a>00230
243 <a name="l00231"></a>00231 co1 = pCoef[ia1 * 2u];
244 <a name="l00232"></a>00232 si1 = pCoef[(ia1 * 2u) + 1u];
245 <a name="l00233"></a>00233
246 <a name="l00234"></a>00234 <span class="comment">/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */</span>
247 <a name="l00235"></a>00235 pSrc[2u * i2] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co1) >> 32)) +
248 <a name="l00236"></a>00236 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si1) >> 32))) << 1u;
249 <a name="l00237"></a>00237
250 <a name="l00238"></a>00238 <span class="comment">/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */</span>
251 <a name="l00239"></a>00239 pSrc[(2u * i2) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co1) >> 32)) -
252 <a name="l00240"></a>00240 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si1) >> 32))) << 1u;
253 <a name="l00241"></a>00241
254 <a name="l00242"></a>00242 <span class="comment">/* index calculation for the coefficients */</span>
255 <a name="l00243"></a>00243 ia3 = 3u * ia1;
256 <a name="l00244"></a>00244 co3 = pCoef[ia3 * 2u];
257 <a name="l00245"></a>00245 si3 = pCoef[(ia3 * 2u) + 1u];
258 <a name="l00246"></a>00246
259 <a name="l00247"></a>00247 <span class="comment">/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */</span>
260 <a name="l00248"></a>00248 pSrc[2u * i3] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * co3) >> 32)) +
261 <a name="l00249"></a>00249 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * si3) >> 32))) << 1u;
262 <a name="l00250"></a>00250
263 <a name="l00251"></a>00251 <span class="comment">/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */</span>
264 <a name="l00252"></a>00252 pSrc[(2u * i3) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * co3) >> 32)) -
265 <a name="l00253"></a>00253 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * si3) >> 32))) << 1u;
266 <a name="l00254"></a>00254
267 <a name="l00255"></a>00255 <span class="comment">/* Twiddle coefficients index modifier */</span>
268 <a name="l00256"></a>00256 ia1 = ia1 + twidCoefModifier;
269 <a name="l00257"></a>00257
270 <a name="l00258"></a>00258 <span class="comment">/* Updating input index */</span>
271 <a name="l00259"></a>00259 i0 = i0 + 1u;
272 <a name="l00260"></a>00260
273 <a name="l00261"></a>00261 } <span class="keywordflow">while</span>(--j);
274 <a name="l00262"></a>00262
275 <a name="l00263"></a>00263 <span class="comment">/* end of first stage process */</span>
276 <a name="l00264"></a>00264
277 <a name="l00265"></a>00265 <span class="comment">/* data is in 5.27(q27) format */</span>
278 <a name="l00266"></a>00266
279 <a name="l00267"></a>00267
280 <a name="l00268"></a>00268 <span class="comment">/* start of Middle stages process */</span>
281 <a name="l00269"></a>00269
282 <a name="l00270"></a>00270
283 <a name="l00271"></a>00271 <span class="comment">/* each stage in middle stages provides two down scaling of the input */</span>
284 <a name="l00272"></a>00272
285 <a name="l00273"></a>00273 twidCoefModifier <<= 2u;
286 <a name="l00274"></a>00274
287 <a name="l00275"></a>00275
288 <a name="l00276"></a>00276 <span class="keywordflow">for</span> (k = fftLen / 4u; k > 4u; k >>= 2u)
289 <a name="l00277"></a>00277 {
290 <a name="l00278"></a>00278 <span class="comment">/* Initializations for the first stage */</span>
291 <a name="l00279"></a>00279 n1 = n2;
292 <a name="l00280"></a>00280 n2 >>= 2u;
293 <a name="l00281"></a>00281 ia1 = 0u;
294 <a name="l00282"></a>00282
295 <a name="l00283"></a>00283 <span class="comment">/* Calculation of first stage */</span>
296 <a name="l00284"></a>00284 <span class="keywordflow">for</span> (j = 0u; j <= (n2 - 1u); j++)
297 <a name="l00285"></a>00285 {
298 <a name="l00286"></a>00286 <span class="comment">/* index calculation for the coefficients */</span>
299 <a name="l00287"></a>00287 ia2 = ia1 + ia1;
300 <a name="l00288"></a>00288 ia3 = ia2 + ia1;
301 <a name="l00289"></a>00289 co1 = pCoef[ia1 * 2u];
302 <a name="l00290"></a>00290 si1 = pCoef[(ia1 * 2u) + 1u];
303 <a name="l00291"></a>00291 co2 = pCoef[ia2 * 2u];
304 <a name="l00292"></a>00292 si2 = pCoef[(ia2 * 2u) + 1u];
305 <a name="l00293"></a>00293 co3 = pCoef[ia3 * 2u];
306 <a name="l00294"></a>00294 si3 = pCoef[(ia3 * 2u) + 1u];
307 <a name="l00295"></a>00295 <span class="comment">/* Twiddle coefficients index modifier */</span>
308 <a name="l00296"></a>00296 ia1 = ia1 + twidCoefModifier;
309 <a name="l00297"></a>00297
310 <a name="l00298"></a>00298 <span class="keywordflow">for</span> (i0 = j; i0 < fftLen; i0 += n1)
311 <a name="l00299"></a>00299 {
312 <a name="l00300"></a>00300 <span class="comment">/* index calculation for the input as, */</span>
313 <a name="l00301"></a>00301 <span class="comment">/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2u], pSrc[i0 + 3fftLen/4] */</span>
314 <a name="l00302"></a>00302 i1 = i0 + n2;
315 <a name="l00303"></a>00303 i2 = i1 + n2;
316 <a name="l00304"></a>00304 i3 = i2 + n2;
317 <a name="l00305"></a>00305
318 <a name="l00306"></a>00306 <span class="comment">/* Butterfly implementation */</span>
319 <a name="l00307"></a>00307 <span class="comment">/* xa + xc */</span>
320 <a name="l00308"></a>00308 r1 = pSrc[2u * i0] + pSrc[2u * i2];
321 <a name="l00309"></a>00309 <span class="comment">/* xa - xc */</span>
322 <a name="l00310"></a>00310 r2 = pSrc[2u * i0] - pSrc[2u * i2];
323 <a name="l00311"></a>00311
324 <a name="l00312"></a>00312 <span class="comment">/* ya + yc */</span>
325 <a name="l00313"></a>00313 s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];
326 <a name="l00314"></a>00314 <span class="comment">/* ya - yc */</span>
327 <a name="l00315"></a>00315 s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];
328 <a name="l00316"></a>00316
329 <a name="l00317"></a>00317 <span class="comment">/* xb + xd */</span>
330 <a name="l00318"></a>00318 t1 = pSrc[2u * i1] + pSrc[2u * i3];
331 <a name="l00319"></a>00319
332 <a name="l00320"></a>00320 <span class="comment">/* xa' = xa + xb + xc + xd */</span>
333 <a name="l00321"></a>00321 pSrc[2u * i0] = (r1 + t1) >> 2u;
334 <a name="l00322"></a>00322 <span class="comment">/* xa + xc -(xb + xd) */</span>
335 <a name="l00323"></a>00323 r1 = r1 - t1;
336 <a name="l00324"></a>00324
337 <a name="l00325"></a>00325 <span class="comment">/* yb + yd */</span>
338 <a name="l00326"></a>00326 t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];
339 <a name="l00327"></a>00327 <span class="comment">/* ya' = ya + yb + yc + yd */</span>
340 <a name="l00328"></a>00328 pSrc[(2u * i0) + 1u] = (s1 + t2) >> 2u;
341 <a name="l00329"></a>00329
342 <a name="l00330"></a>00330 <span class="comment">/* (ya + yc) - (yb + yd) */</span>
343 <a name="l00331"></a>00331 s1 = s1 - t2;
344 <a name="l00332"></a>00332
345 <a name="l00333"></a>00333 <span class="comment">/* (yb - yd) */</span>
346 <a name="l00334"></a>00334 t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];
347 <a name="l00335"></a>00335 <span class="comment">/* (xb - xd) */</span>
348 <a name="l00336"></a>00336 t2 = pSrc[2u * i1] - pSrc[2u * i3];
349 <a name="l00337"></a>00337
350 <a name="l00338"></a>00338 <span class="comment">/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */</span>
351 <a name="l00339"></a>00339 pSrc[2u * i1] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co2) >> 32)) +
352 <a name="l00340"></a>00340 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si2) >> 32))) >> 1u;
353 <a name="l00341"></a>00341
354 <a name="l00342"></a>00342 <span class="comment">/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */</span>
355 <a name="l00343"></a>00343 pSrc[(2u * i1) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co2) >> 32)) -
356 <a name="l00344"></a>00344 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si2) >> 32))) >> 1u;
357 <a name="l00345"></a>00345
358 <a name="l00346"></a>00346 <span class="comment">/* (xa - xc) + (yb - yd) */</span>
359 <a name="l00347"></a>00347 r1 = r2 + t1;
360 <a name="l00348"></a>00348 <span class="comment">/* (xa - xc) - (yb - yd) */</span>
361 <a name="l00349"></a>00349 r2 = r2 - t1;
362 <a name="l00350"></a>00350
363 <a name="l00351"></a>00351 <span class="comment">/* (ya - yc) - (xb - xd) */</span>
364 <a name="l00352"></a>00352 s1 = s2 - t2;
365 <a name="l00353"></a>00353 <span class="comment">/* (ya - yc) + (xb - xd) */</span>
366 <a name="l00354"></a>00354 s2 = s2 + t2;
367 <a name="l00355"></a>00355
368 <a name="l00356"></a>00356 <span class="comment">/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */</span>
369 <a name="l00357"></a>00357 pSrc[2u * i2] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co1) >> 32)) +
370 <a name="l00358"></a>00358 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si1) >> 32))) >> 1u;
371 <a name="l00359"></a>00359
372 <a name="l00360"></a>00360 <span class="comment">/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */</span>
373 <a name="l00361"></a>00361 pSrc[(2u * i2) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co1) >> 32)) -
374 <a name="l00362"></a>00362 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si1) >> 32))) >> 1u;
375 <a name="l00363"></a>00363
376 <a name="l00364"></a>00364 <span class="comment">/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */</span>
377 <a name="l00365"></a>00365 pSrc[2u * i3] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * co3) >> 32)) +
378 <a name="l00366"></a>00366 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * si3) >> 32))) >> 1u;
379 <a name="l00367"></a>00367
380 <a name="l00368"></a>00368 <span class="comment">/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */</span>
381 <a name="l00369"></a>00369 pSrc[(2u * i3) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * co3) >> 32)) -
382 <a name="l00370"></a>00370 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * si3) >> 32))) >> 1u;
383 <a name="l00371"></a>00371 }
384 <a name="l00372"></a>00372 }
385 <a name="l00373"></a>00373 twidCoefModifier <<= 2u;
386 <a name="l00374"></a>00374 }
387 <a name="l00375"></a>00375
388 <a name="l00376"></a>00376 <span class="comment">/* End of Middle stages process */</span>
389 <a name="l00377"></a>00377
390 <a name="l00378"></a>00378 <span class="comment">/* data is in 11.21(q21) format for the 1024 point as there are 3 middle stages */</span>
391 <a name="l00379"></a>00379 <span class="comment">/* data is in 9.23(q23) format for the 256 point as there are 2 middle stages */</span>
392 <a name="l00380"></a>00380 <span class="comment">/* data is in 7.25(q25) format for the 64 point as there are 1 middle stage */</span>
393 <a name="l00381"></a>00381 <span class="comment">/* data is in 5.27(q27) format for the 16 point as there are no middle stages */</span>
394 <a name="l00382"></a>00382
395 <a name="l00383"></a>00383
396 <a name="l00384"></a>00384 <span class="comment">/* start of Last stage process */</span>
397 <a name="l00385"></a>00385
398 <a name="l00386"></a>00386 <span class="comment">/* Initializations of last stage */</span>
399 <a name="l00387"></a>00387 n1 = n2;
400 <a name="l00388"></a>00388 n2 >>= 2u;
401 <a name="l00389"></a>00389
402 <a name="l00390"></a>00390 <span class="comment">/* Calculations of last stage */</span>
403 <a name="l00391"></a>00391 <span class="keywordflow">for</span> (i0 = 0u; i0 <= (fftLen - n1); i0 += n1)
404 <a name="l00392"></a>00392 {
405 <a name="l00393"></a>00393 <span class="comment">/* index calculation for the input as, */</span>
406 <a name="l00394"></a>00394 <span class="comment">/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2u], pSrc[i0 + 3fftLen/4] */</span>
407 <a name="l00395"></a>00395 i1 = i0 + n2;
408 <a name="l00396"></a>00396 i2 = i1 + n2;
409 <a name="l00397"></a>00397 i3 = i2 + n2;
410 <a name="l00398"></a>00398
411 <a name="l00399"></a>00399 <span class="comment">/* Butterfly implementation */</span>
412 <a name="l00400"></a>00400 <span class="comment">/* xa + xb */</span>
413 <a name="l00401"></a>00401 r1 = pSrc[2u * i0] + pSrc[2u * i2];
414 <a name="l00402"></a>00402 <span class="comment">/* xa - xb */</span>
415 <a name="l00403"></a>00403 r2 = pSrc[2u * i0] - pSrc[2u * i2];
416 <a name="l00404"></a>00404
417 <a name="l00405"></a>00405 <span class="comment">/* ya + yc */</span>
418 <a name="l00406"></a>00406 s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];
419 <a name="l00407"></a>00407 <span class="comment">/* ya - yc */</span>
420 <a name="l00408"></a>00408 s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];
421 <a name="l00409"></a>00409
422 <a name="l00410"></a>00410 <span class="comment">/* xc + xd */</span>
423 <a name="l00411"></a>00411 t1 = pSrc[2u * i1] + pSrc[2u * i3];
424 <a name="l00412"></a>00412 <span class="comment">/* xa' = xa + xb + xc + xd */</span>
425 <a name="l00413"></a>00413 pSrc[2u * i0] = (r1 + t1);
426 <a name="l00414"></a>00414 <span class="comment">/* (xa + xb) - (xc + xd) */</span>
427 <a name="l00415"></a>00415 r1 = r1 - t1;
428 <a name="l00416"></a>00416
429 <a name="l00417"></a>00417 <span class="comment">/* yb + yd */</span>
430 <a name="l00418"></a>00418 t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];
431 <a name="l00419"></a>00419 <span class="comment">/* ya' = ya + yb + yc + yd */</span>
432 <a name="l00420"></a>00420 pSrc[(2u * i0) + 1u] = (s1 + t2);
433 <a name="l00421"></a>00421 <span class="comment">/* (ya + yc) - (yb + yd) */</span>
434 <a name="l00422"></a>00422 s1 = s1 - t2;
435 <a name="l00423"></a>00423
436 <a name="l00424"></a>00424 <span class="comment">/* (yb-yd) */</span>
437 <a name="l00425"></a>00425 t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];
438 <a name="l00426"></a>00426 <span class="comment">/* (xb-xd) */</span>
439 <a name="l00427"></a>00427 t2 = pSrc[2u * i1] - pSrc[2u * i3];
440 <a name="l00428"></a>00428
441 <a name="l00429"></a>00429 <span class="comment">/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */</span>
442 <a name="l00430"></a>00430 pSrc[2u * i1] = r1;
443 <a name="l00431"></a>00431 <span class="comment">/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */</span>
444 <a name="l00432"></a>00432 pSrc[(2u * i1) + 1u] = s1;
445 <a name="l00433"></a>00433
446 <a name="l00434"></a>00434 <span class="comment">/* (xa+yb-xc-yd) */</span>
447 <a name="l00435"></a>00435 r1 = r2 + t1;
448 <a name="l00436"></a>00436 <span class="comment">/* (xa-yb-xc+yd) */</span>
449 <a name="l00437"></a>00437 r2 = r2 - t1;
450 <a name="l00438"></a>00438
451 <a name="l00439"></a>00439 <span class="comment">/* (ya-xb-yc+xd) */</span>
452 <a name="l00440"></a>00440 s1 = s2 - t2;
453 <a name="l00441"></a>00441 <span class="comment">/* (ya+xb-yc-xd) */</span>
454 <a name="l00442"></a>00442 s2 = s2 + t2;
455 <a name="l00443"></a>00443
456 <a name="l00444"></a>00444 <span class="comment">/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */</span>
457 <a name="l00445"></a>00445 pSrc[2u * i2] = r1;
458 <a name="l00446"></a>00446 <span class="comment">/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */</span>
459 <a name="l00447"></a>00447 pSrc[(2u * i2) + 1u] = s1;
460 <a name="l00448"></a>00448
461 <a name="l00449"></a>00449 <span class="comment">/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */</span>
462 <a name="l00450"></a>00450 pSrc[2u * i3] = r2;
463 <a name="l00451"></a>00451 <span class="comment">/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */</span>
464 <a name="l00452"></a>00452 pSrc[(2u * i3) + 1u] = s2;
465 <a name="l00453"></a>00453
466 <a name="l00454"></a>00454
467 <a name="l00455"></a>00455 }
468 <a name="l00456"></a>00456
469 <a name="l00457"></a>00457 <span class="comment">/* output is in 11.21(q21) format for the 1024 point */</span>
470 <a name="l00458"></a>00458 <span class="comment">/* output is in 9.23(q23) format for the 256 point */</span>
471 <a name="l00459"></a>00459 <span class="comment">/* output is in 7.25(q25) format for the 64 point */</span>
472 <a name="l00460"></a>00460 <span class="comment">/* output is in 5.27(q27) format for the 16 point */</span>
473 <a name="l00461"></a>00461
474 <a name="l00462"></a>00462 <span class="comment">/* End of last stage process */</span>
475 <a name="l00463"></a>00463
476 <a name="l00464"></a>00464 }
477 <a name="l00465"></a>00465
478 <a name="l00466"></a>00466
479 <a name="l00477"></a>00477 <span class="comment">/* </span>
480 <a name="l00478"></a>00478 <span class="comment">* Radix-4 IFFT algorithm used is : </span>
481 <a name="l00479"></a>00479 <span class="comment">* </span>
482 <a name="l00480"></a>00480 <span class="comment">* CIFFT uses same twiddle coefficients as CFFT Function </span>
483 <a name="l00481"></a>00481 <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>
484 <a name="l00482"></a>00482 <span class="comment">* </span>
485 <a name="l00483"></a>00483 <span class="comment">* </span>
486 <a name="l00484"></a>00484 <span class="comment">* IFFT is implemented with following changes in equations from FFT </span>
487 <a name="l00485"></a>00485 <span class="comment">* </span>
488 <a name="l00486"></a>00486 <span class="comment">* Input real and imaginary data: </span>
489 <a name="l00487"></a>00487 <span class="comment">* x(n) = xa + j * ya </span>
490 <a name="l00488"></a>00488 <span class="comment">* x(n+N/4 ) = xb + j * yb </span>
491 <a name="l00489"></a>00489 <span class="comment">* x(n+N/2 ) = xc + j * yc </span>
492 <a name="l00490"></a>00490 <span class="comment">* x(n+3N 4) = xd + j * yd </span>
493 <a name="l00491"></a>00491 <span class="comment">* </span>
494 <a name="l00492"></a>00492 <span class="comment">* </span>
495 <a name="l00493"></a>00493 <span class="comment">* Output real and imaginary data: </span>
496 <a name="l00494"></a>00494 <span class="comment">* x(4r) = xa'+ j * ya' </span>
497 <a name="l00495"></a>00495 <span class="comment">* x(4r+1) = xb'+ j * yb' </span>
498 <a name="l00496"></a>00496 <span class="comment">* x(4r+2) = xc'+ j * yc' </span>
499 <a name="l00497"></a>00497 <span class="comment">* x(4r+3) = xd'+ j * yd' </span>
500 <a name="l00498"></a>00498 <span class="comment">* </span>
501 <a name="l00499"></a>00499 <span class="comment">* </span>
502 <a name="l00500"></a>00500 <span class="comment">* Twiddle factors for radix-4 IFFT: </span>
503 <a name="l00501"></a>00501 <span class="comment">* Wn = co1 + j * (si1) </span>
504 <a name="l00502"></a>00502 <span class="comment">* W2n = co2 + j * (si2) </span>
505 <a name="l00503"></a>00503 <span class="comment">* W3n = co3 + j * (si3) </span>
506 <a name="l00504"></a>00504 <span class="comment"> </span>
507 <a name="l00505"></a>00505 <span class="comment">* The real and imaginary output values for the radix-4 butterfly are </span>
508 <a name="l00506"></a>00506 <span class="comment">* xa' = xa + xb + xc + xd </span>
509 <a name="l00507"></a>00507 <span class="comment">* ya' = ya + yb + yc + yd </span>
510 <a name="l00508"></a>00508 <span class="comment">* xb' = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) </span>
511 <a name="l00509"></a>00509 <span class="comment">* yb' = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) </span>
512 <a name="l00510"></a>00510 <span class="comment">* xc' = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) </span>
513 <a name="l00511"></a>00511 <span class="comment">* yc' = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) </span>
514 <a name="l00512"></a>00512 <span class="comment">* xd' = (xa+yb-xc-yd)* co3 - (ya-xb-yc+xd)* (si3) </span>
515 <a name="l00513"></a>00513 <span class="comment">* yd' = (ya-xb-yc+xd)* co3 + (xa+yb-xc-yd)* (si3) </span>
516 <a name="l00514"></a>00514 <span class="comment">* </span>
517 <a name="l00515"></a>00515 <span class="comment">*/</span>
518 <a name="l00516"></a>00516
519 <a name="l00517"></a><a class="code" href="arm__math_8h.html#ac9c7c553114c1201a3a987a11b8a6d01">00517</a> <span class="keywordtype">void</span> <a class="code" href="arm__cfft__radix4__q31_8c.html#ac9c7c553114c1201a3a987a11b8a6d01" title="Core function for the Q31 CIFFT butterfly process.">arm_radix4_butterfly_inverse_q31</a>(
520 <a name="l00518"></a>00518 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> * pSrc,
521 <a name="l00519"></a>00519 uint32_t fftLen,
522 <a name="l00520"></a>00520 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> * pCoef,
523 <a name="l00521"></a>00521 uint32_t twidCoefModifier)
524 <a name="l00522"></a>00522 {
525 <a name="l00523"></a>00523 uint32_t n1, n2, ia1, ia2, ia3, i0, i1, i2, i3, j, k;
526 <a name="l00524"></a>00524 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> t1, t2, r1, r2, s1, s2, co1, co2, co3, si1, si2, si3;
527 <a name="l00525"></a>00525
528 <a name="l00526"></a>00526 <span class="comment">/* input is be 1.31(q31) format for all FFT sizes */</span>
529 <a name="l00527"></a>00527 <span class="comment">/* Total process is divided into three stages */</span>
530 <a name="l00528"></a>00528 <span class="comment">/* process first stage, middle stages, & last stage */</span>
531 <a name="l00529"></a>00529
532 <a name="l00530"></a>00530 <span class="comment">/* Start of first stage process */</span>
533 <a name="l00531"></a>00531
534 <a name="l00532"></a>00532 <span class="comment">/* Initializations for the first stage */</span>
535 <a name="l00533"></a>00533 n2 = fftLen;
536 <a name="l00534"></a>00534 n1 = n2;
537 <a name="l00535"></a>00535 <span class="comment">/* n2 = fftLen/4 */</span>
538 <a name="l00536"></a>00536 n2 >>= 2u;
539 <a name="l00537"></a>00537 i0 = 0u;
540 <a name="l00538"></a>00538 ia1 = 0u;
541 <a name="l00539"></a>00539
542 <a name="l00540"></a>00540 j = n2;
543 <a name="l00541"></a>00541
544 <a name="l00542"></a>00542 <span class="keywordflow">do</span>
545 <a name="l00543"></a>00543 {
546 <a name="l00544"></a>00544
547 <a name="l00545"></a>00545 <span class="comment">/* input is in 1.31(q31) format and provide 4 guard bits for the input */</span>
548 <a name="l00546"></a>00546
549 <a name="l00547"></a>00547 <span class="comment">/* index calculation for the input as, */</span>
550 <a name="l00548"></a>00548 <span class="comment">/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2u], pSrc[i0 + 3fftLen/4] */</span>
551 <a name="l00549"></a>00549 i1 = i0 + n2;
552 <a name="l00550"></a>00550 i2 = i1 + n2;
553 <a name="l00551"></a>00551 i3 = i2 + n2;
554 <a name="l00552"></a>00552
555 <a name="l00553"></a>00553 <span class="comment">/* Butterfly implementation */</span>
556 <a name="l00554"></a>00554 <span class="comment">/* xa + xc */</span>
557 <a name="l00555"></a>00555 r1 = (pSrc[2u * i0] >> 4u) + (pSrc[2u * i2] >> 4u);
558 <a name="l00556"></a>00556 <span class="comment">/* xa - xc */</span>
559 <a name="l00557"></a>00557 r2 = (pSrc[2u * i0] >> 4u) - (pSrc[2u * i2] >> 4u);
560 <a name="l00558"></a>00558
561 <a name="l00559"></a>00559 <span class="comment">/* ya + yc */</span>
562 <a name="l00560"></a>00560 s1 = (pSrc[(2u * i0) + 1u] >> 4u) + (pSrc[(2u * i2) + 1u] >> 4u);
563 <a name="l00561"></a>00561 <span class="comment">/* ya - yc */</span>
564 <a name="l00562"></a>00562 s2 = (pSrc[(2u * i0) + 1u] >> 4u) - (pSrc[(2u * i2) + 1u] >> 4u);
565 <a name="l00563"></a>00563
566 <a name="l00564"></a>00564 <span class="comment">/* xb + xd */</span>
567 <a name="l00565"></a>00565 t1 = (pSrc[2u * i1] >> 4u) + (pSrc[2u * i3] >> 4u);
568 <a name="l00566"></a>00566
569 <a name="l00567"></a>00567 <span class="comment">/* xa' = xa + xb + xc + xd */</span>
570 <a name="l00568"></a>00568 pSrc[2u * i0] = (r1 + t1);
571 <a name="l00569"></a>00569 <span class="comment">/* (xa + xc) - (xb + xd) */</span>
572 <a name="l00570"></a>00570 r1 = r1 - t1;
573 <a name="l00571"></a>00571 <span class="comment">/* yb + yd */</span>
574 <a name="l00572"></a>00572 t2 = (pSrc[(2u * i1) + 1u] >> 4u) + (pSrc[(2u * i3) + 1u] >> 4u);
575 <a name="l00573"></a>00573 <span class="comment">/* ya' = ya + yb + yc + yd */</span>
576 <a name="l00574"></a>00574 pSrc[(2u * i0) + 1u] = (s1 + t2);
577 <a name="l00575"></a>00575
578 <a name="l00576"></a>00576 <span class="comment">/* (ya + yc) - (yb + yd) */</span>
579 <a name="l00577"></a>00577 s1 = s1 - t2;
580 <a name="l00578"></a>00578
581 <a name="l00579"></a>00579 <span class="comment">/* yb - yd */</span>
582 <a name="l00580"></a>00580 t1 = (pSrc[(2u * i1) + 1u] >> 4u) - (pSrc[(2u * i3) + 1u] >> 4u);
583 <a name="l00581"></a>00581 <span class="comment">/* xb - xd */</span>
584 <a name="l00582"></a>00582 t2 = (pSrc[2u * i1] >> 4u) - (pSrc[2u * i3] >> 4u);
585 <a name="l00583"></a>00583
586 <a name="l00584"></a>00584 <span class="comment">/* index calculation for the coefficients */</span>
587 <a name="l00585"></a>00585 ia2 = 2u * ia1;
588 <a name="l00586"></a>00586 co2 = pCoef[ia2 * 2u];
589 <a name="l00587"></a>00587 si2 = pCoef[(ia2 * 2u) + 1u];
590 <a name="l00588"></a>00588
591 <a name="l00589"></a>00589 <span class="comment">/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */</span>
592 <a name="l00590"></a>00590 pSrc[2u * i1] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co2) >> 32)) -
593 <a name="l00591"></a>00591 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si2) >> 32))) << 1u;
594 <a name="l00592"></a>00592
595 <a name="l00593"></a>00593 <span class="comment">/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */</span>
596 <a name="l00594"></a>00594 pSrc[2u * i1 + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co2) >> 32)) +
597 <a name="l00595"></a>00595 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si2) >> 32))) << 1u;
598 <a name="l00596"></a>00596
599 <a name="l00597"></a>00597 <span class="comment">/* (xa - xc) - (yb - yd) */</span>
600 <a name="l00598"></a>00598 r1 = r2 - t1;
601 <a name="l00599"></a>00599 <span class="comment">/* (xa - xc) + (yb - yd) */</span>
602 <a name="l00600"></a>00600 r2 = r2 + t1;
603 <a name="l00601"></a>00601
604 <a name="l00602"></a>00602 <span class="comment">/* (ya - yc) + (xb - xd) */</span>
605 <a name="l00603"></a>00603 s1 = s2 + t2;
606 <a name="l00604"></a>00604 <span class="comment">/* (ya - yc) - (xb - xd) */</span>
607 <a name="l00605"></a>00605 s2 = s2 - t2;
608 <a name="l00606"></a>00606
609 <a name="l00607"></a>00607 co1 = pCoef[ia1 * 2u];
610 <a name="l00608"></a>00608 si1 = pCoef[(ia1 * 2u) + 1u];
611 <a name="l00609"></a>00609
612 <a name="l00610"></a>00610 <span class="comment">/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */</span>
613 <a name="l00611"></a>00611 pSrc[2u * i2] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co1) >> 32)) -
614 <a name="l00612"></a>00612 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si1) >> 32))) << 1u;
615 <a name="l00613"></a>00613
616 <a name="l00614"></a>00614 <span class="comment">/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */</span>
617 <a name="l00615"></a>00615 pSrc[(2u * i2) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co1) >> 32)) +
618 <a name="l00616"></a>00616 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si1) >> 32))) << 1u;
619 <a name="l00617"></a>00617
620 <a name="l00618"></a>00618 <span class="comment">/* index calculation for the coefficients */</span>
621 <a name="l00619"></a>00619 ia3 = 3u * ia1;
622 <a name="l00620"></a>00620 co3 = pCoef[ia3 * 2u];
623 <a name="l00621"></a>00621 si3 = pCoef[(ia3 * 2u) + 1u];
624 <a name="l00622"></a>00622
625 <a name="l00623"></a>00623 <span class="comment">/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */</span>
626 <a name="l00624"></a>00624 pSrc[2u * i3] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * co3) >> 32)) -
627 <a name="l00625"></a>00625 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * si3) >> 32))) << 1u;
628 <a name="l00626"></a>00626
629 <a name="l00627"></a>00627 <span class="comment">/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */</span>
630 <a name="l00628"></a>00628 pSrc[(2u * i3) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * co3) >> 32)) +
631 <a name="l00629"></a>00629 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * si3) >> 32))) << 1u;
632 <a name="l00630"></a>00630
633 <a name="l00631"></a>00631 <span class="comment">/* Twiddle coefficients index modifier */</span>
634 <a name="l00632"></a>00632 ia1 = ia1 + twidCoefModifier;
635 <a name="l00633"></a>00633
636 <a name="l00634"></a>00634 <span class="comment">/* Updating input index */</span>
637 <a name="l00635"></a>00635 i0 = i0 + 1u;
638 <a name="l00636"></a>00636
639 <a name="l00637"></a>00637 } <span class="keywordflow">while</span>(--j);
640 <a name="l00638"></a>00638
641 <a name="l00639"></a>00639 <span class="comment">/* data is in 5.27(q27) format */</span>
642 <a name="l00640"></a>00640 <span class="comment">/* each stage provides two down scaling of the input */</span>
643 <a name="l00641"></a>00641
644 <a name="l00642"></a>00642
645 <a name="l00643"></a>00643 <span class="comment">/* Start of Middle stages process */</span>
646 <a name="l00644"></a>00644
647 <a name="l00645"></a>00645 twidCoefModifier <<= 2u;
648 <a name="l00646"></a>00646
649 <a name="l00647"></a>00647 <span class="comment">/* Calculation of second stage to excluding last stage */</span>
650 <a name="l00648"></a>00648 <span class="keywordflow">for</span> (k = fftLen / 4u; k > 4u; k >>= 2u)
651 <a name="l00649"></a>00649 {
652 <a name="l00650"></a>00650 <span class="comment">/* Initializations for the first stage */</span>
653 <a name="l00651"></a>00651 n1 = n2;
654 <a name="l00652"></a>00652 n2 >>= 2u;
655 <a name="l00653"></a>00653 ia1 = 0u;
656 <a name="l00654"></a>00654
657 <a name="l00655"></a>00655 <span class="keywordflow">for</span> (j = 0; j <= (n2 - 1u); j++)
658 <a name="l00656"></a>00656 {
659 <a name="l00657"></a>00657 <span class="comment">/* index calculation for the coefficients */</span>
660 <a name="l00658"></a>00658 ia2 = ia1 + ia1;
661 <a name="l00659"></a>00659 ia3 = ia2 + ia1;
662 <a name="l00660"></a>00660 co1 = pCoef[ia1 * 2u];
663 <a name="l00661"></a>00661 si1 = pCoef[(ia1 * 2u) + 1u];
664 <a name="l00662"></a>00662 co2 = pCoef[ia2 * 2u];
665 <a name="l00663"></a>00663 si2 = pCoef[(ia2 * 2u) + 1u];
666 <a name="l00664"></a>00664 co3 = pCoef[ia3 * 2u];
667 <a name="l00665"></a>00665 si3 = pCoef[(ia3 * 2u) + 1u];
668 <a name="l00666"></a>00666 <span class="comment">/* Twiddle coefficients index modifier */</span>
669 <a name="l00667"></a>00667 ia1 = ia1 + twidCoefModifier;
670 <a name="l00668"></a>00668
671 <a name="l00669"></a>00669 <span class="keywordflow">for</span> (i0 = j; i0 < fftLen; i0 += n1)
672 <a name="l00670"></a>00670 {
673 <a name="l00671"></a>00671 <span class="comment">/* index calculation for the input as, */</span>
674 <a name="l00672"></a>00672 <span class="comment">/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2u], pSrc[i0 + 3fftLen/4] */</span>
675 <a name="l00673"></a>00673 i1 = i0 + n2;
676 <a name="l00674"></a>00674 i2 = i1 + n2;
677 <a name="l00675"></a>00675 i3 = i2 + n2;
678 <a name="l00676"></a>00676
679 <a name="l00677"></a>00677 <span class="comment">/* Butterfly implementation */</span>
680 <a name="l00678"></a>00678 <span class="comment">/* xa + xc */</span>
681 <a name="l00679"></a>00679 r1 = pSrc[2u * i0] + pSrc[2u * i2];
682 <a name="l00680"></a>00680 <span class="comment">/* xa - xc */</span>
683 <a name="l00681"></a>00681 r2 = pSrc[2u * i0] - pSrc[2u * i2];
684 <a name="l00682"></a>00682
685 <a name="l00683"></a>00683 <span class="comment">/* ya + yc */</span>
686 <a name="l00684"></a>00684 s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];
687 <a name="l00685"></a>00685 <span class="comment">/* ya - yc */</span>
688 <a name="l00686"></a>00686 s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];
689 <a name="l00687"></a>00687
690 <a name="l00688"></a>00688 <span class="comment">/* xb + xd */</span>
691 <a name="l00689"></a>00689 t1 = pSrc[2u * i1] + pSrc[2u * i3];
692 <a name="l00690"></a>00690
693 <a name="l00691"></a>00691 <span class="comment">/* xa' = xa + xb + xc + xd */</span>
694 <a name="l00692"></a>00692 pSrc[2u * i0] = (r1 + t1) >> 2u;
695 <a name="l00693"></a>00693 <span class="comment">/* xa + xc -(xb + xd) */</span>
696 <a name="l00694"></a>00694 r1 = r1 - t1;
697 <a name="l00695"></a>00695 <span class="comment">/* yb + yd */</span>
698 <a name="l00696"></a>00696 t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];
699 <a name="l00697"></a>00697 <span class="comment">/* ya' = ya + yb + yc + yd */</span>
700 <a name="l00698"></a>00698 pSrc[(2u * i0) + 1u] = (s1 + t2) >> 2u;
701 <a name="l00699"></a>00699
702 <a name="l00700"></a>00700 <span class="comment">/* (ya + yc) - (yb + yd) */</span>
703 <a name="l00701"></a>00701 s1 = s1 - t2;
704 <a name="l00702"></a>00702
705 <a name="l00703"></a>00703 <span class="comment">/* (yb - yd) */</span>
706 <a name="l00704"></a>00704 t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];
707 <a name="l00705"></a>00705 <span class="comment">/* (xb - xd) */</span>
708 <a name="l00706"></a>00706 t2 = pSrc[2u * i1] - pSrc[2u * i3];
709 <a name="l00707"></a>00707
710 <a name="l00708"></a>00708 <span class="comment">/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */</span>
711 <a name="l00709"></a>00709 pSrc[2u * i1] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co2) >> 32u)) -
712 <a name="l00710"></a>00710 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si2) >> 32u))) >> 1u;
713 <a name="l00711"></a>00711
714 <a name="l00712"></a>00712 <span class="comment">/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */</span>
715 <a name="l00713"></a>00713 pSrc[(2u * i1) + 1u] =
716 <a name="l00714"></a>00714 (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co2) >> 32u)) +
717 <a name="l00715"></a>00715 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si2) >> 32u))) >> 1u;
718 <a name="l00716"></a>00716
719 <a name="l00717"></a>00717 <span class="comment">/* (xa - xc) - (yb - yd) */</span>
720 <a name="l00718"></a>00718 r1 = r2 - t1;
721 <a name="l00719"></a>00719 <span class="comment">/* (xa - xc) + (yb - yd) */</span>
722 <a name="l00720"></a>00720 r2 = r2 + t1;
723 <a name="l00721"></a>00721
724 <a name="l00722"></a>00722 <span class="comment">/* (ya - yc) + (xb - xd) */</span>
725 <a name="l00723"></a>00723 s1 = s2 + t2;
726 <a name="l00724"></a>00724 <span class="comment">/* (ya - yc) - (xb - xd) */</span>
727 <a name="l00725"></a>00725 s2 = s2 - t2;
728 <a name="l00726"></a>00726
729 <a name="l00727"></a>00727 <span class="comment">/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */</span>
730 <a name="l00728"></a>00728 pSrc[2u * i2] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * co1) >> 32)) -
731 <a name="l00729"></a>00729 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * si1) >> 32))) >> 1u;
732 <a name="l00730"></a>00730
733 <a name="l00731"></a>00731 <span class="comment">/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */</span>
734 <a name="l00732"></a>00732 pSrc[(2u * i2) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s1 * co1) >> 32)) +
735 <a name="l00733"></a>00733 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r1 * si1) >> 32))) >> 1u;
736 <a name="l00734"></a>00734
737 <a name="l00735"></a>00735 <span class="comment">/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */</span>
738 <a name="l00736"></a>00736 pSrc[(2u * i3)] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * co3) >> 32)) -
739 <a name="l00737"></a>00737 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * si3) >> 32))) >> 1u;
740 <a name="l00738"></a>00738
741 <a name="l00739"></a>00739 <span class="comment">/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */</span>
742 <a name="l00740"></a>00740 pSrc[(2u * i3) + 1u] = (((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) s2 * co3) >> 32)) +
743 <a name="l00741"></a>00741 ((int32_t) (((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) r2 * si3) >> 32))) >> 1u;
744 <a name="l00742"></a>00742 }
745 <a name="l00743"></a>00743 }
746 <a name="l00744"></a>00744 twidCoefModifier <<= 2u;
747 <a name="l00745"></a>00745 }
748 <a name="l00746"></a>00746
749 <a name="l00747"></a>00747 <span class="comment">/* End of Middle stages process */</span>
750 <a name="l00748"></a>00748
751 <a name="l00749"></a>00749 <span class="comment">/* data is in 11.21(q21) format for the 1024 point as there are 3 middle stages */</span>
752 <a name="l00750"></a>00750 <span class="comment">/* data is in 9.23(q23) format for the 256 point as there are 2 middle stages */</span>
753 <a name="l00751"></a>00751 <span class="comment">/* data is in 7.25(q25) format for the 64 point as there are 1 middle stage */</span>
754 <a name="l00752"></a>00752 <span class="comment">/* data is in 5.27(q27) format for the 16 point as there are no middle stages */</span>
755 <a name="l00753"></a>00753
756 <a name="l00754"></a>00754
757 <a name="l00755"></a>00755 <span class="comment">/* Start of last stage process */</span>
758 <a name="l00756"></a>00756
759 <a name="l00757"></a>00757
760 <a name="l00758"></a>00758 <span class="comment">/* Initializations of last stage */</span>
761 <a name="l00759"></a>00759 n1 = n2;
762 <a name="l00760"></a>00760 n2 >>= 2u;
763 <a name="l00761"></a>00761
764 <a name="l00762"></a>00762 <span class="comment">/* Calculations of last stage */</span>
765 <a name="l00763"></a>00763 <span class="keywordflow">for</span> (i0 = 0u; i0 <= (fftLen - n1); i0 += n1)
766 <a name="l00764"></a>00764 {
767 <a name="l00765"></a>00765 <span class="comment">/* index calculation for the input as, */</span>
768 <a name="l00766"></a>00766 <span class="comment">/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2u], pSrc[i0 + 3fftLen/4] */</span>
769 <a name="l00767"></a>00767 i1 = i0 + n2;
770 <a name="l00768"></a>00768 i2 = i1 + n2;
771 <a name="l00769"></a>00769 i3 = i2 + n2;
772 <a name="l00770"></a>00770
773 <a name="l00771"></a>00771 <span class="comment">/* Butterfly implementation */</span>
774 <a name="l00772"></a>00772 <span class="comment">/* xa + xc */</span>
775 <a name="l00773"></a>00773 r1 = pSrc[2u * i0] + pSrc[2u * i2];
776 <a name="l00774"></a>00774 <span class="comment">/* xa - xc */</span>
777 <a name="l00775"></a>00775 r2 = pSrc[2u * i0] - pSrc[2u * i2];
778 <a name="l00776"></a>00776
779 <a name="l00777"></a>00777 <span class="comment">/* ya + yc */</span>
780 <a name="l00778"></a>00778 s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];
781 <a name="l00779"></a>00779 <span class="comment">/* ya - yc */</span>
782 <a name="l00780"></a>00780 s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];
783 <a name="l00781"></a>00781
784 <a name="l00782"></a>00782 <span class="comment">/* xc + xd */</span>
785 <a name="l00783"></a>00783 t1 = pSrc[2u * i1] + pSrc[2u * i3];
786 <a name="l00784"></a>00784 <span class="comment">/* xa' = xa + xb + xc + xd */</span>
787 <a name="l00785"></a>00785 pSrc[2u * i0] = (r1 + t1);
788 <a name="l00786"></a>00786 <span class="comment">/* (xa + xb) - (xc + xd) */</span>
789 <a name="l00787"></a>00787 r1 = r1 - t1;
790 <a name="l00788"></a>00788
791 <a name="l00789"></a>00789 <span class="comment">/* yb + yd */</span>
792 <a name="l00790"></a>00790 t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];
793 <a name="l00791"></a>00791 <span class="comment">/* ya' = ya + yb + yc + yd */</span>
794 <a name="l00792"></a>00792 pSrc[(2u * i0) + 1u] = (s1 + t2);
795 <a name="l00793"></a>00793 <span class="comment">/* (ya + yc) - (yb + yd) */</span>
796 <a name="l00794"></a>00794 s1 = s1 - t2;
797 <a name="l00795"></a>00795
798 <a name="l00796"></a>00796 <span class="comment">/* (yb-yd) */</span>
799 <a name="l00797"></a>00797 t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];
800 <a name="l00798"></a>00798 <span class="comment">/* (xb-xd) */</span>
801 <a name="l00799"></a>00799 t2 = pSrc[2u * i1] - pSrc[2u * i3];
802 <a name="l00800"></a>00800
803 <a name="l00801"></a>00801 <span class="comment">/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */</span>
804 <a name="l00802"></a>00802 pSrc[2u * i1] = r1;
805 <a name="l00803"></a>00803 <span class="comment">/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */</span>
806 <a name="l00804"></a>00804 pSrc[(2u * i1) + 1u] = s1;
807 <a name="l00805"></a>00805
808 <a name="l00806"></a>00806 <span class="comment">/* (xa - xc) - (yb-yd) */</span>
809 <a name="l00807"></a>00807 r1 = r2 - t1;
810 <a name="l00808"></a>00808
811 <a name="l00809"></a>00809 <span class="comment">/* (xa - xc) + (yb-yd) */</span>
812 <a name="l00810"></a>00810 r2 = r2 + t1;
813 <a name="l00811"></a>00811
814 <a name="l00812"></a>00812 <span class="comment">/* (ya - yc) + (xb-xd) */</span>
815 <a name="l00813"></a>00813 s1 = s2 + t2;
816 <a name="l00814"></a>00814
817 <a name="l00815"></a>00815 <span class="comment">/* (ya - yc) - (xb-xd) */</span>
818 <a name="l00816"></a>00816 s2 = s2 - t2;
819 <a name="l00817"></a>00817
820 <a name="l00818"></a>00818 <span class="comment">/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */</span>
821 <a name="l00819"></a>00819 pSrc[2u * i2] = r1;
822 <a name="l00820"></a>00820 <span class="comment">/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */</span>
823 <a name="l00821"></a>00821 pSrc[(2u * i2) + 1u] = s1;
824 <a name="l00822"></a>00822
825 <a name="l00823"></a>00823 <span class="comment">/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */</span>
826 <a name="l00824"></a>00824 pSrc[2u * i3] = r2;
827 <a name="l00825"></a>00825 <span class="comment">/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */</span>
828 <a name="l00826"></a>00826 pSrc[(2u * i3) + 1u] = s2;
829 <a name="l00827"></a>00827
830 <a name="l00828"></a>00828 }
831 <a name="l00829"></a>00829
832 <a name="l00830"></a>00830 <span class="comment">/* output is in 11.21(q21) format for the 1024 point */</span>
833 <a name="l00831"></a>00831 <span class="comment">/* output is in 9.23(q23) format for the 256 point */</span>
834 <a name="l00832"></a>00832 <span class="comment">/* output is in 7.25(q25) format for the 64 point */</span>
835 <a name="l00833"></a>00833 <span class="comment">/* output is in 5.27(q27) format for the 16 point */</span>
836 <a name="l00834"></a>00834
837 <a name="l00835"></a>00835 <span class="comment">/* End of last stage process */</span>
838 <a name="l00836"></a>00836 }
839 <a name="l00837"></a>00837
840 <a name="l00838"></a>00838
841 <a name="l00839"></a>00839 <span class="comment">/* </span>
842 <a name="l00840"></a>00840 <span class="comment"> * @brief In-place bit reversal function. </span>
843 <a name="l00841"></a>00841 <span class="comment"> * @param[in, out] *pSrc points to the in-place buffer of Q31 data type. </span>
844 <a name="l00842"></a>00842 <span class="comment"> * @param[in] fftLen length of the FFT. </span>
845 <a name="l00843"></a>00843 <span class="comment"> * @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table </span>
846 <a name="l00844"></a>00844 <span class="comment"> * @param[in] *pBitRevTab points to bit reversal table. </span>
847 <a name="l00845"></a>00845 <span class="comment"> * @return none. </span>
848 <a name="l00846"></a>00846 <span class="comment"> */</span>
849 <a name="l00847"></a>00847
850 <a name="l00848"></a><a class="code" href="arm__math_8h.html#a3fab577d25c3a517973c8c214f66f268">00848</a> <span class="keywordtype">void</span> <a class="code" href="arm__cfft__radix4__q31_8c.html#a27618705158b5c42db5fb0a381f8efc1" title="In-place bit reversal function.">arm_bitreversal_q31</a>(
851 <a name="l00849"></a>00849 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> * pSrc,
852 <a name="l00850"></a>00850 uint32_t fftLen,
853 <a name="l00851"></a>00851 uint16_t bitRevFactor,
854 <a name="l00852"></a>00852 uint16_t * pBitRevTable)
855 <a name="l00853"></a>00853 {
856 <a name="l00854"></a>00854 uint32_t fftLenBy2, fftLenBy2p1, i, j;
857 <a name="l00855"></a>00855 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> in;
858 <a name="l00856"></a>00856
859 <a name="l00857"></a>00857 <span class="comment">/* Initializations */</span>
860 <a name="l00858"></a>00858 j = 0u;
861 <a name="l00859"></a>00859 fftLenBy2 = fftLen / 2u;
862 <a name="l00860"></a>00860 fftLenBy2p1 = (fftLen / 2u) + 1u;
863 <a name="l00861"></a>00861
864 <a name="l00862"></a>00862 <span class="comment">/* Bit Reversal Implementation */</span>
865 <a name="l00863"></a>00863 <span class="keywordflow">for</span> (i = 0u; i <= (fftLenBy2 - 2u); i += 2u)
866 <a name="l00864"></a>00864 {
867 <a name="l00865"></a>00865 <span class="keywordflow">if</span>(i < j)
868 <a name="l00866"></a>00866 {
869 <a name="l00867"></a>00867 <span class="comment">/* pSrc[i] <-> pSrc[j]; */</span>
870 <a name="l00868"></a>00868 in = pSrc[2u * i];
871 <a name="l00869"></a>00869 pSrc[2u * i] = pSrc[2u * j];
872 <a name="l00870"></a>00870 pSrc[2u * j] = in;
873 <a name="l00871"></a>00871
874 <a name="l00872"></a>00872 <span class="comment">/* pSrc[i+1u] <-> pSrc[j+1u] */</span>
875 <a name="l00873"></a>00873 in = pSrc[(2u * i) + 1u];
876 <a name="l00874"></a>00874 pSrc[(2u * i) + 1u] = pSrc[(2u * j) + 1u];
877 <a name="l00875"></a>00875 pSrc[(2u * j) + 1u] = in;
878 <a name="l00876"></a>00876
879 <a name="l00877"></a>00877 <span class="comment">/* pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */</span>
880 <a name="l00878"></a>00878 in = pSrc[2u * (i + fftLenBy2p1)];
881 <a name="l00879"></a>00879 pSrc[2u * (i + fftLenBy2p1)] = pSrc[2u * (j + fftLenBy2p1)];
882 <a name="l00880"></a>00880 pSrc[2u * (j + fftLenBy2p1)] = in;
883 <a name="l00881"></a>00881
884 <a name="l00882"></a>00882 <span class="comment">/* pSrc[i+fftLenBy2p1+1u] <-> pSrc[j+fftLenBy2p1+1u] */</span>
885 <a name="l00883"></a>00883 in = pSrc[(2u * (i + fftLenBy2p1)) + 1u];
886 <a name="l00884"></a>00884 pSrc[(2u * (i + fftLenBy2p1)) + 1u] =
887 <a name="l00885"></a>00885 pSrc[(2u * (j + fftLenBy2p1)) + 1u];
888 <a name="l00886"></a>00886 pSrc[(2u * (j + fftLenBy2p1)) + 1u] = in;
889 <a name="l00887"></a>00887
890 <a name="l00888"></a>00888 }
891 <a name="l00889"></a>00889
892 <a name="l00890"></a>00890 <span class="comment">/* pSrc[i+1u] <-> pSrc[j+1u] */</span>
893 <a name="l00891"></a>00891 in = pSrc[2u * (i + 1u)];
894 <a name="l00892"></a>00892 pSrc[2u * (i + 1u)] = pSrc[2u * (j + fftLenBy2)];
895 <a name="l00893"></a>00893 pSrc[2u * (j + fftLenBy2)] = in;
896 <a name="l00894"></a>00894
897 <a name="l00895"></a>00895 <span class="comment">/* pSrc[i+2u] <-> pSrc[j+2u] */</span>
898 <a name="l00896"></a>00896 in = pSrc[(2u * (i + 1u)) + 1u];
899 <a name="l00897"></a>00897 pSrc[(2u * (i + 1u)) + 1u] = pSrc[(2u * (j + fftLenBy2)) + 1u];
900 <a name="l00898"></a>00898 pSrc[(2u * (j + fftLenBy2)) + 1u] = in;
901 <a name="l00899"></a>00899
902 <a name="l00900"></a>00900 <span class="comment">/* Reading the index for the bit reversal */</span>
903 <a name="l00901"></a>00901 j = *pBitRevTable;
904 <a name="l00902"></a>00902
905 <a name="l00903"></a>00903 <span class="comment">/* Updating the bit reversal index depending on the fft length */</span>
906 <a name="l00904"></a>00904 pBitRevTable += bitRevFactor;
907 <a name="l00905"></a>00905 }
908 <a name="l00906"></a>00906 }
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