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49 <div class="headertitle">
50 <h1>arm_fir_decimate_fast_q31.c</h1> </div>
52 <div class="contents">
53 <a href="arm__fir__decimate__fast__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_fir_decimate_fast_q31.c </span>
61 <a name="l00009"></a>00009 <span class="comment">* </span>
62 <a name="l00010"></a>00010 <span class="comment">* Description: Fast Q31 FIR Decimator. </span>
63 <a name="l00011"></a>00011 <span class="comment">* </span>
64 <a name="l00012"></a>00012 <span class="comment">* Target Processor: Cortex-M4/Cortex-M3</span>
65 <a name="l00013"></a>00013 <span class="comment">* </span>
66 <a name="l00014"></a>00014 <span class="comment">* Version 1.0.10 2011/7/15 </span>
67 <a name="l00015"></a>00015 <span class="comment">* Big Endian support added and Merged M0 and M3/M4 Source code. </span>
68 <a name="l00016"></a>00016 <span class="comment">* </span>
69 <a name="l00017"></a>00017 <span class="comment">* Version 1.0.3 2010/11/29 </span>
70 <a name="l00018"></a>00018 <span class="comment">* Re-organized the CMSIS folders and updated documentation. </span>
71 <a name="l00019"></a>00019 <span class="comment">* </span>
72 <a name="l00020"></a>00020 <span class="comment">* Version 1.0.2 2010/11/11 </span>
73 <a name="l00021"></a>00021 <span class="comment">* Documentation updated. </span>
74 <a name="l00022"></a>00022 <span class="comment">* </span>
75 <a name="l00023"></a>00023 <span class="comment">* Version 1.0.1 2010/10/05 </span>
76 <a name="l00024"></a>00024 <span class="comment">* Production release and review comments incorporated. </span>
77 <a name="l00025"></a>00025 <span class="comment">* </span>
78 <a name="l00026"></a>00026 <span class="comment">* Version 1.0.0 2010/09/20 </span>
79 <a name="l00027"></a>00027 <span class="comment">* Production release and review comments incorporated. </span>
80 <a name="l00028"></a>00028 <span class="comment">* -------------------------------------------------------------------- */</span>
81 <a name="l00029"></a>00029
82 <a name="l00030"></a>00030 <span class="preprocessor">#include "<a class="code" href="arm__math_8h.html">arm_math.h</a>"</span>
83 <a name="l00031"></a>00031
84 <a name="l00065"></a><a class="code" href="group___f_i_r__decimate.html#ga3c18cc3d0548a410c577f1bead9582b7">00065</a> <span class="keywordtype">void</span> <a class="code" href="group___f_i_r__decimate.html#ga3c18cc3d0548a410c577f1bead9582b7" title="Processing function for the Q31 FIR decimator (fast variant) for Cortex-M3 and Cortex-M4.">arm_fir_decimate_fast_q31</a>(
85 <a name="l00066"></a>00066 <a class="code" href="structarm__fir__decimate__instance__q31.html" title="Instance structure for the Q31 FIR decimator.">arm_fir_decimate_instance_q31</a> * S,
86 <a name="l00067"></a>00067 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> * pSrc,
87 <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> * pDst,
88 <a name="l00069"></a>00069 uint32_t <a class="code" href="arm__fir__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>)
89 <a name="l00070"></a>00070 {
90 <a name="l00071"></a>00071 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *pState = S-><a class="code" href="structarm__fir__decimate__instance__q31.html#a0ef0ef9e265f7ab873cfc6daa7593fdb">pState</a>; <span class="comment">/* State pointer */</span>
91 <a name="l00072"></a>00072 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *pCoeffs = S-><a class="code" href="structarm__fir__decimate__instance__q31.html#a030d0391538c2481c5b348fd09a952ff">pCoeffs</a>; <span class="comment">/* Coefficient pointer */</span>
92 <a name="l00073"></a>00073 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *pStateCurnt; <span class="comment">/* Points to the current sample of the state */</span>
93 <a name="l00074"></a>00074 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> x0, c0; <span class="comment">/* Temporary variables to hold state and coefficient values */</span>
94 <a name="l00075"></a>00075 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *px; <span class="comment">/* Temporary pointers for state buffer */</span>
95 <a name="l00076"></a>00076 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> *pb; <span class="comment">/* Temporary pointers for coefficient buffer */</span>
96 <a name="l00077"></a>00077 <a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a> sum0; <span class="comment">/* Accumulator */</span>
97 <a name="l00078"></a>00078 uint32_t numTaps = S-><a class="code" href="structarm__fir__decimate__instance__q31.html#a37915d42b0dc5e3057ebe83110798482">numTaps</a>; <span class="comment">/* Number of taps */</span>
98 <a name="l00079"></a>00079 uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S-><a class="code" href="structarm__fir__decimate__instance__q31.html#ad3d6936c36303b30dd38f1eddf248ae5">M</a>; <span class="comment">/* Loop counters */</span>
99 <a name="l00080"></a>00080
100 <a name="l00081"></a>00081
101 <a name="l00082"></a>00082 <span class="comment">/* S->pState buffer contains previous frame (numTaps - 1) samples */</span>
102 <a name="l00083"></a>00083 <span class="comment">/* pStateCurnt points to the location where the new input data should be written */</span>
103 <a name="l00084"></a>00084 pStateCurnt = S-><a class="code" href="structarm__fir__decimate__instance__q31.html#a0ef0ef9e265f7ab873cfc6daa7593fdb">pState</a> + (numTaps - 1u);
104 <a name="l00085"></a>00085
105 <a name="l00086"></a>00086 <span class="comment">/* Total number of output samples to be computed */</span>
106 <a name="l00087"></a>00087 blkCnt = outBlockSize;
107 <a name="l00088"></a>00088
108 <a name="l00089"></a>00089 <span class="keywordflow">while</span>(blkCnt > 0u)
109 <a name="l00090"></a>00090 {
110 <a name="l00091"></a>00091 <span class="comment">/* Copy decimation factor number of new input samples into the state buffer */</span>
111 <a name="l00092"></a>00092 i = S-><a class="code" href="structarm__fir__decimate__instance__q31.html#ad3d6936c36303b30dd38f1eddf248ae5">M</a>;
112 <a name="l00093"></a>00093
113 <a name="l00094"></a>00094 <span class="keywordflow">do</span>
114 <a name="l00095"></a>00095 {
115 <a name="l00096"></a>00096 *pStateCurnt++ = *pSrc++;
116 <a name="l00097"></a>00097
117 <a name="l00098"></a>00098 } <span class="keywordflow">while</span>(--i);
118 <a name="l00099"></a>00099
119 <a name="l00100"></a>00100 <span class="comment">/* Set accumulator to zero */</span>
120 <a name="l00101"></a>00101 sum0 = 0;
121 <a name="l00102"></a>00102
122 <a name="l00103"></a>00103 <span class="comment">/* Initialize state pointer */</span>
123 <a name="l00104"></a>00104 px = pState;
124 <a name="l00105"></a>00105
125 <a name="l00106"></a>00106 <span class="comment">/* Initialize coeff pointer */</span>
126 <a name="l00107"></a>00107 pb = pCoeffs;
127 <a name="l00108"></a>00108
128 <a name="l00109"></a>00109 <span class="comment">/* Loop unrolling. Process 4 taps at a time. */</span>
129 <a name="l00110"></a>00110 tapCnt = numTaps >> 2;
130 <a name="l00111"></a>00111
131 <a name="l00112"></a>00112 <span class="comment">/* Loop over the number of taps. Unroll by a factor of 4. </span>
132 <a name="l00113"></a>00113 <span class="comment"> ** Repeat until we've computed numTaps-4 coefficients. */</span>
133 <a name="l00114"></a>00114 <span class="keywordflow">while</span>(tapCnt > 0u)
134 <a name="l00115"></a>00115 {
135 <a name="l00116"></a>00116 <span class="comment">/* Read the b[numTaps-1] coefficient */</span>
136 <a name="l00117"></a>00117 c0 = *(pb++);
137 <a name="l00118"></a>00118
138 <a name="l00119"></a>00119 <span class="comment">/* Read x[n-numTaps-1] sample */</span>
139 <a name="l00120"></a>00120 x0 = *(px++);
140 <a name="l00121"></a>00121
141 <a name="l00122"></a>00122 <span class="comment">/* Perform the multiply-accumulate */</span>
142 <a name="l00123"></a>00123 sum0 = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) ((((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) x0 * c0) + (sum0 << 32)) >> 32);
143 <a name="l00124"></a>00124
144 <a name="l00125"></a>00125 <span class="comment">/* Read the b[numTaps-2] coefficient */</span>
145 <a name="l00126"></a>00126 c0 = *(pb++);
146 <a name="l00127"></a>00127
147 <a name="l00128"></a>00128 <span class="comment">/* Read x[n-numTaps-2] sample */</span>
148 <a name="l00129"></a>00129 x0 = *(px++);
149 <a name="l00130"></a>00130
150 <a name="l00131"></a>00131 <span class="comment">/* Perform the multiply-accumulate */</span>
151 <a name="l00132"></a>00132 sum0 = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) ((((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) x0 * c0) + (sum0 << 32)) >> 32);
152 <a name="l00133"></a>00133
153 <a name="l00134"></a>00134 <span class="comment">/* Read the b[numTaps-3] coefficient */</span>
154 <a name="l00135"></a>00135 c0 = *(pb++);
155 <a name="l00136"></a>00136
156 <a name="l00137"></a>00137 <span class="comment">/* Read x[n-numTaps-3] sample */</span>
157 <a name="l00138"></a>00138 x0 = *(px++);
158 <a name="l00139"></a>00139
159 <a name="l00140"></a>00140 <span class="comment">/* Perform the multiply-accumulate */</span>
160 <a name="l00141"></a>00141 sum0 = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) ((((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) x0 * c0) + (sum0 << 32)) >> 32);
161 <a name="l00142"></a>00142
162 <a name="l00143"></a>00143 <span class="comment">/* Read the b[numTaps-4] coefficient */</span>
163 <a name="l00144"></a>00144 c0 = *(pb++);
164 <a name="l00145"></a>00145
165 <a name="l00146"></a>00146 <span class="comment">/* Read x[n-numTaps-4] sample */</span>
166 <a name="l00147"></a>00147 x0 = *(px++);
167 <a name="l00148"></a>00148
168 <a name="l00149"></a>00149 <span class="comment">/* Perform the multiply-accumulate */</span>
169 <a name="l00150"></a>00150 sum0 = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) ((((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) x0 * c0) + (sum0 << 32)) >> 32);
170 <a name="l00151"></a>00151
171 <a name="l00152"></a>00152 <span class="comment">/* Decrement the loop counter */</span>
172 <a name="l00153"></a>00153 tapCnt--;
173 <a name="l00154"></a>00154 }
174 <a name="l00155"></a>00155
175 <a name="l00156"></a>00156 <span class="comment">/* If the filter length is not a multiple of 4, compute the remaining filter taps */</span>
176 <a name="l00157"></a>00157 tapCnt = numTaps % 0x4u;
177 <a name="l00158"></a>00158
178 <a name="l00159"></a>00159 <span class="keywordflow">while</span>(tapCnt > 0u)
179 <a name="l00160"></a>00160 {
180 <a name="l00161"></a>00161 <span class="comment">/* Read coefficients */</span>
181 <a name="l00162"></a>00162 c0 = *(pb++);
182 <a name="l00163"></a>00163
183 <a name="l00164"></a>00164 <span class="comment">/* Fetch 1 state variable */</span>
184 <a name="l00165"></a>00165 x0 = *(px++);
185 <a name="l00166"></a>00166
186 <a name="l00167"></a>00167 <span class="comment">/* Perform the multiply-accumulate */</span>
187 <a name="l00168"></a>00168 sum0 = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) ((((<a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a>) x0 * c0) + (sum0 << 32)) >> 32);
188 <a name="l00169"></a>00169
189 <a name="l00170"></a>00170 <span class="comment">/* Decrement the loop counter */</span>
190 <a name="l00171"></a>00171 tapCnt--;
191 <a name="l00172"></a>00172 }
192 <a name="l00173"></a>00173
193 <a name="l00174"></a>00174 <span class="comment">/* Advance the state pointer by the decimation factor </span>
194 <a name="l00175"></a>00175 <span class="comment"> * to process the next group of decimation factor number samples */</span>
195 <a name="l00176"></a>00176 pState = pState + S-><a class="code" href="structarm__fir__decimate__instance__q31.html#ad3d6936c36303b30dd38f1eddf248ae5">M</a>;
196 <a name="l00177"></a>00177
197 <a name="l00178"></a>00178 <span class="comment">/* The result is in the accumulator, store in the destination buffer. */</span>
198 <a name="l00179"></a>00179 *pDst++ = (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) (sum0 << 1);
199 <a name="l00180"></a>00180
200 <a name="l00181"></a>00181 <span class="comment">/* Decrement the loop counter */</span>
201 <a name="l00182"></a>00182 blkCnt--;
202 <a name="l00183"></a>00183 }
203 <a name="l00184"></a>00184
204 <a name="l00185"></a>00185 <span class="comment">/* Processing is complete. </span>
205 <a name="l00186"></a>00186 <span class="comment"> ** Now copy the last numTaps - 1 samples to the satrt of the state buffer. </span>
206 <a name="l00187"></a>00187 <span class="comment"> ** This prepares the state buffer for the next function call. */</span>
207 <a name="l00188"></a>00188
208 <a name="l00189"></a>00189 <span class="comment">/* Points to the start of the state buffer */</span>
209 <a name="l00190"></a>00190 pStateCurnt = S-><a class="code" href="structarm__fir__decimate__instance__q31.html#a0ef0ef9e265f7ab873cfc6daa7593fdb">pState</a>;
210 <a name="l00191"></a>00191
211 <a name="l00192"></a>00192 i = (numTaps - 1u) >> 2u;
212 <a name="l00193"></a>00193
213 <a name="l00194"></a>00194 <span class="comment">/* copy data */</span>
214 <a name="l00195"></a>00195 <span class="keywordflow">while</span>(i > 0u)
215 <a name="l00196"></a>00196 {
216 <a name="l00197"></a>00197 *pStateCurnt++ = *pState++;
217 <a name="l00198"></a>00198 *pStateCurnt++ = *pState++;
218 <a name="l00199"></a>00199 *pStateCurnt++ = *pState++;
219 <a name="l00200"></a>00200 *pStateCurnt++ = *pState++;
220 <a name="l00201"></a>00201
221 <a name="l00202"></a>00202 <span class="comment">/* Decrement the loop counter */</span>
222 <a name="l00203"></a>00203 i--;
223 <a name="l00204"></a>00204 }
224 <a name="l00205"></a>00205
225 <a name="l00206"></a>00206 i = (numTaps - 1u) % 0x04u;
226 <a name="l00207"></a>00207
227 <a name="l00208"></a>00208 <span class="comment">/* copy data */</span>
228 <a name="l00209"></a>00209 <span class="keywordflow">while</span>(i > 0u)
229 <a name="l00210"></a>00210 {
230 <a name="l00211"></a>00211 *pStateCurnt++ = *pState++;
231 <a name="l00212"></a>00212
232 <a name="l00213"></a>00213 <span class="comment">/* Decrement the loop counter */</span>
233 <a name="l00214"></a>00214 i--;
234 <a name="l00215"></a>00215 }
235 <a name="l00216"></a>00216 }
236 <a name="l00217"></a>00217
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