1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=9"/>
<title>Least Mean Square (LMS) Filters</title>
<title>CMSIS-DSP: Least Mean Square (LMS) Filters</title>
<link href="tabs.css" rel="stylesheet" type="text/css"/>
<link href="cmsis.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="dynsections.js"></script>
<script type="text/javascript" src="printComponentTabs.js"></script>
<link href="navtree.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="resize.js"></script>
<script type="text/javascript" src="navtree.js"></script>
<script type="text/javascript">
$(document).ready(initResizable);
$(window).load(resizeHeight);
</script>
<link href="search/search.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="search/search.js"></script>
<script type="text/javascript">
$(document).ready(function() { searchBox.OnSelectItem(0); });
</script>
</head>
<body>
<div id="top"><!-- do not remove this div, it is closed by doxygen! -->
<div id="titlearea">
<table cellspacing="0" cellpadding="0">
<tbody>
<tr style="height: 46px;">
<td id="projectlogo"><img alt="Logo" src="CMSIS_Logo_Final.png"/></td>
<td style="padding-left: 0.5em;">
<div id="projectname">CMSIS-DSP
 <span id="projectnumber">Version 1.7.0</span>
</div>
<div id="projectbrief">CMSIS DSP Software Library</div>
</td>
</tr>
</tbody>
</table>
</div>
<!-- end header part -->
<div id="CMSISnav" class="tabs1">
<ul class="tablist">
<script type="text/javascript">
<!--
writeComponentTabs.call(this);
//-->
</script>
</ul>
</div>
<!-- Generated by Doxygen 1.8.6 -->
<script type="text/javascript">
var searchBox = new SearchBox("searchBox", "search",false,'Search');
</script>
<div id="navrow1" class="tabs">
<ul class="tablist">
<li><a href="index.html"><span>Main Page</span></a></li>
<li><a href="pages.html"><span>Usage and Description</span></a></li>
<li><a href="modules.html"><span>Reference</span></a></li>
<li>
<div id="MSearchBox" class="MSearchBoxInactive">
<span class="left">
<img id="MSearchSelect" src="search/mag_sel.png"
onmouseover="return searchBox.OnSearchSelectShow()"
onmouseout="return searchBox.OnSearchSelectHide()"
alt=""/>
<input type="text" id="MSearchField" value="Search" accesskey="S"
onfocus="searchBox.OnSearchFieldFocus(true)"
onblur="searchBox.OnSearchFieldFocus(false)"
onkeyup="searchBox.OnSearchFieldChange(event)"/>
</span><span class="right">
<a id="MSearchClose" href="javascript:searchBox.CloseResultsWindow()"><img id="MSearchCloseImg" border="0" src="search/close.png" alt=""/></a>
</span>
</div>
</li>
</ul>
</div>
</div><!-- top -->
<div id="side-nav" class="ui-resizable side-nav-resizable">
<div id="nav-tree">
<div id="nav-tree-contents">
<div id="nav-sync" class="sync"></div>
</div>
</div>
<div id="splitbar" style="-moz-user-select:none;"
class="ui-resizable-handle">
</div>
</div>
<script type="text/javascript">
$(document).ready(function(){initNavTree('group__LMS.html','');});
</script>
<div id="doc-content">
<!-- window showing the filter options -->
<div id="MSearchSelectWindow"
onmouseover="return searchBox.OnSearchSelectShow()"
onmouseout="return searchBox.OnSearchSelectHide()"
onkeydown="return searchBox.OnSearchSelectKey(event)">
<a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(0)"><span class="SelectionMark"> </span>All</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(1)"><span class="SelectionMark"> </span>Data Structures</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(2)"><span class="SelectionMark"> </span>Files</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(3)"><span class="SelectionMark"> </span>Functions</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(4)"><span class="SelectionMark"> </span>Variables</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(5)"><span class="SelectionMark"> </span>Typedefs</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(6)"><span class="SelectionMark"> </span>Enumerations</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(7)"><span class="SelectionMark"> </span>Enumerator</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(8)"><span class="SelectionMark"> </span>Macros</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(9)"><span class="SelectionMark"> </span>Groups</a><a class="SelectItem" href="javascript:void(0)" onclick="searchBox.OnSelectItem(10)"><span class="SelectionMark"> </span>Pages</a></div>
<!-- iframe showing the search results (closed by default) -->
<div id="MSearchResultsWindow">
<iframe src="javascript:void(0)" frameborder="0"
name="MSearchResults" id="MSearchResults">
</iframe>
</div>
<div class="header">
<div class="summary">
<a href="#func-members">Functions</a> </div>
<div class="headertitle">
<div class="title">Least Mean Square (LMS) Filters<div class="ingroups"><a class="el" href="group__groupFilters.html">Filtering Functions</a></div></div> </div>
</div><!--header-->
<div class="contents">
<table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:gac518f7acd1778a8ee90e81c421cfbb90"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="group__LMS.html#gac518f7acd1778a8ee90e81c421cfbb90">arm_lms_f32</a> (const <a class="el" href="structarm__lms__instance__f32.html">arm_lms_instance_f32</a> *S, const <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pSrc, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pRef, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pOut, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pErr, uint32_t <a class="el" href="arm__variance__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>)</td></tr>
<tr class="memdesc:gac518f7acd1778a8ee90e81c421cfbb90"><td class="mdescLeft"> </td><td class="mdescRight">Processing function for floating-point LMS filter. <a href="#gac518f7acd1778a8ee90e81c421cfbb90">More...</a><br/></td></tr>
<tr class="separator:gac518f7acd1778a8ee90e81c421cfbb90"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga9fc7adca0966ff2cec1746fca8364cee"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="group__LMS.html#ga9fc7adca0966ff2cec1746fca8364cee">arm_lms_init_f32</a> (<a class="el" href="structarm__lms__instance__f32.html">arm_lms_instance_f32</a> *S, uint16_t numTaps, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pCoeffs, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> *pState, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> mu, uint32_t <a class="el" href="arm__variance__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>)</td></tr>
<tr class="memdesc:ga9fc7adca0966ff2cec1746fca8364cee"><td class="mdescLeft"> </td><td class="mdescRight">Initialization function for floating-point LMS filter. <a href="#ga9fc7adca0966ff2cec1746fca8364cee">More...</a><br/></td></tr>
<tr class="separator:ga9fc7adca0966ff2cec1746fca8364cee"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga9544cc26f18cd4465cfbed371be822b3"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="group__LMS.html#ga9544cc26f18cd4465cfbed371be822b3">arm_lms_init_q15</a> (<a class="el" href="structarm__lms__instance__q15.html">arm_lms_instance_q15</a> *S, uint16_t numTaps, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pCoeffs, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pState, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> mu, uint32_t <a class="el" href="arm__variance__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>, uint32_t postShift)</td></tr>
<tr class="memdesc:ga9544cc26f18cd4465cfbed371be822b3"><td class="mdescLeft"> </td><td class="mdescRight">Initialization function for the Q15 LMS filter. <a href="#ga9544cc26f18cd4465cfbed371be822b3">More...</a><br/></td></tr>
<tr class="separator:ga9544cc26f18cd4465cfbed371be822b3"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga8d4bc251169f4b102355097a9f7530d6"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="group__LMS.html#ga8d4bc251169f4b102355097a9f7530d6">arm_lms_init_q31</a> (<a class="el" href="structarm__lms__instance__q31.html">arm_lms_instance_q31</a> *S, uint16_t numTaps, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pCoeffs, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pState, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> mu, uint32_t <a class="el" href="arm__variance__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>, uint32_t postShift)</td></tr>
<tr class="memdesc:ga8d4bc251169f4b102355097a9f7530d6"><td class="mdescLeft"> </td><td class="mdescRight">Initialization function for Q31 LMS filter. <a href="#ga8d4bc251169f4b102355097a9f7530d6">More...</a><br/></td></tr>
<tr class="separator:ga8d4bc251169f4b102355097a9f7530d6"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga12fd93f61401b365789cdfd5dca07e5b"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="group__LMS.html#ga12fd93f61401b365789cdfd5dca07e5b">arm_lms_q15</a> (const <a class="el" href="structarm__lms__instance__q15.html">arm_lms_instance_q15</a> *S, const <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pSrc, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pRef, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pOut, <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> *pErr, uint32_t <a class="el" href="arm__variance__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>)</td></tr>
<tr class="memdesc:ga12fd93f61401b365789cdfd5dca07e5b"><td class="mdescLeft"> </td><td class="mdescRight">Processing function for Q15 LMS filter. <a href="#ga12fd93f61401b365789cdfd5dca07e5b">More...</a><br/></td></tr>
<tr class="separator:ga12fd93f61401b365789cdfd5dca07e5b"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga69c9c64338c067f1fb4990dcdc8c143f"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="group__LMS.html#ga69c9c64338c067f1fb4990dcdc8c143f">arm_lms_q31</a> (const <a class="el" href="structarm__lms__instance__q31.html">arm_lms_instance_q31</a> *S, const <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pSrc, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pRef, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pOut, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> *pErr, uint32_t <a class="el" href="arm__variance__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>)</td></tr>
<tr class="memdesc:ga69c9c64338c067f1fb4990dcdc8c143f"><td class="mdescLeft"> </td><td class="mdescRight">Processing function for Q31 LMS filter. <a href="#ga69c9c64338c067f1fb4990dcdc8c143f">More...</a><br/></td></tr>
<tr class="separator:ga69c9c64338c067f1fb4990dcdc8c143f"><td class="memSeparator" colspan="2"> </td></tr>
</table>
<a name="details" id="details"></a><h2 class="groupheader">Description</h2>
<p>LMS filters are a class of adaptive filters that are able to "learn" an unknown transfer functions. LMS filters use a gradient descent method in which the filter coefficients are updated based on the instantaneous error signal. Adaptive filters are often used in communication systems, equalizers, and noise removal. The CMSIS DSP Library contains LMS filter functions that operate on Q15, Q31, and floating-point data types. The library also contains normalized LMS filters in which the filter coefficient adaptation is indepedent of the level of the input signal.</p>
<p>An LMS filter consists of two components as shown below. The first component is a standard transversal or FIR filter. The second component is a coefficient update mechanism. The LMS filter has two input signals. The "input" feeds the FIR filter while the "reference input" corresponds to the desired output of the FIR filter. That is, the FIR filter coefficients are updated so that the output of the FIR filter matches the reference input. The filter coefficient update mechanism is based on the difference between the FIR filter output and the reference input. This "error signal" tends towards zero as the filter adapts. The LMS processing functions accept the input and reference input signals and generate the filter output and error signal. </p>
<div class="image">
<img src="LMS.gif" alt="LMS.gif"/>
<div class="caption">
Internal structure of the Least Mean Square filter</div></div>
<p> The functions operate on blocks of data and each call to the function processes <code>blockSize</code> samples through the filter. <code>pSrc</code> points to input signal, <code>pRef</code> points to reference signal, <code>pOut</code> points to output signal and <code>pErr</code> points to error signal. All arrays contain <code>blockSize</code> values.</p>
<p>The functions operate on a block-by-block basis. Internally, the filter coefficients <code>b[n]</code> are updated on a sample-by-sample basis. The convergence of the LMS filter is slower compared to the normalized LMS algorithm.</p>
<dl class="section user"><dt>Algorithm</dt><dd>The output signal <code>y[n]</code> is computed by a standard FIR filter: <pre>
y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1]
</pre></dd></dl>
<dl class="section user"><dt></dt><dd>The error signal equals the difference between the reference signal <code>d[n]</code> and the filter output: <pre>
e[n] = d[n] - y[n].
</pre></dd></dl>
<dl class="section user"><dt></dt><dd>After each sample of the error signal is computed, the filter coefficients <code>b[k]</code> are updated on a sample-by-sample basis: <pre>
b[k] = b[k] + e[n] * mu * x[n-k], for k=0, 1, ..., numTaps-1
</pre> where <code>mu</code> is the step size and controls the rate of coefficient convergence. </dd></dl>
<dl class="section user"><dt></dt><dd>In the APIs, <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>. Coefficients are stored in time reversed order. </dd></dl>
<dl class="section user"><dt></dt><dd><pre>
{b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
</pre> </dd></dl>
<dl class="section user"><dt></dt><dd><code>pState</code> points to a state array of size <code>numTaps + blockSize - 1</code>. Samples in the state buffer are stored in the order: </dd></dl>
<dl class="section user"><dt></dt><dd><pre>
{x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]}
</pre> </dd></dl>
<dl class="section user"><dt></dt><dd>Note that the length of the state buffer exceeds the length of the coefficient array by <code>blockSize-1</code> samples. The increased state buffer length allows circular addressing, which is traditionally used in FIR filters, to be avoided and yields a significant speed improvement. The state variables are updated after each block of data is processed. </dd></dl>
<dl class="section user"><dt>Instance Structure</dt><dd>The coefficients and state variables for a filter are stored together in an instance data structure. A separate instance structure must be defined for each filter and coefficient and state arrays cannot be shared among instances. There are separate instance structure declarations for each of the 3 supported data types.</dd></dl>
<dl class="section user"><dt>Initialization Functions</dt><dd>There is also an associated initialization function for each data type. The initialization function performs the following operations:<ul>
<li>Sets the values of the internal structure fields.</li>
<li>Zeros out the values in the state buffer. To do this manually without calling the init function, assign the follow subfields of the instance structure: numTaps, pCoeffs, mu, postShift (not for f32), pState. Also set all of the values in pState to zero.</li>
</ul>
</dd></dl>
<dl class="section user"><dt></dt><dd>Use of the initialization function is optional. However, if the initialization function is used, then the instance structure cannot be placed into a const data section. To place an instance structure into a const data section, the instance structure must be manually initialized. Set the values in the state buffer to zeros before static initialization. The code below statically initializes each of the 3 different data type filter instance structures <pre>
<a class="el" href="structarm__lms__instance__f32.html" title="Instance structure for the floating-point LMS filter. ">arm_lms_instance_f32</a> S = {numTaps, pState, pCoeffs, mu};
<a class="el" href="structarm__lms__instance__q31.html" title="Instance structure for the Q31 LMS filter. ">arm_lms_instance_q31</a> S = {numTaps, pState, pCoeffs, mu, postShift};
<a class="el" href="structarm__lms__instance__q15.html" title="Instance structure for the Q15 LMS filter. ">arm_lms_instance_q15</a> S = {numTaps, pState, pCoeffs, mu, postShift};
</pre> where <code>numTaps</code> is the number of filter coefficients in the filter; <code>pState</code> is the address of the state buffer; <code>pCoeffs</code> is the address of the coefficient buffer; <code>mu</code> is the step size parameter; and <code>postShift</code> is the shift applied to coefficients.</dd></dl>
<dl class="section user"><dt>Fixed-Point Behavior</dt><dd>Care must be taken when using the Q15 and Q31 versions of the LMS filter. The following issues must be considered:<ul>
<li>Scaling of coefficients</li>
<li>Overflow and saturation</li>
</ul>
</dd></dl>
<dl class="section user"><dt>Scaling of Coefficients</dt><dd>Filter coefficients are represented as fractional values and coefficients are restricted to lie in the range <code>[-1 +1)</code>. The fixed-point functions have an additional scaling parameter <code>postShift</code>. At the output of the filter's accumulator is a shift register which shifts the result by <code>postShift</code> bits. This essentially scales the filter coefficients by <code>2^postShift</code> and allows the filter coefficients to exceed the range <code>[+1 -1)</code>. The value of <code>postShift</code> is set by the user based on the expected gain through the system being modeled.</dd></dl>
<dl class="section user"><dt>Overflow and Saturation</dt><dd>Overflow and saturation behavior of the fixed-point Q15 and Q31 versions are described separately as part of the function specific documentation below. </dd></dl>
<h2 class="groupheader">Function Documentation</h2>
<a class="anchor" id="gac518f7acd1778a8ee90e81c421cfbb90"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_lms_f32 </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="structarm__lms__instance__f32.html">arm_lms_instance_f32</a> * </td>
<td class="paramname"><em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> * </td>
<td class="paramname"><em>pSrc</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> * </td>
<td class="paramname"><em>pRef</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> * </td>
<td class="paramname"><em>pOut</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> * </td>
<td class="paramname"><em>pErr</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>blockSize</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the floating-point LMS filter structure </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pSrc</td><td>points to the block of input data </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pRef</td><td>points to the block of reference data </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">pOut</td><td>points to the block of output data </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">pErr</td><td>points to the block of error data </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">blockSize</td><td>number of samples to process </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none </dd></dl>
</div>
</div>
<a class="anchor" id="ga9fc7adca0966ff2cec1746fca8364cee"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_lms_init_f32 </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structarm__lms__instance__f32.html">arm_lms_instance_f32</a> * </td>
<td class="paramname"><em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint16_t </td>
<td class="paramname"><em>numTaps</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> * </td>
<td class="paramname"><em>pCoeffs</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> * </td>
<td class="paramname"><em>pState</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> </td>
<td class="paramname"><em>mu</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>blockSize</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the floating-point LMS filter structure </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">numTaps</td><td>number of filter coefficients </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pCoeffs</td><td>points to coefficient buffer </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pState</td><td>points to state buffer </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">mu</td><td>step size that controls filter coefficient updates </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">blockSize</td><td>number of samples to process </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none</dd></dl>
<dl class="section user"><dt>Details</dt><dd><code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order: <pre>
{b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
</pre> The initial filter coefficients serve as a starting point for the adaptive filter. <code>pState</code> points to an array of length <code>numTaps+blockSize-1</code> samples, where <code>blockSize</code> is the number of input samples processed by each call to <code><a class="el" href="group__LMS.html#gac518f7acd1778a8ee90e81c421cfbb90" title="Processing function for floating-point LMS filter. ">arm_lms_f32()</a></code>. </dd></dl>
</div>
</div>
<a class="anchor" id="ga9544cc26f18cd4465cfbed371be822b3"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_lms_init_q15 </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structarm__lms__instance__q15.html">arm_lms_instance_q15</a> * </td>
<td class="paramname"><em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint16_t </td>
<td class="paramname"><em>numTaps</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> * </td>
<td class="paramname"><em>pCoeffs</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> * </td>
<td class="paramname"><em>pState</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> </td>
<td class="paramname"><em>mu</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>blockSize</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>postShift</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the Q15 LMS filter structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">numTaps</td><td>number of filter coefficients. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pCoeffs</td><td>points to coefficient buffer. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pState</td><td>points to state buffer. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">mu</td><td>step size that controls filter coefficient updates. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">blockSize</td><td>number of samples to process. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">postShift</td><td>bit shift applied to coefficients. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none</dd></dl>
<dl class="section user"><dt>Details</dt><dd><code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order: <pre>
{b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
</pre> The initial filter coefficients serve as a starting point for the adaptive filter. <code>pState</code> points to the array of state variables and size of array is <code>numTaps+blockSize-1</code> samples, where <code>blockSize</code> is the number of input samples processed by each call to <code><a class="el" href="group__LMS.html#ga12fd93f61401b365789cdfd5dca07e5b" title="Processing function for Q15 LMS filter. ">arm_lms_q15()</a></code>. </dd></dl>
</div>
</div>
<a class="anchor" id="ga8d4bc251169f4b102355097a9f7530d6"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_lms_init_q31 </td>
<td>(</td>
<td class="paramtype"><a class="el" href="structarm__lms__instance__q31.html">arm_lms_instance_q31</a> * </td>
<td class="paramname"><em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint16_t </td>
<td class="paramname"><em>numTaps</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> * </td>
<td class="paramname"><em>pCoeffs</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> * </td>
<td class="paramname"><em>pState</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> </td>
<td class="paramname"><em>mu</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>blockSize</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>postShift</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the Q31 LMS filter structure </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">numTaps</td><td>number of filter coefficients </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pCoeffs</td><td>points to coefficient buffer </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pState</td><td>points to state buffer </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">mu</td><td>step size that controls filter coefficient updates </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">blockSize</td><td>number of samples to process </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">postShift</td><td>bit shift applied to coefficients </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none</dd></dl>
<dl class="section user"><dt>Details</dt><dd><code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order: <pre>
{b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
</pre> The initial filter coefficients serve as a starting point for the adaptive filter. <code>pState</code> points to an array of length <code>numTaps+blockSize-1</code> samples, where <code>blockSize</code> is the number of input samples processed by each call to <code><a class="el" href="group__LMS.html#ga69c9c64338c067f1fb4990dcdc8c143f" title="Processing function for Q31 LMS filter. ">arm_lms_q31()</a></code>. </dd></dl>
</div>
</div>
<a class="anchor" id="ga12fd93f61401b365789cdfd5dca07e5b"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_lms_q15 </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="structarm__lms__instance__q15.html">arm_lms_instance_q15</a> * </td>
<td class="paramname"><em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> * </td>
<td class="paramname"><em>pSrc</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> * </td>
<td class="paramname"><em>pRef</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> * </td>
<td class="paramname"><em>pOut</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> * </td>
<td class="paramname"><em>pErr</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>blockSize</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the Q15 LMS filter structure </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pSrc</td><td>points to the block of input data </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pRef</td><td>points to the block of reference data </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">pOut</td><td>points to the block of output data </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">pErr</td><td>points to the block of error data </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">blockSize</td><td>number of samples to process </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none</dd></dl>
<dl class="section user"><dt>Scaling and Overflow Behavior</dt><dd>The function is implemented using an internal 64-bit accumulator. Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result. The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format. There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved. After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits. Lastly, the accumulator is saturated to yield a result in 1.15 format. </dd></dl>
<dl class="section user"><dt></dt><dd>In this filter, filter coefficients are updated for each sample and the updation of filter cofficients are saturted. </dd></dl>
</div>
</div>
<a class="anchor" id="ga69c9c64338c067f1fb4990dcdc8c143f"></a>
<div class="memitem">
<div class="memproto">
<table class="memname">
<tr>
<td class="memname">void arm_lms_q31 </td>
<td>(</td>
<td class="paramtype">const <a class="el" href="structarm__lms__instance__q31.html">arm_lms_instance_q31</a> * </td>
<td class="paramname"><em>S</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">const <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> * </td>
<td class="paramname"><em>pSrc</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> * </td>
<td class="paramname"><em>pRef</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> * </td>
<td class="paramname"><em>pOut</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> * </td>
<td class="paramname"><em>pErr</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">uint32_t </td>
<td class="paramname"><em>blockSize</em> </td>
</tr>
<tr>
<td></td>
<td>)</td>
<td></td><td></td>
</tr>
</table>
</div><div class="memdoc">
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">S</td><td>points to an instance of the Q31 LMS filter structure. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pSrc</td><td>points to the block of input data. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">pRef</td><td>points to the block of reference data. </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">pOut</td><td>points to the block of output data. </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">pErr</td><td>points to the block of error data. </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">blockSize</td><td>number of samples to process. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>none</dd></dl>
<dl class="section user"><dt>Scaling and Overflow Behavior</dt><dd>The function is implemented using an internal 64-bit accumulator. The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit. Thus, if the accumulator result overflows it wraps around rather than clips. In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits. The reference signal should not be scaled down. After all multiply-accumulates are performed, the 2.62 accumulator is shifted and saturated to 1.31 format to yield the final result. The output signal and error signal are in 1.31 format. </dd></dl>
<dl class="section user"><dt></dt><dd>In this filter, filter coefficients are updated for each sample and the updation of filter cofficients are saturted. </dd></dl>
</div>
</div>
</div><!-- contents -->
</div><!-- doc-content -->
<!-- start footer part -->
<div id="nav-path" class="navpath"><!-- id is needed for treeview function! -->
<ul>
<li class="footer">Generated on Wed Jul 10 2019 15:20:40 for CMSIS-DSP Version 1.7.0 by Arm Ltd. All rights reserved.
<!--
<a href="http://www.doxygen.org/index.html">
<img class="footer" src="doxygen.png" alt="doxygen"/></a> 1.8.6
-->
</li>
</ul>
</div>
</body>
</html>
|
