📄 basic.html
字号:
<html xmlns:v="urn:schemas-microsoft-com:vml"
xmlns:o="urn:schemas-microsoft-com:office:office"
xmlns:w="urn:schemas-microsoft-com:office:word"
xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<meta name=ProgId content=Word.Document>
<meta name=Generator content="Microsoft Word 9">
<meta name=Originator content="Microsoft Word 9">
<link rel=File-List href="./basic_files/filelist.xml">
<link rel=Edit-Time-Data href="./basic_files/editdata.mso">
<link rel=OLE-Object-Data href="./basic_files/oledata.mso">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<title>AT91 SAM7S PWM audio Management Version: 1.0</title>
<!--[if gte mso 9]><xml>
<o:DocumentProperties>
<o:Author>jpperie</o:Author>
<o:LastAuthor>jpperie</o:LastAuthor>
<o:Revision>22</o:Revision>
<o:TotalTime>363</o:TotalTime>
<o:Created>2004-07-13T08:08:00Z</o:Created>
<o:LastSaved>2005-04-27T14:08:00Z</o:LastSaved>
<o:Pages>3</o:Pages>
<o:Words>726</o:Words>
<o:Characters>4139</o:Characters>
<o:Company>ATMEL_ES2</o:Company>
<o:Lines>34</o:Lines>
<o:Paragraphs>8</o:Paragraphs>
<o:CharactersWithSpaces>5082</o:CharactersWithSpaces>
<o:Version>9.2720</o:Version>
</o:DocumentProperties>
</xml><![endif]--><!--[if gte mso 9]><xml>
<w:WordDocument>
<w:Zoom>110</w:Zoom>
</w:WordDocument>
</xml><![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Georgia;
panose-1:2 4 5 2 5 4 5 2 3 3;
mso-font-charset:0;
mso-generic-font-family:roman;
mso-font-pitch:variable;
mso-font-signature:647 0 0 0 159 0;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0cm;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";}
h1
{mso-style-next:Normal;
margin:0cm;
margin-bottom:.0001pt;
text-align:right;
mso-pagination:widow-orphan;
page-break-after:avoid;
mso-outline-level:1;
font-size:12.0pt;
font-family:"Times New Roman";
mso-font-kerning:0pt;
mso-ansi-language:EN-US;
font-weight:bold;}
h2
{mso-style-next:Normal;
margin-top:12.0pt;
margin-right:0cm;
margin-bottom:3.0pt;
margin-left:0cm;
mso-pagination:widow-orphan;
page-break-after:avoid;
mso-outline-level:2;
font-size:14.0pt;
font-family:Arial;
font-weight:bold;
font-style:italic;}
p.MsoBodyTextIndent, li.MsoBodyTextIndent, div.MsoBodyTextIndent
{margin-top:0cm;
margin-right:0cm;
margin-bottom:0cm;
margin-left:36.0pt;
margin-bottom:.0001pt;
text-indent:36.0pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";
mso-ansi-language:EN-US;}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;
text-underline:single;}
a:visited, span.MsoHyperlinkFollowed
{color:blue;
text-decoration:underline;
text-underline:single;}
p
{margin-right:0cm;
mso-margin-top-alt:auto;
mso-margin-bottom-alt:auto;
margin-left:0cm;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";}
@page Section1
{size:595.3pt 841.9pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;
mso-header-margin:35.4pt;
mso-footer-margin:35.4pt;
mso-paper-source:0;}
div.Section1
{page:Section1;}
/* List Definitions */
@list l0
{mso-list-id:856844624;
mso-list-type:hybrid;
mso-list-template-ids:1758633842 468334910 67698691 67698693 67698689 67698691 67698693 67698689 67698691 67698693;}
@list l0:level1
{mso-level-start-at:0;
mso-level-number-format:bullet;
mso-level-text:-;
mso-level-tab-stop:90.0pt;
mso-level-number-position:left;
margin-left:90.0pt;
text-indent:-18.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";
mso-ansi-font-weight:bold;}
@list l1
{mso-list-id:1658682491;
mso-list-type:hybrid;
mso-list-template-ids:436113566 67698705 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l1:level1
{mso-level-start-at:0;
mso-level-text:"%1\)";
mso-level-tab-stop:36.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
ol
{margin-bottom:0cm;}
ul
{margin-bottom:0cm;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1030"/>
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1"/>
</o:shapelayout></xml><![endif]-->
</head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<body bgcolor=white lang=EN-GB link=blue vlink=blue style='tab-interval:36.0pt'>
<div class=Section1>
<h1><span lang=EN-US><!-- ******* title ********** !-->Version: 1.0</span></h1>
<p align=center style='text-align:center'><b><span lang=EN-US style='font-family:
Georgia;mso-ansi-language:EN-US'>AT91 SAM7S PWM</span></b><span lang=EN-US
style='mso-ansi-language:EN-US'><o:p></o:p></span></p>
<p><span lang=EN-US style='mso-ansi-language:EN-US'><!-- ******* Introduction ********** !-->The
goal of this demonstration project is to demonstrate the use of the PWM
channels to implement a voice playback . This example has been build on the <b>AT91SAM7S64-IAR
</b>evaluation kit. <o:p></o:p></span></p>
<p><span lang=EN-US style='mso-ansi-language:EN-US'>Many
embedded-microcontroller applications require generation of analog signals. An
integrated or stand-alone DAC fills the role. However, the SAM7S device does
not feature on-chip DAC but features some PWM channels. PWM channels can be
used for generating the required analog signals. PWM channels can be used to
create both, DC or AC analog signals. This software example shows how to use a
PWM channel to create a sinusoid, a ramp, DC voltage and to output audio
signal. <o:p></o:p></span></p>
<p><span lang=EN-US style='mso-ansi-language:EN-US'>A PWM signal is a digital
signal with a fixed frequency but with a various duty cycle. If the duty cycle
of the PWM signal changes in time and that you are filtering this PWM signal,
the output of the filter will be an analog signal.<o:p></o:p></span></p>
<p align=center style='text-align:center'><span lang=EN-US style='mso-ansi-language:
EN-US'><!--[if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600"
o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f"
stroked="f">
<v:stroke joinstyle="miter"/>
<v:formulas>
<v:f eqn="if lineDrawn pixelLineWidth 0"/>
<v:f eqn="sum @0 1 0"/>
<v:f eqn="sum 0 0 @1"/>
<v:f eqn="prod @2 1 2"/>
<v:f eqn="prod @3 21600 pixelWidth"/>
<v:f eqn="prod @3 21600 pixelHeight"/>
<v:f eqn="sum @0 0 1"/>
<v:f eqn="prod @6 1 2"/>
<v:f eqn="prod @7 21600 pixelWidth"/>
<v:f eqn="sum @8 21600 0"/>
<v:f eqn="prod @7 21600 pixelHeight"/>
<v:f eqn="sum @10 21600 0"/>
</v:formulas>
<v:path o:extrusionok="f" gradientshapeok="t" o:connecttype="rect"/>
<o:lock v:ext="edit" aspectratio="t"/>
</v:shapetype><v:shape id="_x0000_i1027" type="#_x0000_t75" style='width:246pt;
height:89.25pt' o:ole="">
<v:imagedata src="./basic_files/image001.wmz" o:title=""/>
</v:shape><![endif]--><![if !vml]><img width=328 height=119
src="./basic_files/image002.gif" v:shapes="_x0000_i1027"><![endif]><!--[if gte mso 9]><xml>
<o:OLEObject Type="Embed" ProgID="Word.Picture.8" ShapeID="_x0000_i1027"
DrawAspect="Content" ObjectID="_1176123292">
</o:OLEObject>
</xml><![endif]--><o:p></o:p></span></p>
<h2><span lang=EN-US style='mso-ansi-language:EN-US'>Frequency consideration<o:p></o:p></span></h2>
<p class=MsoNormal><span lang=EN-US style='mso-ansi-language:EN-US'>The PWM DAC
resolution is equivalent to the resolution of the PWM signal you use to create
the DAC.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='mso-ansi-language:EN-US'>The PWM
output signal requires a frequency that is equivalent to the update rate of the
DAC, because each change in PWM duty cycle is the equivalent of one DAC sample.
<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='mso-ansi-language:EN-US'>The
required frequency of the PWM timer depends on the required PWM signal
frequency and the desired resolution. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='mso-ansi-language:EN-US'>The
required frequency is the PWM Clock<o:p></o:p></span></p>
<p align=center style='text-align:center'><span lang=EN-US style='mso-ansi-language:
EN-US'><!--[if gte vml 1]><v:shape id="_x0000_i1026" type="#_x0000_t75"
style='width:246pt;height:154.5pt' o:ole="">
<v:imagedata src="./basic_files/image003.wmz" o:title=""/>
</v:shape><![endif]--><![if !vml]><img width=328 height=206
src="./basic_files/image004.gif" v:shapes="_x0000_i1026"><![endif]><!--[if gte mso 9]><xml>
<o:OLEObject Type="Embed" ProgID="Word.Picture.8" ShapeID="_x0000_i1026"
DrawAspect="Content" ObjectID="_1176123293">
</o:OLEObject>
</xml><![endif]--><o:p></o:p></span></p>
<p><span lang=EN-US style='mso-ansi-language:EN-US'>Where PWM Clock FCLOCK is
the required PWM-timer frequency, Sampling frequency is the PWM sampling frequency,
and "n" is the desired DAC resolution<o:p></o:p></span></p>
<p><span lang=EN-US style='mso-ansi-language:EN-US'>The SAM7S64-IAR
implementation uses a MCK at 48 MHz and uses a 8-bit resolution and a range of
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -