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117 lines
4.8 KiB
HTML
117 lines
4.8 KiB
HTML
15 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html>
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<head>
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<title>Arduino - Random </title>
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<link rel='stylesheet' href='arduino.css' type='text/css' />
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<meta name="verify-v1" content="TtxFIEJAB6zdJ509wLxjnapQzKAMNm9u0Wj4ho6wxIY=" />
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</head>
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<body>
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<div id="page">
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<!--PageHeaderFmt-->
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<div id="pageheader">
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<div class="title"><a href="http://www.arduino.cc"/>Arduino</a></div>
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<div class="search">
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<FORM method=GET action="http://www.google.com/search">
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<INPUT TYPE=text name=q size=25 maxlength=255 value="">
<INPUT type=submit name=btnG VALUE="search">
<input type=hidden name=domains value="http://www.arduino.cc/">
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<input type=hidden name=sitesearch value="http://www.arduino.cc/">
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</FORM>
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</div>
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</div>
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<div id="pagenav" style="text-align: right">
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<div style="float: left;">
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<p><a class='wikilink' href='http://arduino.cc/en/Main/Buy'>Buy</a>
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<a class='wikilink' href='http://arduino.cc/en/Main/Software'>Download</a>
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<a class='wikilink' href='Guide_index.html'>Getting Started</a>
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<a class='wikilink' href='http://arduino.cc/en/Tutorial/HomePage'>Learning</a>
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<a class='wikilink' href='index.html'>Reference</a>
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<a class='wikilink' href='http://arduino.cc/en/Main/Hardware'>Hardware</a>
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<a class='wikilink' href='FAQ.html'>FAQ</a>
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</p>
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<p class='vspace'></p>
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</div>
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<a class="urllink" href="http://www.arduino.cc/blog/" rel="nofollow">Blog »</a> |
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<a class="urllink" href="http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl" rel="nofollow">Forum »</a> |
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<a class="urllink" href="http://www.arduino.cc/playground/" rel="nofollow">Playground »</a>
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<div id="pagetext">
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<div id='wikitext'>
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<p><strong>Reference</strong> <a class='wikilink' href='index.html'>Language</a> (<a class='wikilink' href='Extended.html'>extended</a>) | <a class='wikilink' href='Libraries.html'>Libraries</a> | <a class='wikilink' href='Comparison.html'>Comparison</a> | <a class='wikilink' href='Changes.html'>Changes</a>
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</p>
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<p class='vspace'></p><h2>random()</h2>
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<h4>Description</h4>
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<p>The random function generates pseudo-random numbers.
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</p>
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<p class='vspace'></p><h4>Syntax</h4>
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<p>random(max)<br />random(min, max)
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</p>
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<p class='vspace'></p><h4>Parameters</h4>
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<p>min - lower bound of the random value, inclusive <em>(optional)</em>
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</p>
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<p class='vspace'></p><p>max - upper bound of the random value, exclusive
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</p>
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<p class='vspace'></p><h4>Returns</h4>
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<p>a random number between min and max-1 (<em>long</em>)
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</p>
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<p class='vspace'></p><h4>Note: </h4>
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<p>If it is important for a sequence of values generated by random() to differ, on subsequent executions of a sketch, use randomSeed() to initialize the random number generator with a fairly random input, such as analogRead() on an unconnected pin.
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</p>
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<p class='vspace'></p><p>Conversely, it can occasionally be useful to use pseudo-random sequences that repeat exactly. This can be accomplished by calling randomSeed() with a fixed number, before starting the random sequence.
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</p>
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<p class='vspace'></p><h4>Example</h4>
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<pre>
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long randNumber;
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void setup(){
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Serial.begin(9600);
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// if analog input pin 0 is unconnected, random analog
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// noise will cause the call to randomSeed() to generate
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// different seed numbers each time the sketch runs.
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// randomSeed() will then shuffle the random function.
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randomSeed(analogRead(0));
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}
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void loop() {
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// print a random number from 0 to 299
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randNumber = random(300);
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Serial.println(randNumber);
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// print a random number from 10 to 19
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randNumber = random(10, 20);
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Serial.println(randNumber);
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delay(50);
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}
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</pre>
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<p class='vspace'></p><h4>See also</h4>
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<ul><li><a class='wikilink' href='RandomSeed.html'>randomSeed</a>()
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</li></ul><p class='vspace'></p><p><a class='wikilink' href='index.html'>Reference Home</a>
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</p>
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<p class='vspace'></p><p><em>Corrections, suggestions, and new documentation should be posted to the <a class='urllink' href='http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?board=swbugs' rel='nofollow'>Forum</a>.</em>
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</p>
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<p class='vspace'></p><p>The text of the Arduino reference is licensed under a
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<a class='urllink' href='http://creativecommons.org/licenses/by-sa/3.0/' rel='nofollow'>Creative Commons Attribution-ShareAlike 3.0 License</a>. Code samples in the reference are released into the public domain.
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</p>
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</div>
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</div>
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<div id="pagefooter">
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<a href='#'>Edit Page</a> | <a href='#'>Page History</a> | <a href='#' target='_blank'>Printable View</a> | <a href='http://arduino.cc/en/Site/AllRecentChanges'>All Recent Site Changes</a>
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</html>
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