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104 lines
4.7 KiB
HTML
104 lines
4.7 KiB
HTML
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<title>Arduino - PulseIn </title>
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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 class='vspace'></p><h2>pulseIn()</h2>
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<h4>Description</h4>
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<p>Reads a pulse (either HIGH or LOW) on a pin. For example, if <strong>value</strong> is <strong>HIGH</strong>, <strong>pulseIn()</strong> waits for the pin to go <strong>HIGH</strong>, starts timing, then waits for the pin to go <strong>LOW</strong> and stops timing. Returns the length of the pulse in microseconds. Gives up and returns 0 if no pulse starts within a specified time out.
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</p>
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<p class='vspace'></p><p>The timing of this function has been determined empirically and will probably show errors in longer pulses. Works on pulses from 10 microseconds to 3 minutes in length.
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</p>
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<p class='vspace'></p><h4>Syntax</h4>
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<p>pulseIn(pin, value) <br />pulseIn(pin, value, timeout)
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</p>
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<p class='vspace'></p><h4>Parameters</h4>
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<p>pin: the number of the pin on which you want to read the pulse. (<em>int</em>)
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</p>
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<p class='vspace'></p><p>value: type of pulse to read: either <a class='wikilink' href='Constants.html'>HIGH</a> or <a class='wikilink' href='Constants.html'>LOW</a>. (<em>int</em>)
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</p>
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<p class='vspace'></p><p>timeout (optional): the number of microseconds to wait for the pulse to start; default is one second (<em>unsigned long</em>)
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</p>
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<p class='vspace'></p><h4>Returns</h4>
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<p>the length of the pulse (in microseconds) or 0 if no pulse started before the timeout (<em>unsigned long</em>)
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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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int pin = 7;
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unsigned long duration;
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void setup()
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{
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pinMode(pin, INPUT);
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}
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void loop()
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{
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duration = pulseIn(pin, HIGH);
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}
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</pre>
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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 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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