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<p class='vspace'></p><h2>pulseIn()</h2>
<h4>Description</h4>
<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 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. 
</p>
<p class='vspace'></p><h4>Syntax</h4>
<p>pulseIn(pin, value) <br />pulseIn(pin, value, timeout)
</p>
<p class='vspace'></p><h4>Parameters</h4>
<p>pin: the number of the pin on which you want to read the pulse.  (<em>int</em>)
</p>
<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>)
</p>
<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>)
</p>
<p class='vspace'></p><h4>Returns</h4>
<p>the length of the pulse (in microseconds) or 0 if no pulse started before the timeout (<em>unsigned long</em>)
</p>
<p class='vspace'></p><h4>Example</h4>
<pre> 

int pin = 7;
unsigned long duration;

void setup()
{
  pinMode(pin, INPUT);
}

void loop()
{
  duration = pulseIn(pin, HIGH);
}

</pre>
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