======pulseIn()   ======

====Description   ====
Reads a pulse (either HIGH or LOW) on a pin.  For example, if **value** is **HIGH**, **pulseIn()** waits for the pin to go **HIGH**, starts timing, then waits for the pin to go **LOW** 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.

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. 

====Syntax   ====
pulseIn(pin, value) \\
pulseIn(pin, value, timeout)


====Parameters   ====
pin: the number of the pin on which you want to read the pulse.  (''int'')

value: type of pulse to read: either [[arduino:variable scope and qualifiers:Constants|HIGH]] or [[arduino:variable scope and qualifiers:Constants|LOW]]. (''int'')

timeout (optional): the number of microseconds to wait for the pulse to start; default is one second (''unsigned long'')

====Returns   ====
the length of the pulse (in microseconds) or 0 if no pulse started before the timeout (''unsigned long'')

====Example   ====
 <code arduino>

int pin = 7;
unsigned long duration;

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

void loop()
{
  duration = pulseIn(pin, HIGH);
}
</code>


Source: arduino.cc