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.. _lang-pulsein:
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
`HIGH <http://arduino.cc/en/Reference/Constants>`_ or
`LOW <http://arduino.cc/en/Reference/Constants>`_. (*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
-------
::
int pin = 7;
unsigned long duration;
void setup()
{
pinMode(pin, INPUT);
}
void loop()
{
duration = pulseIn(pin, HIGH);
}
.. include:: /lang/cc-attribution.txt
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