Input/Output - Advanced


Since 0.4.7:

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 or 0 if no complete pulse was received within the timeout.

The timing of this function is based on an internal hardware counter derived from the system tick clock. Resolution is 1/120MHz for Photon/P1/Electron). Works on pulses from 10 microseconds to 3 seconds in length. Please note that if the pin is already reading the desired value when the function is called, it will wait for the pin to be the opposite state of the desired value, and then finally measure the duration of the desired value. This routine is blocking and does not use interrupts. The pulseIn() routine will time out and return 0 after 3 seconds.

pulseIn(pin, value)

pulseIn() takes two arguments, pin: the pin on which you want to read the pulse (this can be any GPIO, e.g. D1, A2, C0, B3, etc..), value: type of pulse to read: either HIGH or LOW. pin should be set to one of three pinMode()'s prior to using pulseIn(), INPUT, INPUT_PULLUP or INPUT_PULLDOWN.

pulseIn() returns the length of the pulse (in microseconds) or 0 if no pulse is completed before the 3 second timeout (unsigned long)

SerialLogHandler logHandler;

unsigned long duration;

void setup()
    pinMode(D0, INPUT);

    // Pulse generator, connect D1 to D0 with a jumper
    // PWM output is 500Hz at 50% duty cycle
    // 1000us HIGH, 1000us LOW
    pinMode(D1, OUTPUT);
    analogWrite(D1, 128);

void loop()
    duration = pulseIn(D0, HIGH);"%d us", duration);

 * 1003 us
 * 1003 us
 * 1003 us
 * 1003 us