From the mbed microcontroller Handbook.

InterruptIn

The InterruptIn interface is used to trigger an event when a digital input pin changes.

Any of the numbered mbed pins can be used as an InterruptIn, except p19 and p20.

Hello World!

Flip an LED every time we see the rising edge interrupt on a pin

#include "mbed.h"

InterruptIn button(p5);
DigitalOut led(LED1);
DigitalOut flash(LED4);

void flip() {
    led = !led;
}

int main() {
    button.rise(&flip);  // attach the address of the flip function to the rising edge
    while(1) {           // wait around, interrupts will interrupt this!
        flash = !flash;
        wait(0.25);
    }
}

API

API summary

InterruptIn	A digital interrupt input, used to call a function on a rising or falling edge
Functions
InterruptIn	Create an InterruptIn connected to the specified pin
rise	Attach a function to call when a rising edge occurs on the input
rise	Attach a member function to call when a rising edge occurs on the input
fall	Attach a function to call when a falling edge occurs on the input
fall	Attach a member function to call when a falling edge occurs on the input
mode	Set the input pin mode

class InterruptIn : public Base

A digital interrupt input, used to call a function on a rising or falling edge

InterruptIn( PinName pin,
const char * name = NULL )

Create an InterruptIn connected to the specified pin

void rise( void (*fptr)(void) )

Attach a function to call when a rising edge occurs on the input

void fall( void (*fptr)(void) )

Attach a function to call when a falling edge occurs on the input

void mode( PinMode pull )

Set the input pin mode

Details

The pin input will be logic '0' for any voltage on the pin below 0.8v, and '1' for any voltage above 2.0v. By default, the InterruptIn is setup with an internal pull-down resistor.

Examples

An example class for counting rising edges on a pin

#include "mbed.h"

class Counter {
public:
    Counter(PinName pin) : _interrupt(pin) {        // create the InterruptIn on the pin specified to Counter
        _interrupt.rise(this, &Counter::increment); // attach increment function of this counter instance
    }

    void increment() {
        _count++;
    }

    int read() {
        return _count;
    }

private:
    InterruptIn _interrupt;
    volatile int _count;
};

Counter counter(p5);

int main() {
    while(1) {
        printf("Count so far: %d\n", counter.read());
        wait(2);
    }
}

To read an input, see DigitalIn

For timer-based interrupts, see Ticker (repeating interrupt) and Timeout (one-time interrupt)

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Last modified 21 Jul 2010, by Dan Ros

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