Tuesday, November 11, 2014

How to Interrupt Your Arduino

In this video tutorial we will look at how to use interupts on the Arduino Uno, Arduino Pro Mini, and any Arduino using the Atmega 328. Interrupts allow you to react immediately to an external event versus trying to constantly check for it in the main loop. 

Arduino Code****************************************************************
  Interrupt Example
  Demonstrates how to use interrupts. When a high level is detected at pin 2 interrupt occurs and blinks LED at pin 13

  This example code is in the public domain.

// Pin 13 has an LED connected on most Arduino boards.
// give it a name:
int led = 13;
//create a variable for ISR, has to be volatile if used in interrupt
volatile int bLED = 0;

void setup() {
  //Create interrupt: 0 for pin 2 or 1 for pin 3, the name of the interrupt function or ISR, and condition to trigger interrupt 
  attachInterrupt(0, interruptFunction, HIGH); 
  pinMode(led, OUTPUT); //set up the LED pin to output

// the loop routine runs over and over again forever:
void loop() {
  if(bLED) { //if this statement becomes true then the interrupt occurred
    digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(300);               // wait 
    digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
    delay(300);               // wait 
  noInterrupts(); //disables interrupts
  // critical, time-sensitive code here
  interrupts();//enables interrupts

//This is the function called when the interrupt occurs (pin 2 goes high)
//this is often referred to as the interrupt service routine or ISR
//This cannot take any input arguments or return anything
void interruptFunction() {
 bLED = 1; //with this variable set to 1 the LED will blink
 //detachInterrupt(0); this function call will turn the interrupt off