Interrupts allow the microcontroller to execute a function when an event occurs on one of the interrupt pins. Instead of constantly reading the value of a sensor, the program will only be triggered when the value of the sensor changes. This solves many task layout problems.
Material
- Arduino UNO
- push button (or other sensor)
- USB A/ USB B cable
Scheme
On the Arduino UNO board, there are two pins that support the interrupts: pins 2 and 3. So we will connect the output of the button to pin 2 of the Arduino.
Reminder of the digital pins compatible with the interrupts
| Uno, Nano, Mini, other 328-based | 2, 3 |
| Uno WiFi Rev.2, Nano Every | all digital pins |
| Mega, Mega2560, MegaADK | 2, 3, 18, 19, 20, 21 |
| Micro, Leonardo, other 32u4-based | 0, 1, 2, 3, 7 |
| Zero | all digital pins, except 4 |
| MKR Family boards | 0, 1, 4, 5, 6, 7, 8, 9, A1, A2 |
| Nano 33 IoT | 2, 3, 9, 10, 11, 13, 15, A5, A7 |
| Nano 33 BLE, Nano 33 BLE Sense | all pins |
| Due | all digital pins |
| 101 | all digital pins (Only pins 2, 5, 7, 8, 10, 11, 12, 13 work with CHANGE) |
Interrupt management code
The syntax to initialize an interrupt is as follows:
attachInterrupt(digitalPinToInterrupt(pin), ISR, mode)With pin, the pin used, ISR, the function to activate when the event is detected and mode, the detection mode used.
- LOW to enable detection when the spindle is in the LOW state
- CHANGE to activate the detection when the state of the spindle changes
- RISING to enable detection when the pin status changes from LOW to HIGH
- FALLING to enable detection when the pin status changes from HIGH to LOW
const byte ledPin = 13;
const byte interruptPin = 2;
volatile byte state = LOW;
void setup() {
Serial.begin(9600);
pinMode(ledPin, OUTPUT);
pinMode(interruptPin, INPUT_PULLUP);
attachInterrupt(digitalPinToInterrupt(interruptPin), onEvent, CHANGE);
Serial.println(F("Système intialisé"));
}
void loop() {
digitalWrite(ledPin, state);
}
void onEvent() {
state = !state;
Serial.print(F("Switch LED 13 : "));
if(state){
Serial.println(F("ON"));
}else{
Serial.println(F("OFF"));
}
}
Warning: In the onEvent() function, the millis() and delay() functions, which depend on interrupts, will not work.
Functions to know to go further in the management of interruptions
attachInterruptsdetachInterrupt(digitalPinToInterrupt(pin))disable the specified interruptinterrupts()re-enables interruptsnoInterrupts()to disable interrupts
Result
Once the code is uploaded, if you press the button, the LED on the Arduino should turn on and off.
Sources
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