Arduino Tutorial

By LiterallyTheOne

6: Interrupt

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Introduction

Previous tutorial: Analog
This tutorial: Interrupt

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External Interrupt

Special Signal
Pause the current action
Run a code in a function
Interrupt Service Routine Function (ISR Function)

External Interrupt in Arduino Uno

2 External Interrupts
pin 2, 3

Setup LEDs

setup leds height:450

Write a Routine

#include <Arduino.h>

int led_pins[8] = {6, 7, 8, 9, 10, 11, 12, 13};

int current_led = 0;

void setup()
{
  for (int i = 0; i < 8; i++)
  {
    pinMode(led_pins[i], OUTPUT);
  }
}

void loop()
{
  digitalWrite(led_pins[current_led], HIGH);
  delay(200);
  digitalWrite(led_pins[current_led], LOW);

  current_led++;
  current_led %= 8;
}

Output of LED setup

LED stup gif height:450

Connect an Interrupt

Button is Normally Closed
Default: 5V
Change: 0V

LED pause bg right:50% height:410

Define Interrupt in Arduino

attachInterrupt
- pin
- ISR function
- mode

Define Interrupt pin

digitalPinToInterrupt

attachInterrupt(digitalPinToInterrupt(2), ... ,...);

Define ISR function

void isr_pause()
{
}

attachInterrupt(digitalPinToInterrupt(2), isr_pause ,...);

Modes

Mode	Description	figure
LOW	trigger the interrupt whenever the pin is low.
CHANGE	trigger the interrupt whenever the pin changes value.
RISING	trigger when the pin goes from low to high.
FALLING	trigger when the pin goes from high to low.

Add mode

attachInterrupt(digitalPinToInterrupt(2), isr_pause, RISING);

Fill the isr function

#include <Arduino.h>

int led_pins[8] = {6, 7, 8, 9, 10, 11, 12, 13};

int current_led = 0;
int x = 1;

void isr_pause()
{
  x = 1 - x;
}

void setup()
{
  for (int i = 0; i < 8; i++)
  {
    pinMode(led_pins[i], OUTPUT);
  }

  attachInterrupt(digitalPinToInterrupt(2), isr_pause, RISING);
}

void loop()
{
  digitalWrite(led_pins[current_led], HIGH);
  delay(200);
  digitalWrite(led_pins[current_led], LOW);

  current_led += x;
  current_led %= 8;
}

Output of pause interrupt

pause interrupt h:450

Volatile in Cpp

Stops Compiler optimazation for a variable

volatile int v;

Reset with Interrupt

Interrupt reset height:450

Increment pattern

Incerement pattern height:450

LEDS dance

LEDs dance height:450

Link to the tutorial and materials

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