Timer interrupts with TimerOne library in Arduino - Mini Project: Build & Apply

Timer interrupts with TimerOne library

📖 Scenario: You want to blink an LED on your Arduino board at a steady pace without using the delay() function. Using timer interrupts helps you do this efficiently.

🎯 Goal: Build a program that uses the TimerOne library to blink the built-in LED every 1 second using timer interrupts.

📋 What You'll Learn

Use the TimerOne library to set up a timer interrupt

Create an interrupt service routine (ISR) to toggle the LED

Set the timer to trigger every 1 second (1000000 microseconds)

Use the built-in LED on pin 13

💡 Why This Matters

🌍 Real World

Timer interrupts are used in real devices to perform tasks regularly without stopping other work, like blinking status lights or reading sensors.

💼 Career

Understanding timer interrupts is important for embedded systems programming, robotics, and hardware control jobs.

1

Set up the LED pin

Create a variable called ledPin and set it to 13. Then, in the setup() function, set ledPin as an output using pinMode(ledPin, OUTPUT);.

Arduino

int ledPin = 13;

void setup() {
  pinMode(ledPin, OUTPUT);
  // Your code here
}

void loop() {
  // Empty loop
}

Need a hint?

Use int ledPin = 13; and pinMode(ledPin, OUTPUT); inside setup().

2

Include TimerOne library and declare a volatile variable

Add #include <TimerOne.h> at the top. Then, create a volatile bool ledState variable and set it to false to track the LED state.

Arduino

#include 

int ledPin = 13;
volatile bool ledState = false;

void setup() {
  pinMode(ledPin, OUTPUT);
  // Your code here
}

void loop() {
  // Empty loop
}

Need a hint?

Include the TimerOne library and declare volatile bool ledState = false; before setup().

3

Set up TimerOne to call the interrupt function every 1 second

In the setup() function, add Timer1.initialize(1000000); to set the timer for 1 second intervals. Then add Timer1.attachInterrupt(toggleLED); to call the toggleLED function on each interrupt. Also, write the toggleLED() function that toggles ledState and sets the LED pin accordingly.

Arduino

#include 

int ledPin = 13;
volatile bool ledState = false;

void setup() {
  pinMode(ledPin, OUTPUT);
  Timer1.initialize(1000000); // 1 second
  Timer1.attachInterrupt(toggleLED);
  // Your code here
}

void loop() {
  // Empty loop
}

void toggleLED() {
  ledState = !ledState;
  digitalWrite(ledPin, ledState);
}

Need a hint?

Use Timer1.initialize(1000000); and Timer1.attachInterrupt(toggleLED); in setup(). Define toggleLED() to flip ledState and write it to ledPin.

4

Print a message to confirm the program is running

In the setup() function, add Serial.begin(9600); to start serial communication. Then add Serial.println("Timer interrupt started"); to print a confirmation message.

Arduino

#include 

int ledPin = 13;
volatile bool ledState = false;

void setup() {
  pinMode(ledPin, OUTPUT);
  Timer1.initialize(1000000); // 1 second
  Timer1.attachInterrupt(toggleLED);
  Serial.begin(9600);
  // Your code here
}

void loop() {
  // Empty loop
}

void toggleLED() {
  ledState = !ledState;
  digitalWrite(ledPin, ledState);
}

Need a hint?

Use Serial.begin(9600); and Serial.println("Timer interrupt started"); in setup().