Wake-up from sleep with interrupt in Arduino - Mini Project: Build & Apply

Wake-up from Sleep with Interrupt

📖 Scenario: You are building a simple Arduino project that saves power by going to sleep and wakes up only when a button is pressed. This is useful for battery-powered devices that need to stay off most of the time and react only to user input.

🎯 Goal: Create an Arduino program that puts the board to sleep and wakes it up using an external interrupt triggered by a button press.

📋 What You'll Learn

Use the LowPower library to manage sleep mode

Set up a button connected to pin 2 to trigger an interrupt

Use an interrupt service routine (ISR) to wake the Arduino

Print a message to the Serial Monitor when the Arduino wakes up

💡 Why This Matters

🌍 Real World

Battery-powered devices like remote sensors or wearable gadgets often need to save power by sleeping and waking only when needed.

💼 Career

Understanding interrupts and power management is essential for embedded systems engineers and IoT developers to build efficient, low-power devices.

1

Setup button input and Serial communication

Write code to set up the button on pin 2 as an input with an internal pull-up resistor. Also, start the Serial communication at 9600 baud in the setup() function.

Arduino

void setup() {
  // Set pin 2 as input with internal pull-up resistor
  // Start Serial communication at 9600 baud
  // Your code here
}

void loop() {
  // Empty loop for now
}

Need a hint?

Use pinMode to set the button pin as input with pull-up. Use Serial.begin(9600) to start serial communication.

2

Configure interrupt to wake from sleep

Add code to attach an interrupt on pin 2 that triggers on a falling edge. Create an empty interrupt service routine called wakeUp that will be called when the interrupt occurs.

Arduino

void setup() {
  pinMode(2, INPUT_PULLUP);
  Serial.begin(9600);
  // Attach interrupt on pin 2 for falling edge to wakeUp
  // Your code here
}

void loop() {
  // Empty loop for now
}

// Define the wakeUp ISR
void wakeUp() {
  // Your code here
}

Need a hint?

Use attachInterrupt(digitalPinToInterrupt(2), wakeUp, FALLING) to set the interrupt. The ISR wakeUp should be empty or very short.

3

Put Arduino to sleep and wake on interrupt

Include the LowPower.h library at the top. In the loop() function, put the Arduino to sleep using LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF). The Arduino will wake up when the interrupt triggers.

Arduino

#include 

void setup() {
  pinMode(2, INPUT_PULLUP);
  Serial.begin(9600);
  attachInterrupt(digitalPinToInterrupt(2), wakeUp, FALLING);
}

void loop() {
  // Put Arduino to sleep here
  // Your code here
}

void wakeUp() {
  // ISR must be empty or minimal
}

Need a hint?

Include the LowPower library and call LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF) inside loop() to sleep indefinitely until interrupt.

4

Print message after waking up

Add a Serial.println("Woke up!") statement right after the sleep call in the loop() function to show when the Arduino wakes up.

Arduino

#include 

void setup() {
  pinMode(2, INPUT_PULLUP);
  Serial.begin(9600);
  attachInterrupt(digitalPinToInterrupt(2), wakeUp, FALLING);
}

void loop() {
  LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
  // Print "Woke up!" after waking up
  // Your code here
}

void wakeUp() {
  // ISR must be empty or minimal
}

Need a hint?

Use Serial.println("Woke up!") after the sleep call to show the wake-up message.