Non-blocking code architecture in Arduino - Mini Project: Build & Apply

Non-blocking Code Architecture in Arduino

📖 Scenario: You are building a simple Arduino program to blink an LED without stopping other tasks. Instead of using delay(), which pauses everything, you will learn how to write non-blocking code that lets the Arduino do other things while blinking the LED.

🎯 Goal: Create an Arduino sketch that blinks the built-in LED every 1 second using non-blocking code with millis(). This will keep the program responsive and able to do other tasks.

📋 What You'll Learn

Use the built-in LED on pin 13

Use a variable to store the LED blink interval (1000 milliseconds)

Use millis() to check elapsed time without blocking

Toggle the LED state every interval

Print LED ON or LED OFF to the Serial Monitor when the LED changes

💡 Why This Matters

🌍 Real World

Non-blocking code lets microcontrollers handle multiple tasks smoothly, like reading sensors while blinking LEDs or controlling motors without delays.

💼 Career

Understanding non-blocking code is essential for embedded systems programming, robotics, and IoT device development where responsiveness is critical.

1

Setup LED pin and initial variables

Create a variable called ledPin and set it to 13. Create a variable called previousMillis and set it to 0. Create a variable called ledState and set it to LOW. In the setup() function, set ledPin as an output and start Serial communication at 9600 baud.

Arduino

int ledPin = 13;
unsigned long previousMillis = 0;
int ledState = LOW;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
  // Your code here
}

void loop() {
  // Your code here
}

Need a hint?

Remember to set the LED pin as output and start Serial communication in setup().

2

Add blink interval variable

Add a variable called interval and set it to 1000 to represent the blink interval in milliseconds.

Arduino

int ledPin = 13;
unsigned long previousMillis = 0;
int ledState = LOW;
unsigned long interval = 1000;  // Your code here

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Your code here
}

Need a hint?

Use unsigned long for the interval variable to match millis() type.

3

Implement non-blocking LED blink logic

In the loop() function, get the current time using millis() and store it in a variable called currentMillis. Use an if statement to check if the difference between currentMillis and previousMillis is greater than or equal to interval. Inside the if, update previousMillis to currentMillis, toggle ledState between LOW and HIGH, write ledState to ledPin, and print LED ON or LED OFF to Serial depending on the new state.

Arduino

int ledPin = 13;
unsigned long previousMillis = 0;
int ledState = LOW;
unsigned long interval = 1000;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  unsigned long currentMillis = millis();
  // Your code here
}

Need a hint?

Use millis() to check elapsed time and toggle the LED state inside the if block.

4

Display blinking LED status

Add a print statement inside the if block in loop() to print LED ON when the LED turns on and LED OFF when it turns off. This is already done in the previous step. Run the program and observe the Serial Monitor output showing LED ON and LED OFF every second.

Arduino

int ledPin = 13;
unsigned long previousMillis = 0;
int ledState = LOW;
unsigned long interval = 1000;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    if (ledState == LOW) {
      ledState = HIGH;
      Serial.println("LED ON");
    } else {
      ledState = LOW;
      Serial.println("LED OFF");
    }
    digitalWrite(ledPin, ledState);
  }
  // Your code here
}

Need a hint?

Open the Serial Monitor to see the LED status messages every second.