First Project: Blink an LED from Java

In this tutorial, you will build a complete Java application that controls the built-in LED on an Arduino board. This covers the full workflow: project setup, firmware upload, Java code, and running it.

What You Need

  • Arduino Uno (or compatible board)
  • USB cable
  • Java 11+ with Maven
  • A text editor or IDE

1. Create the Maven Project 

mkdir ardulink-blink && cd ardulink-blink

Create pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
                             http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>ardulink-blink</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.ardulink</groupId>
            <artifactId>ardulink-core-base</artifactId>
            <version>2.3.1</version>
        </dependency>
        <dependency>
            <groupId>org.ardulink</groupId>
            <artifactId>ardulink-link-serial-jssc</artifactId>
            <version>2.3.1</version>
        </dependency>
    </dependencies>
</project>

2. Flash the Firmware

Open the WebSerial Flasher in your browser, connect your Arduino, and click Program. This uploads the Ardulink protocol firmware that lets Java communicate with the board.

See Arduino Firmware Setup for more details.

3. Write the Java Code

Create src/main/java/com/example/Blink.java:

package com.example;

import java.util.concurrent.TimeUnit;

import org.ardulink.core.Link;
import org.ardulink.core.pin.Pin;
import org.ardulink.core.pin.Pin.DigitalPin;
import org.ardulink.core.convenience.Links;

public class Blink {

    public static void main(String... args) throws Exception {
        try (Link link = Links.getDefault()) {
            DigitalPin pin = Pin.digitalPin(13);
            boolean state = true;

            System.out.println("Starting LED blink. Press Ctrl+C to stop.");

            while (true) {
                link.switchDigitalPin(pin, state);
                System.out.printf("LED %s%n", state ? "ON" : "OFF");
                TimeUnit.SECONDS.sleep(1);
                state = !state;
            }
        }
    }
}

What This Code Does

  1. Links.getDefault() — Creates a connection using the first available link adapter on the classpath. With ardulink-link-serial-jssc present, it connects to the Arduino over serial.

  2. Pin.digitalPin(13) — References digital pin 13, which is connected to the built-in LED on most Arduino boards.

  3. link.switchDigitalPin(pin, state) — Sends a command to the Arduino to set pin 13 HIGH (true) or LOW (false).

  4. The try-with-resources block ensures the connection is closed when the program exits (Ctrl+C).

4. Run It 

mvn compile exec:java -Dexec.mainClass="com.example.Blink"

You should see:

Starting LED blink. Press Ctrl+C to stop.
LED ON
LED OFF
LED ON
LED OFF
...

And the built-in LED on your Arduino should blink once per second.

5. Reading Pin Values

Now let’s extend this to also read a button connected to pin 2:

package com.example;

import java.util.concurrent.TimeUnit;

import org.ardulink.core.Link;
import org.ardulink.core.pin.Pin;
import org.ardulink.core.pin.Pin.DigitalPin;
import org.ardulink.core.events.PinChangedEvent;
import org.ardulink.core.events.FilteredEventListenerAdapter;
import org.ardulink.core.convenience.Links;

public class BlinkWithButton {

    public static void main(String... args) throws Exception {
        try (Link link = Links.getDefault()) {
            DigitalPin ledPin = Pin.digitalPin(13);
            DigitalPin buttonPin = Pin.digitalPin(2);

            // Listen for button presses on pin 2, filtered automatically
            link.addListener(FilteredEventListenerAdapter.filter(
                PinChangedEvent.class,
                buttonPin,
                pinEvent -> System.out.printf("Button pressed: %s%n", pinEvent.getValue())
            ));

            // Start listening on pin 2
            link.startListening(buttonPin);
            System.out.println("Listening on pin 2. Press the button...");

            // Blink LED while waiting
            boolean state = true;
            while (true) {
                link.switchDigitalPin(ledPin, state);
                TimeUnit.SECONDS.sleep(1);
                state = !state;
            }
        }
    }
}

Next Steps