unity-android-serial-arduino

Connect an Arduino board to your Android device and send commands through the serial port from your Unity application/game.

Arduino

On the Arduino side, you need to create a small application that reads the serial port incoming commands and reacts accordingly. Take a look at this example for instance, that receives commands from the serial port and writes to a LCD 16x2 display: https://github.com/cvasquez-github/arduino-serial-to-i2c-lcd

Java

You need to write some Java code to communicate your Unity project with the Arduino board in Android through the USB serial port. In this example I created a custom Unity Activity to expose the necessary lower-level methods to Unity, take a look at the MyUnityPlayerActivity.java file for reference. https://github.com/cvasquez-github/unity-android-serial-arduino/blob/main/MyUnityPlayerActivity.java

Make sure you update the activity name in your Android Manifest XML file. https://github.com/cvasquez-github/unity-android-serial-arduino/blob/main/AndroidManifest.xml

This code uses the Android USB Serial Library (usb-serial-for-android-3.4.4.jar) to access the USB serial port: https://github.com/mik3y/usb-serial-for-android

Unity

Then you need to call the Java class methods from Unity. Take a look at the UnityArduinoLCD.cs file, that is the one that talks to the Java code. https://github.com/cvasquez-github/unity-android-serial-arduino/blob/main/UnityArduinoLCD.cs

• You first need to get the Unity Player Java Class: AndroidJavaClass unityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
• Then get the current activity Java Object out of it: AndroidJavaObject activity = unityPlayer.GetStatic<AndroidJavaObject>("currentActivity");
• Finally call the Java method on your current Activity: activity.Call("WriteLCD", new object[] { "line1", "line2" });

I used this on my Android-based 3D virtual pinball project to write the score of the game to a 16x2 LCD display, using an Arduino UNO board, from an nVidia Shield (Google TV).