Functionality: Android talks to Arduino
1. Run the Android "Bluetooth Chat" sample app (after we modify the app in this instructable). Type a message in the app's text box and press the "send" button. The message you typed echoes on the app display.
2. Message travels through the air from the built-in Android Bluetooth modem to the Bluetooth modem connected to the Arduino Uno.
3. Arduino Uno receives the typed message.
4. The Arduino Uno prints the typed message on the LCD.
Functionality: Arduino talks to Android
1. Every 30 seconds, the Arduino sends a message ("hello from Arduino") to the Android phone via Bluetooth.
2. The Arduino message appears on the Android "Bluetooth Chat" sample app display.
Why? Just an easy way to test the Arduino's ability to not only receive messages from, but send messages to the Android phone. You can take the example sketch and change it however you want.
Here's the full video instruction that we'll break out into steps: