There are three scenes that show how to read/write data from/to a serial device. There is a prefab that you need to add to your scene, this prefab will do all the thread management, queue ...

You can read the state of a button using Arduino and a few lines of code. The actual state is shown in the Serial Monitor window as 0 or 1, 0 meaning the button is not pressed and 1 that the button is ...