Raspberry Pi can be used to interface with the real world from its GPIO, for example, by controlling a stepper motor. You can also use Raspberry Pi to dialog with some devices—like Arduino—by using a serial USB port. In this guide, I'll show you how to connect your Raspberry Pi to a serial USB port and read its values with Python from the terminal (without a desktop environment). For this purpose, we'll use Pyserial and its terminal tool.