All through this chapter, when we talk about serial communication, we will be referring to RS-232 standard protocol communication based on the Universal Asynchronous Receiver/Transmitter (UART) that the Arduino microcontroller incorporates. It is the most common communication type for most Arduino projects in comparison to other serial protocol communications that can also be established with Arduino and that we will briefly introduce in the next section.

The first thing we should know is why all these communication systems are called serial as opposed to parallel communications.

In the case of a serial communication, every bit of the data being transmitted is sent one piece at a time, through just a single line of the communication channel. In a parallel communication, data bits are sent in groups all at once, which makes it necessary to have a bigger number of communication lines in the channel.

This is perhaps the main reason to use serial communications in...