In this section, you will look in more detail at how to connect an XBee module. By the end of this section, you will better understand the connections described in the previous chapter, and will be able to figure out how to wire up other shields and adapters too.
Interfacing with an XBee module is not terribly complicated. All XBee modules offer a serial connection. In the most basic version, this involves just three pins on the XBee board: DIN (where the XBee module receives data), DOUT (where the XBee module sends data), and GND to establish a common ground reference.
This type of connection does not have any official name, but is commonly (but inaccurately) called TTL (Transistor-to-Transistor Logic) serial and is also used on the Arduino Uno between the integrated USB-to-serial converter and the main microcontroller.
It would be more accurate to say that it is an asynchronous, single-ended serial protocol running at 3.3V. Asynchronous indicates that there is...