Each XBee radio has a tiny computer on board. This internal microcontroller runs a program, also known as firmware, that performs all its addressing, communication, security, and utility functions. You can configure this firmware with different settings that define things like its local address, which type of security is enforced, who it should send messages to, and how it should read sensors connected to its local input pins.

To change or upgrade the firmware, we will use a program called X-CTU that you can download from the Digi website. On the upside, this program is totally free. On the downside, it runs only on Windows. Don’t worry if you have limited access to Windows, though. Chances are you’ll only need X-CTU initially, to load the proper firmware onto your XBee radio. Going forward, you can use serial terminal programs on Macintosh, Linux, or Windows to change many of the settings you’ll be working with on a day-to-day basis. Let’s take a look at some of these programs and how they operate.