xi

Foreword to The Hands-on XBee Lab Manual

The late 20th century saw the birth of connectivity. From simple computer net-works the Arpanet grew into the Internet. At first the playground of academics, nearly everyone is now connected to the “net” and therefore to everyone else and to vast amounts of data.

The 21st century has seen the dawn of the wireless era. Cell phones are no longer telecomm devices; they’re part of the vast Internet. Now we’re all connected all of the time, in the office or at the beach. Some of us use a smart phone more for data communications that voice transmissions. Indeed, that mobile device may have four or more antennas: one with a link to satellites in space for navigation, another to the 3G network, a wi-fi connection and Bluetooth for near-field links to headsets and the like.

Radio data communications surround us, from messages sent to the smart sign hanging over the highway to science instruments transmitting their find-ings from remote Arctic regions to a lab in some pastoral setting via a satellite uplink.

Why have a Bluetooth link from the phone to a headset? A wired approach is a nuisance. It’s bulky, in the way, and snags on things. Electronics is cheap; connectors are not, and the wireless version likely saves money and is more reliable. Messing with a tangle of cables in a lab or even with your PC is awk-ward. It won’t be long before those all go away.

It’s much more complicated to establish a link over an RF connection than with a wire, but smart hardware costs little today, and canned software is increasingly available. One popular option is Digi International’s line of XBee prepackaged radio modules. You don’t need to understand the nuances used, like direct-sequence spread spectrum coding or offset quadrature phase-shift keying, because those details are all taken care of by the modules.

You do need to understand how to use and interface to the modules, which is not made any easier by the terse and sometimes cryptic manuals. And XBee also uses the old AT command set, which is increasingly hard to find infor-mation about. For these reasons Jon Titus’s Hands on XBee Lab Manual is invaluable.

We learn in different ways. For many of us a hands-on approach is much more efficient than slogging through data books. Jon has taken that approach here, in a series of experiments designed teach by doing. From the very begin-ning you’ll be putting together components that make something neat happen. Early experiments emulate a single-direction wire: a receiver module’s output pin mirrors the input pin on the transmitter. Look Ma—no wires!

xii Foreword to The Hands-on XBee Lab Manual

Each lesson is progressively more complicated and useful. Send analog data through the ether. Control multiple XBee modules. Connect other embed-ded components, like an Arduino Uno or ARM mbed board to the XBee mod-ules. That, of course, is really the basis of embedded wireless networking.

Explore personal-area networks. These are self-assembling communica-tions links where the network discovers at run time which XBee modules are operating. Jon shows how to do this, and how to piece the network together. Along the way you’ll learn to handle interrupts, a crucial concept in the world of embedded systems.

Complex stuff. But fear not: Jon shows every step of each experiment. The lavish illustrations leave no chance for confusion. Whether it’s a screen shot of a communications tool or a drawing of how to connect a LED, nothing is left out.

Welcome to the second decade of the 21st century, the age of wireless data communications. This book is your essential guide to using XBee modules to toss off the shackles of wires.

Jack Ganssle