Building Wireless Sensor Networks

Chapter 2. Up and Running

Here is the heart of the book. We go from a bag of parts to a working ZigBee network in one chapter, taking the simplest path to early success. Addresses, firmware, and configuration steps culminate in a simple chat session for a satisfying exchange of greetings. Hello world, you are up and running.

Let’s get started.

Radio Basics

What exactly is this thing called radio? In any dictionary or encyclopedia, you’ll find a definition that describes the transmission of information via modulation of waves in the electromagnetic spectrum. Whoa, that’s pretty mysterious, especially when coupled with the mathematics and equations that describe the behavior of radio. These certainly help us work with the medium, yet they still may not answer the question of what it is. If you feel unsatisfied by the words or the math, that’s OK. One helpful way to think of radio is as a well-described mystery. After all, we can’t see radio. We can’t touch radio or hear it or smell it or feel it. Billions of years of evolution haven’t provided us with any direct sensory apparatus for perceiving the radio part of the electromagnetic spectrum at all. Our language around the phenomenon reveals this. The word radio comes from radius, the Latin for a ray or spoke in a wheel, something that propagates from a center outward. True, but pretty vague. Around the turn of the last century it was referred to as “ethereal communication” in a nod to the “ether” that was incorrectly thought to pervade ...