Building Wireless Sensor Networks

Chapter 4. Ins and Outs

Congratulations—you now have configurations, communications, and some solid projects under your belt! It’s time to take a closer look at the unique features of the XBee brand of ZigBee radio so we can start building fully scalable sensor networks. We begin with input/output concepts and commands, then immediately put these to use in a small set of progressive projects that whimsically inculcate the basics.

The Story of Data

Before getting into the technical aspects of sensing data, it’s useful to take a step back and consider why it is we want to collect this type of information in the first place. After all, data has no value by itself. In its purest form, data is just a collection of numbers, and one set of numbers is as good as any other. Our real interest in data always comes from the story it might tell us. Gathering data is the first step in noticing new things in the world, proving a hunch, disproving a fallacy, or teaching a truth. It can also be a path to action. Patterns in data can trigger events, shape public policy, or just determine when it’s time to feed the cat. We should always have a purpose in mind when collecting data because that purpose will guide us in how the data is collected. This doesn’t mean we need to know what the data will tell us. Our purpose might be to simply gather results to examine for events or patterns that create new questions. This is known in science circles as exploratory data analysis—a well-accepted form of initial ...