iOS Sensor Apps with Arduino

Chapter 5. Connecting to an XBee Network

All of the incarnations of the iPhone, iPod touch, and iPad come with WiFi networking, or more formally, IEEE 802.11. This is a set of standards for implementing wireless local area networking (WLAN) computer communication in the 2.4, 3.6, and 5 GHz frequency bands, although none of the existing iOS-based devices support anything other than the 2.4 GHz band.

However, there are many other standards for wireless communication, many of which also make use of the 2.4 GHz band, which are intended for other purposes and hence designed in a different fashion. They may use the same wavelength bands, but the protocols are very different.

One of the most commonly used protocols when dealing with sensor networks is IEEE 802.15.4. In contrast to IEEE 802.11, this protocol focuses on low-cost, low-speed communication between devices and is intended for low-power scenarios. It is the basis for the higher-level ZigBee protocol, also commonly found when dealing with sensor networks, which further extends the standard by developing the upper layer protocols to enable mesh networking between devices.

While many other bands of 802.15.4-based hardware exist, probably the most heavily used are the XBee branded radios. They’re in common use, both by professionals who use them for prototyping, and in the hobbyist market, because they’re especially easy for beginners to use. For this and other reasons I’m going to focus on the XBee-branded radio modules that are manufactured ...