Tips for designing ZigBee applications

The tips presented here can’t answer all of these questions for everybody but they will provide a tutorial for the development of your ZigBee application.

The first and perhaps most important step in developing your application is to determine whether ZigBee is appropriate for your product. The ZigBee radio standard boasts many advantages over other wireless options.

With a public ZigBee profile and conformant platform, interoperability with other vendor devices is assured. ZigBee was defined to support extremely low power and remarkably long battery life. But the ZigBee data rates are low relative to other wireless options. And while substantially smaller than Bluetooth or 802.11/WiFi, the ZigBee stack is not a simple piece of software.

Partnering
After deciding that you want to develop a ZigBee application, you must choose a ZigBee provider partner. A ZigBee partner will supply the ZigBee stack software along with a radio chip and baseband microcontroller.

Historically, these have been two chip solutions. Recently, though, vendors have been introducing single chip ZigBee devices with plenty of additional resources to support your application code. A quality ZigBee partner will also supply you with continual updates on the most recent features.

Several ZigBee providers are available, and each has invested many person-years of development to arrive at their ZigBee solution. In choosing a partner, you should consider technical aspects (the cost vs. capability of their chipset, supported features) and business aspects of the provider (company history, licensing costs, technical support).

The ZigBee providers will also want to know about you—information such as your previous product development experience and the number of devices that you plan to sell. When this exchange of information is complete, you should rather quickly be able to find a ZigBee provider willing to collaborate on your application.

After you have chosen a ZigBee provider, you must then decide how to implement the ZigBee radio—as a module connected to the rest of the system or as a chip integrated into the circuitry of your board.

Using a ZigBee radio module offers many advantages. A module usually leads to a shorter development cycle. The RF design is already done for you—so you don’t need to become an RF expert. In addition, a module may carry FCC Modular Approval, which means you won’t have to take your product through the FCC’s intentional radiator approval process.

Disadvantages to using a ZigBee radio module versus an integrated ZigBee chip include a higher per-unit product cost. A module design also requires more physical space inside the housing and imposes more constraints on the industrial design of the product. What’s more, a module may have limited antenna options, which may be unsuitable for your product.

The final architecture task is to completely define your ZigBee network structure. The ZigBee standard supports multiple topologies for you to choose from. These include mesh, star, and cluster tree network configurations, which are shown in Figure 1.

Click here for Figure 1
Figure 1: Network structure diagram showing mesh, star and cluster tree network configuration options.

The typical ZigBee network configuration is comprised of low power reduced function end point devices, generally called sensors. The sensors communicate with full function network control devices that handle the routing of packets over the network.