ZigBee and 802.15.4 are hot these days, even though the bandwidth tops out at 250 kbits/s. Chips are available from a variety of sources. Yet many developers will use modules to simplify designs and eliminate the Federal Communications Commission approval process.
I've been reviewing many of these ZigBee/802.15.4 kits, including those based on modules (see "ZigBee Kits" at www.electronicdesign.com, ED Online 11570, and "ZigBee Kits 2" at ED Online 16483). Overall, they're easy to use. Additionally, they include most of the tools necessary to develop applications. But they tend to be more sophisticated than the typical micorcontroller development kit.
For example, it's usually a good idea to look for a monitoring system. Some kits include USB-based adapters that enable a PC to become part of a wireless network. Others use one of the systems to provide this functionality.
STACKS AND CHIPS Most chip-based solutions come on modules, but generally, they aren't designed for resale or incorporation into designs (Fig. 1). They're typically available from the chip vendor. These platforms usually provide the 802.15.4 or ZigBee protocol stacks in source form as part of the package since they become part of the delivered application.
Developers taking this approach need to be aware of FCC approval, making it less desirable for small production runs. Likewise, the use of ZigBee may entail additional licensing issues.
WIRELESS MODULES The usual alternative is to design in modules that already have approvals like MaxStream's module (Fig. 2). This can reduce time-to-market and take advantage of the wireless design expertise of the supplier, which can be a significant benefit for designers who want to concentrate on their aspect of the product design. The modules often have a simple serial interface that makes connection to a host microcontroller almost trivial since the complexities of the protocol stacks are hidden.
Developers can evaluate designs with most kits in an afternoon, but application development will typically take much longer.
Ember • www.ember.com
Oki America • www.okisemi.com
MaxStream • www.maxstream.net
ZigBee Alliance • www.zigbee.org
