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
See Associated Table