March 2005, Issue 176

Zeroing in on ZigBee (Part 2)
Chipsets and Source Code

NOW’S THE TIME

Until now, it has been difficult to make a real ZigBee node on a tight budget. Although ZigBee-compatible hardware has been readily available for more than six months, the software stack above the 802.15.4 layers is only now obtainable for free. The modest Atmel chipset price includes the ZigBee stack under sub-license at no additional charge. Other vendors are sure to follow suit.

For hardware, ready-built PCBs in the form of evaluation kits are the easiest approach. Transceiver boards from Chipcon with the CC2420 are $50 each. Freescale’s 13192DSK evaluation kit with a microcontroller implementing an 802.15.4 MAC and RS-232 interface costs $200 a pair.

There are a number of options for building your own hardware at a much lower cost. The components alone are less than $15 per node in low quantities. Refer to the Resources section if you’re interested in obtaining the schematics, BOMs, and PCB layouts.

Several vendors currently offer full-featured ZigBee development tools for the higher layers, but they’re expensive. Sounds like an excellent idea for an open-source community-based project! In the meantime, you can use the same physical layer that ZigBee uses along with the free MAC source code from Chipcon and Freescale. You can do a simple star topology network using the MAC layer and a few of your own functions to complete a rudimentary ZigBee-like network. If you take this approach, your hardware will be fully ZigBee-compatible. If you plan on applying more sophisticated software as it becomes easier to obtain, you can begin ZigBee development immediately. Do you act now, or do you let the ZigBee zephyr pass you by?