WHY CHOOSE ZigBee?

Figure 8 shows where ZigBee sits in the pool of current and emerging wireless standards. The “hobby ability” color scheme indicates the likelihood of your being able to use the technology in projects for less than $15 while being able to wire and code it into a project. The $15 figure is a one-off cost, assuming you make your own two-layer PCB. Green on the hobby ability scale means the technology is in a format you can use without having to be one of the select few beta-testing partners of a silicon-forging research company. Beige means it’s emerging or isn’t in a format in which you can directly integrate the chipset to a low-end microcontroller for less than $15.

The newer the technology, the higher the initial cost, and the higher the risk that it won’t become popular. For example, 802.11 used to be technically superior but a little too expensive and complicated to hook up to my PIC-style microcontroller. Today, things are different, but the price remains higher than $20 and it won’t fit key fob-sized applications. The cost of a naked ZigBee IC plus the necessary discretes beats those options on physical size and cost if you want to hook it up to a simple 8-bit MCU. However, ZigBee doesn’t compare when it comes to data rate.

At the other end of the spectrum are simple transceivers that use rudimentary modulation techniques such as OOK, ASK, and FSK. These are easy to use for simple point-to-point links, but anything more complicated requires you to write a complicated protocol to be run in parallel with your application. Some of these low-cost transceivers are frequency-agile enough to implement simple FHSS. But again, implementing this yourself isn’t trivial and almost certainly demands a dedicated base band microcontroller. Even an expert could spend several months setting up the transceiver and coming up with a workable solution for the first few layers of the protocol stack.

For ready-to-go proprietary spread-spectrum solutions, MaxStream leads in the field with the most affordable spread-spectrum radio modems. The 9Xcite 900-MHz wireless OEM module is $48 in single quantities ($34 in volume). They’re easily configurable in point-to-point or point-to-multipoint modes, and they operate transparently with an RS-232, RS-485, or USB interface. This is the option to choose if your focus is to get something working within 30 min., and you want an FCC pre-approved solution. The price of proprietary spread-spectrum solutions has dropped over the last two years. If you need to increase the range to several miles in one hop, there are simple upgrade options for that too.

ZigBee’s range is restricted to your house or office. It isn’t designed for a high data duty cycle from each node. ZigBee is much less mature than proprietary spread-spectrum solutions. However, ZigBee might be a better option if you require the following: small size, cost sensitivity, low latency, low power, and interoperability. But the biggest reason to choose ZigBee is by far the wow factor of implementing cutting-edge technology that is the next big thing.