Appliance Design - October 2007 - (Page 35)

ELECTRONICS including Wi-Fi and Bluetooth. In fact, typical home automation/entertainment products often build in both Wi-Fi and ZigBee in the same device. ZigBee defines three different types of nodes: ZigBee Coordinator (ZC), which is responsible for initial configuration and continuing control of the network; ZigBee Router (ZR), which can relay and/or respond to messages in the network; and a ZigBee End Device (ZED), which can send and receive, but not relay messages. There is one coordinator in each ZigBee network, and in typical home networks, this may reside in the electric meter, home gateway, or central home automation controller. Any device may be a ZigBee router, though these are generally line-powered devices, as they need to be continually active in order to forward messages through the network. The simplest ZigBee devices are the ZEDs, which may implement various sleep modes in order to allow a very long operating life with low-cost batteries. ANY PROCESSOR APP APP … APP APP … APS APS SSP SSP NWK NWK MEDIUM ACCESS (MAC) MEDIUM ACCESS (MAC) ZDO USER APPLICATION ZigBee STACK MAC+PHY Fig. 4. SoC vs. ZigBee coprocessor functional implementations. ZigBee SoC ZigBee Network Coprocessor PHYSICAL RADIO (PHY) PHYSICAL RADIO (PHY) Implementing ZigBee Even though the ZigBee protocols are quite sophisticated, ZigBee can be fully implemented with low-cost analog/digital hardware and software running on a small microcontroller. Most designs use single-chip SoCs (systemon-chips), that integrate the IEEE 802.15.4 radio, MAC, embedded microcontroller core, AES encryption engine, RAM, Flash, and peripherals for SPI, UART, I2C, GPIO, Fig. 5. Typical ZigBee radio module with internal antenna and external connectors. www.applianceDESIGN.com ADC, and timers. Very few external components are required. The ZigBee stack runs as software on the core and is stored in the integrated Flash memory. The device application (such as a wireless light switch, temperature sensor, load switch, etc.) is also compiled to the embedded core, sharing cycles and memory with the ZigBee stack. Sometimes a separate microcontroller is desired for the device application, such as when ZigBee is being added to an existing design, or when the application is reasonably complex. Here, a ZigBee network coprocessor may be used. In this case, the device application interacts with the ZigBee stack (fully implemented in the coprocessor) via a simple serial (SPI or UART-based) interface. These options permit ZigBee connectivity to be added to existing smart-appliance designs in a relatively simple and straightforward way, and at low additional cost. Many designers with extensive experience in embedded microcontroller and software development may not have experienced the challenges of implementing RF radios in their designs. A poor RF design will dramatically impact the range and reliability of the final product. Fortunately, most ZigBee suppliers provide complete and proven reference designs for a wide range of different application scenarios, greatly simplifying this part of the design. Partners of these suppliers can also offer design services or even complete, low-cost modules that make implementing ZigBee that much simpler. To assure interoperability with other ZigBee devices at the protocol level, and to earn use of the ZigBee Alliance logo, designers must start with a ZigBeeCompliant Platform, consisting of the SoC or coprocessor hardware and the software stack, that has been tested by one of the Alliancedesignated test houses. Use of the ZigBee-defined application profiles, such as the Home Automation profile, additionally assures interoperability at the device message level, and allows designers to have their end products tested as ZigBee Certified Products. ZigBee has prevailed over earlier proprietary offerings for HAN and advanced home automation applications not only for technical superiority, but also because it is an open, multi-vendor standard that provides designers many choices of platforms to use. There are several important questions to consider when evaluating ZigBee platforms: 4What is the maturity of the platform implementation, especially relative to the enhancements offered in the latest ZigBee specifications? 4How robust is the ZigBee stack implementation? Has it been adopted by many of the providers of HAN and home automation systems vendors? 4How capable are the hardware and software tools provided as part of the platform? Virtually all vendor development kits are easy to use out of the box, but are they easy to use when testing a complex network of many nodes? The right choice of platform can assure a successful ZigBee implementation. While smart appliances have proven to be a boon for consumers, smart appliances that communicate will enable societal benefits as well as greater convenience to consumers. With the emergence of complete platforms implementing the ZigBee wireless standard, designers can now deliver these benefits simply and cost-effectively. And perhaps now the fully connected home foreshadowed by the Internet toaster will be viewed with even more amazement, and far less amusement. < For more information, enter . . . . . . . . . . . . . . . . . . . 307 Or email: sales@ember.com applianceDESIGN October 2007 35 http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - October 2007

Contents Editorial Shipments/Forecasts News Watch Applying Powder Coatings to Plastic Parts is No Longer a Pipe Dream New Technology Platform Provides the Ability for a single IC to Control Two- Motors in a Single Appliance, Simplifying Motor Control Design Advanced Motor-Control Techniques have Become More Accessible to a Wider Array of Appliances, Helping to Improve Efficiency and Reduce Noise Adding USB Host Capability to Appliances Permits In-Field Programming and Acquisition of Test Data ZigBee Modules Make it Easier to Design Wireless Connectivity into Applications New Concepts such as Rapid Tooling and Rapid Injection Molding Provide Stepping Stones Between Prototyping and Full Scale Production A Number of Factors and New Developments Affect the Decision on Whether to Build Prototypes In-House or Outsource to a Service Bureau DesignMart Advertiser’s Index Association Report: CEA

Appliance Design - October 2007

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