You know the old saying: “The great thing about standards is that there are so many of them.” One of the barriers to the growth of home automation is that there are many competing standards and none seems to talk to the other. In addition, communicating and controlling these “standards-based” devices from a computer usually requires custom drivers for each protocol, and often each device.
In a perfect world, consumers should be able to buy products from a variety of vendors and have them “automagically” communicate together and dynamically show up in the computer.
What is needed is a common way to abstract the characteristics of each device in a “standardized” way so that one vendor’s device can be seen and controlled by another vendor’s automation software without having a custom-developed “translator” between them.
We are now one step closer to that dream, thanks to a new bridge from Archronix (ARCX) that links ZigBee with Web Services for Devices.
ZigBee is a low-rate protocol for automation applications. In the home automation business, versions of the protocol are used by such companies as AMX, CentraLite, Control4, Crestron, Eaton and Xantech.
Web-Services for Devices is an initiative by Microsoft and other industry leaders to standardize how devices communicate over an Internet Protocol network. With WSD, devices describe their capabilities to other networked devices, allowing for easy deployment, discovery, and control on the network.
Archronix brings these technologies together with the ArcWay ZigBee-WSD Gateway. The Gateway will allow WSD enabled controllers such as Windows Vista PCs, and Exceptional Innovation’s Lifeware automation software to communicate directly with ZigBee-compliant devices with no additional device drivers or setup.
To demonstrate the capability of ArcWay, Archronix has developed a ZigBee-enabled light dimmer, ArcLight, that has been demonstrated to integrate smoothly within a WSD environment.
On ZigBee and WSD
ZigBee is designed as a low-bandwidth communications protocol for devices requiring very low power, such as sensors, light switches and remote controls. The ZigBee standard consists of two primary elements:
1. IEEE 802.15.4 Wireless Communications – The wireless transport that allows the ZigBee devices to communicate with each other.
2. Application Profiles â€“ What the devices say to each other once they are connected. ZigBee has a variety of pre-defined Profiles for different device implementations. For the light dimmer, it uses the associated pieces of the ZigBee Home Automation Profile. From a software perspective, different vendors’ products that perform the same functions all expose their capabilities and attributes in the same standardized way. If your ZigBee control point or software can control a light dimmer from one vendor, it can control another vendor’s the same way without requiring customized software for each one.
The goal is to install a light dimmer in the home and be able to interact with it securely and automatically. This way a computer can discover it, find out what services it offers, and control it without a custom driver or control software.
The new suite of Rally technologies found in Microsoft’s Windows Vista operating system enables this integrated functionality and multi-vendor communications. Rally encompasses a wide base of technologies used for discovering and communicating with a myriad of devices dynamically connecting to the Vista ecosystem using industry standard protocols.
This integrated ecosystem is built on an inter-related set of communications protocols under the Web Services umbrella. The The World Wide Web Consortium (W3C) defines a Web Service as “a software system designed to support interoperable machine-to-machine interactions over a network.” Two standards most applicable to both Vista’s Rally technologies and the ArcWay are:
A. Web Services for Devices (WSD) – An implementation of the Devices Profile for Web Services (DPWS) specification that enables devices to interact with Microsoft Windows over an IP-based network. WSD’s Function Discovery and Publication Services provide a way for devices to expose what capabilities it supports and what is discovered by the computer. In addition, WSD:
Â· Defines how devices can use Web Services.
Â· Supports resource-constrained devices (little RAM or processing power).
Â· Ensures interoperability between devices and PCs.
Â· Enables device and service discovery.
Â· Supports subscriptions and eventing.
Â· Provides for the exchange of rich metadata.
Â· Builds on standards and Web Services specifications.
B. Home Automation Web Services Description Language (WSDL) Templates for Home Automation â€“ Extensible Markup Language (XML) documents that describe the communications agreement (or “contract”) between network end points and define the interfaces (web method calls, events, etc.) for the device. This standardized WSDL document is the key to the interoperability between the devices, the objects in the computer representing those devices, and the graphical representations of those devices through the User Interface. The WSDL Templates for Home Automation consist of three key sections:
Â· TYPES â€“ Defines the operational parameters (or variables) of the device and holds the Extensible Markup Language (XML) Schema data type definitions.
Â· MESSAGES â€“ Defines the input and output messages used by Operations (below) for sending and receiving data. These generally are based on the defined Types above.
Â· OPERATIONS â€“ Defines the Message exchanges (web method calls) supported by the device.
In short, the WSDL is the WSD interface definition that describes the device’s Web Services interface to the outside world. It is an XML document used by the vendor’s development tools for creating an executable binary. Communications with device’s Web Services interfaces uses XML-based messages (defined in the WSDL) to pass data, invoke methods, and raise events (through an event subscription facility). In practice, the WSDL is published by the web service designer (in this case, ARCX) and represents the binary implementation other vendors can use for communicating with the device’s Web Services interfaces.
ArcWay as Gateway
ArcWay is a platform that manufacturers can leverage as they build products that need to connect and interact with other devices on the home network. If a ZigBee End Device (ED) complies with the Automation Profile at the Application Layer, then applications built on Vista will discover it via ArcWay.
Unfortunately, the current versions of Vista still do not yet have a Lighting Template available, so it does not work as natively as a printer or scanner device, which already have templates defined. However, these capabilities will be incorporated into a future release. As Vista incorporates these new features, it will have the native-mode capabilities for applications to take advantage of this new platform. Conversely, as the ArcWay matures, it will interoperate with even more ZigBee devices by recognizing a larger set of ZigBee Profiles.
ArcWay ZigBee/WSD Gateway
1) The light dimmer [A] (called a ZigBee End Device or ED) communicates wirelessly over the 802.15.4 transport [B].
2) A ZigBee Coordinator (ZC) is used to configure the ZigBee 802.15.4 Wireless Interfaces on both the light dimmer [C] and on the ZigBee side of the ARCX Gateway device [D] so that they can communicate with each other.
3) The light dimmer and the gateway then “talk” to each other at the ZigBee Application layer. They both “understand” the ZigBee Automation Profile mentioned previously.
4) On the other side of the gateway is an Ethernet connection [E] that communicates with a Vista PC over the home network. There is a WSDL Protocol Stack in the gateway [F] that “talks” to the Rally and WSD Application Programmer Interfaces (WSDAPI) on the Vista PC [G].
5) The light dimmer device shows up as a new device in Vista and asks for permission to communicate with the PC (a requirement from a security perspective).
6) The light switch then is available as a controllable device from within the Windows Media Center User Interface.
From an application and control perspective, the gateway then “translates” the communications from the ZigBee Profile-based messages to XML Schema-based messages compatible with Web Services for Devices. As an example:
ArcWay as Translator
1) The light dimmer [A] sends an OFF status message [B]. The message has a defined format that follows the message structure of the ZigBee Home Automation Profile.
2) That OFF message gets “mapped” to the appropriate XML message defined in the WSDL for a Lighting Dimmer device [C].
3) The WSD interfaces built into Vista [D] recognize the “OFF” message associated with the Lighting Dimmer object [E].
4) The User Interface for the light changes on the screen to show that the light is off.
The gateway is bi-directional. It translates messages both to and from the device and the PC. Other examples of commands are Ramp Up, Ramp Down, Ramp to Level, Goto Level, etc.
As a side note, technically the Vista User Interface subscribes to a state change in the light dimmer from the PC. The notification it receives would be an event corresponding to that subscription. The ArcWay facilitates both environments communicating at that level.
ZigBee-to-WSD: The Potential
ArcWay is the start of a new wave of interoperable products for the home integration and automation market place. Whether you are buying and installing light dimmers, thermostats, Heating, Ventilation, and Air Conditioning (HVAC) controllers, window sensors, or shade controllers, you want to make sure they can talk to each other using defined industry standard communications interfaces â€“ and without requiring specialized drivers or software.
The Archronix ArcWay ZigBee to WSDL gateway allows two sets of standardized yet disparate technologies to communicate with each other. You can buy products from a variety of vendors and they will be able to plug and play together. They will show up as controllable devices on the computer and you can interact with them through the Media Center User Interface. Not only that, it enhances any devices’ usability by allowing it to be configured, controlled, and scheduled through a familiar PC interface.
You can do more than just turn a dimmer on and off. Vendors can add capabilities to devices that the device itself may not support natively like scheduling or interacting with another device’s status or events. For example, even if the dimmer device itself does not support scheduling or binding to something like the window shades, these rules could be maintained and executed on the PC side, thus creating added value for the consumer.
The ArcWay is scheduled for release in the first quarter of 2007. There is no price available at this time.
About Archronix Corp. (ARCX)
Archronix Corporation (http://www.arcx.com/) is a technology design and product engineering firm specializing in hardware control systems and the associated enabling software. Archronix has taken its expertise in embedded processor and Windows application work and extended it into connected devices in the home. The company provides product development and integration services for several OEM clients in Canada and the US. Much of ARCX’s current work includes connectivity to and integration with Windows Media Center for both high-end audio and audio distribution systems.
Archronix is responsible for creating the Media Center interface for Magnum Dynalab’s MD109 high-end radio tuner in addition to Ethernet control for the Matrix MiSeries audio distribution controller.
About the Author
Derek R. Flickinger is vice president of R & D for Interactive Homes, Inc. (www.InteractiveHomesInc.com) He provides consulting and implementation services for manufacturers and consumer electronics installation companies on new technologies, products, and strategies related to standards-based Distributed Audio, Video, Communications, and Control (DAVCC) systems for the home and consumer market spaces. Derek’s long-term goal is to be instrumental in the development and deployment of entertainment systems on space stations and space colonies.