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KNOCK! KNOCK! "WHOýS THERE?"

Using UPnP to Respond to Inquiries
by Edward F. Steinfeld

Start ý UPnP Overview ý Functions ý Device Addressing, Discovery, and Description ý Control, Event Messaging, and Presentation ý UPnP Forum ý Software Tools ý Hardware ý Easier Deployment ý Sources and PDF

What machines are on the Internet? What is their status? How are operations controlled on the machines? Will the machines notify when they have a significant event? Is there a simple human interface for the networked machines? These questions are handled with the network Universal Play and Play (UPnP) technology standard.

The network shown in Photo 1 is a factory (PLC, machine tool controllers, conveyor belt, controller), but it can be used in any one of the following:

• hospital lab (cell counter, chromatograph, blood analyzer)
• office (print server, fax, DSL router, HVAC controller)
• home (set top box, appliance, audio system, HVAC, security)
• process plant (setpoint controllers, smart sensors, PLC)

Photo 1ýUPnP-enabled devices and control points on a factory network. When a new control point (laptop) is added, it may inquire of the network to find UPnP-enabled devices (machine tools). These devices respond with their URL and device description. The control point then can obtain the status of each machine.

These UPnP smart machines, called devices, are in a local network connected using TCP/IP and communicate with a UPnP control point. The control point could be a cell controller, the operatorýs station, or just another device on the network.

Along comes your supervisor, who connects his or her laptop either directly into the hub, via 802.11b, or maybe even remotely across the network. Your supervisor wants to know what machine tools are running and the status of each. Or, another device on the network is powered up for the control point to recognize. This knowledge of the active devices on the ýNet can be determined if they are enabled using network UPnP.

In this case, the laptop is a UPnP control point, which can query the network devices for status and receive transmissions from each device that include a description of the device and a pointer to the deviceýs URL.

Note that as of today there are no templates or standards for how industrial machine tools will communicate data using UPnP. Templates are created by UPnP working committees, and a number of templates do exist. Invensys has approached the UPnP Forum to create an industrial working committee to define templates for factory and process plant usage. Templates provide for interoperability of manufacturers of similar devices with control points. You can still implement UPnP on the factory floor, but it will have to be without the comfort of a common standard of data identification.

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