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Fieldbus Over Ethernet Without a PC Card

Computing trends drive the development of Hilscher’s netHost Fieldbus Master, which is designed to provide fieldbus communications over Ethernet connections to the latest computers, which increasingly lack a PC card slot.

The netHost Fieldbus Master
The netHost Fieldbus Master

While visiting the Hilscher booth at the 2013 SPS/IPC/Drives show in Nuremberg, Germany, I received updates on several technologies we’ve been following over the past year or so, such as Hischer’s functional safety partnership with Mesco and its netTap product for protocol conversion.

A new release showcased at the Hilscher booth that caught my eye was its netHost Fieldbus Master, a module that provides connection to and control of fieldbus systems over Ethernet. While there are plenty of products out there to do this, what sets netHost apart is ability to do this on a computer without a PC card slot. Just as new computers are arriving without a built-in DVD/CD drive, slotless systems are becoming more ubiquitous in embedded computer systemsas well as in laptops, industrial compact computers, and HMI panels.

According to Armin Beck, product manger at Hilscher, the new netHost family allows users to control fieldbus systems using a standard Ethernet port.  The netHost works in the existing infrastructure and can be directly connected with a network cable, or with switches, over VPN connections, over the Internet with routers, and in wireless networking.

The TCP/IP-based open transport protocol in netHost transmits underlying I/O data as well as the acyclic services for fieldbuses such as DeviceNet, Profibus and CANopen. To enable integration into existing systems, netHost includes Fieldbus Configuration Software, a Windows DLL for direct programming, a test program of all functions, and an API interface description. For embedded users, there is a C toolkit as well as disclosure of all fieldbus services and the Transmission Protocol source code.

Though fieldbus configuration software is included, Hilscher notes that your own configuration software may also be used to configure a device using XML files. Templates are provided to aid this process. When using your own configuration software a converter component can be integrated to generate the final binary configuration files in the correct format.

Two Ethernet devices can be coupled in device redundancy mode using netHost, allowing for a controlled switchover in the event of a device failure or loss of connection. Using a removable SD card with netHost, a replacement device can be brought back into operation using the original configuration image.

Beck said that Hilscher developed netHost in direct response to a market need. “For 15 years, one of our customers, a major industrial automation supplier, had been using a Hilscher PC card to facilitate Profibus communications with the I/O,” he said. “A recent design change in their VxWorks-based host PLC system eliminated the card slots to make it more compact and cheaper. This change made the use of plug-in communication cards impossible.”

By developing netHost to address this issue, the new PLC can continue to support of the legacy Profibus communications.

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