DeviceNet and the Zombie Apocalypse

Many a year ago, in a faraway place, I attended an ODVA conference (Colorado I think, but that’s not important). Unbeknownst to me my boss was crafting a plan. Let’s call him Rohn Jinaldi to keep his anonymity. Never one shackled by mainstream ideologies or decorum, he crafted an article meant to be controversial while still invoking conversation and sent it into the world. “DeviceNet is Dead!” he proudly proclaimed.

Now John (I mean Rohn) was merely pointing out that factory floor technology was changing, Ethernet was becoming established as a viable solution in the factory and DeviceNet’s successor EtherNet/IP was preparing to take its rightful place on the Mount Rushmore of Industrial Protocols.

Without revisiting the article, let’s just say it hit a nerve. I had the top brass at ODVA stopping me in the halls between technical tracks and training seminars asking, “What was he thinking?” and “Did he really just write this?”. Having not read the article, I relied on my blissful ignorance for the rest of the week. It made for quite the interesting conference and I still hear about it periodically in my travels for ODVA events.

This story has a happy ending since DeviceNet is still alive and kicking. OK, so maybe it is living in an assisted living retirement home. Enabling companies like RTA still sell DeviceNet software (#WannaBuyDeviceNetFromRTA), ODVA still tests devices and vendors still sell those devices. No, DeviceNet isn’t poised to reclaim its spot at the top of industrial protocols, but it isn’t fading away to obscurity.

DeviceNet still boasts the many features that made it popular when it was first designed.

  • You can run the communication wires and power wires together in a single shielded cable.
  • You can run your trunk lengths at up to 500m for 125K baud with 6m per drop for each device.
  • The baud rates vary from 125K to 500K, so you can get roughly 4000 eight-byte data messages every second. Not fast by today’s standards, but not too shabby when the technology was designed in the 90’s.
  • The Master/Slave paradigm allows a single device (usually a PLC) to send periodic messages with output data to up to 63 slave devices, which in turn send back input data.
  • You can mix control/status data with your configuration and diagnostic information on the same wire using CAN’s built in prioritized transfer mechanisms.
  • The network supports adding and removing devices while the network is powered.
  • All devices support duplicate MAC ID (node ID) detection to ensure two nodes don’t share their MAC ID

Many factories are reluctant to switch to the latest and greatest technologies due to the high costs. Maybe DeviceNet is just the protocol you are missing in your product offerings.

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