Single Pair Ethernet Driving IP to the Edge (Part 1)

Single Pair Ethernet blog part 1

Ready or not, soon we’ll have Single Pair Ethernet (SPE): a twisted pair cable carrying both power and data. SPE is smaller, lighter, cheaper, and easier to deploy and supports daisy-chained configurations.

If you’ve been around long enough to have more than a cup of coffee in the manufacturing industry, you know that there are some massive changes in how we do things driven by three big trends:

A requirement for massively more data. Most of the large manufacturers – any fortune 1000 manufacturer certainly – are embracing the concept of digitalization. Digitalization (a.k.a. Industry 4.0, Smart Manufacturing, and other aliases) is the concept of measuring machine operation, running algorithms on that data, and making changes to the equipment and/or process to optimize manufacturing output, quality, downtime, and all the rest. Digitalization is useless unless the Internet of Things (IoT) can deliver the vastly higher amounts of machine data required to power the Analytics, Machine Learning, Preventive Maintenance, and AI applications that drive changes to the process. These applications are profligate users of data and perform better with more data – vastly more data than we’ve ever collected before.

The new requirements for autonomous vehicles. All the new systems needed by an AV to understand the environment on the road and make quick decisions demand vastly more data, much faster than ever before. More sensors, more bandwidth, faster networks, and more sensors are required to get that data but without additional expense and weight. The inexpensive wire, connectors, processors, and fast communications systems are easily transportable to manufacturing.

Desire for one technology. Over the last 30 years, manufacturers have put up with mixtures of largely incompatible protocols (EtherNet/IP, PROFINET IO, and Modbus TCP, for example), networks, and systems. Every new production line had new technology that seemingly obsoleted the “new” technology used on the last production line. Manufacturers have to contend with new technologies and all the cost of procurement, spare parts inventories, documentation, and training from all those incompatible systems. Manufacturers have now realized that IP (Internet Protocol) is how the world moves data and information. There is a lot to gain by standardizing on the Internet Protocol (IP) from the Cloud to the enterprise to the control system and all the way to the field sensor. One standard is vastly more efficient and less costly than using a varied set of technologies.

Single Pair Ethernet is the technology that answers these three trends.


Single Pair Ethernet is simply a physical medium for moving bits from one node to another in an Ethernet network. Instead of the four pairs of wires we use for 100 Mbit Ethernet or the eight pairs of wires we use for 1 Gbit Ethernet, SPE uses one pair. And just like those wired and wireless Ethernet networks, there is a specific Ethernet MAC and PHY for SPE.

The SPE Ethernet MAC is similar to other Ethernet MACs. It manages access to the Ethernet network and the other housekeeping needed to synchronize with other nodes on the network. The Ethernet PHY, like other Ethernet PHYs, converts between the analog signal on the wire and the digital bits used by the MAC.

And MOST IMPORTANTLY: there is no difference between the IP packets that move across an SPE network and the IP packets that move across an 802.3 wired or wireless network. They are identical.

As with most of these technologies, it’s easy to get lost in the nomenclature of all the different standards. It is 802.3bp for vehicles, 802.3bw for motor feedback and encoders, 802.3bp for robotics and CNC, and 802.3cg for use in factory automation. There is a 10BASET1S standard to replace serial fieldbuses and a 10BASET1L to replace CAN and CAN/FD. The S is for short-range (25 m) and the L is for long-range (1 km to 1.5 km).


What’s Coming?

In part two, I’ll discuss the issues related to SPE deployment and what the future holds for manufacturers and device vendors.

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