Single Pair Ethernet - How to network an airplane

IoTPanic · September 3, 2020

Hey all, was making some PCBs around a relatively new standard and I thought it was cool so for others I thought I'd share. This isn't related to your home gaming computer or whatever but you might find it interesting. I think a techquickie would be neat for one of those days they're out of ideas.

Unless you wanted to run fiber everywhere, which in the situations we're about to get into is impracticable, or deal with the headaches of wireless communication, the trusty traditional Ethernet cable is used to network two machines together. Not only is this solution fast, achieving 10Gbps on Cat6, but power can be provided for edge equipment along with the data one a single cable.

Modern cars, airplanes, and massive factories require the networking of potentially thousands of devices within a confined space, the eight twisted conductors of traditional Ethernet cabling, along with the sheathing of the cable is not only expensive in this case, but in many situations just cannot fit. This caused many industry leaders to involve the IEEE who developed a new standard called single pair Ethernet, or SPE. Under this 802.3bp standard both a 1Gbps link along with power can be sent over only two matched conductors, greatly reducing the width of each run. Most ICs that are developed by companies like Microchip are 100Mbps, but are incredibly inexpensive with few external components, making it cheap and easy to deploy massive sensor networks, run the ~3km of cabling within a car, or connect all the entertainment systems to watch movies inside airplanes. Additionally, the connectors used are not the standard RJ45, but typically a tiny two position locking connector that takes inspiration from the LC fiber connectors making the switches connecting it all together smaller.

While you might not see the standard in your house, there might be a day where a niche IP camera you buy doesn't have the familiar RJ45 jack, but rather an odd tiny two position connector instead.

igormp · September 3, 2020

I've worked on an automotive research lab before and had the opportunity to do some projects with 100Base-T1, and even had the chance to toy with a prototype 1000Base-T1 board from marvell. I couldn't believe that it managed to do gigabit over a single pair until I actually plugged the other side into my laptop and did an iperf haha

The standard I'm most excited for is actually 802.3cg, which only does 10mbit, but is actually meant to be run on a bus topology, which could work perfectly fine as a CAN replacement.