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Comment by amelius | Hacker News Reader

Can't we just use Ethernet instead?

Vanilla Ethernet requires much more hardware and software (IP stack etc.) to function, than CAN does. It’s just not cost effective for many cars.

Time triggered Ethernet is used in aviation though.

The short-reach single pair Ethernet (xxxxBASE-T1) is largely developed for automotive and robotics, yes. Also supports PoE.

Even single-pair ethernet has one more wire than is necessary with LIN, a common low-speed vehicle bus.

We're talking about replacing CAN here, not LIN.

(You're also technically wrong: both LIN and -T1 Ethernet can share power and data onto a minimum total of 2 wires.)

Have a look at Ethercat. Based on the same physical layer as Ethernet but allows daisy-chaining devices.

Similarly, PROFINET, the confusingly named EtherNet/IP (IP here stands for Industrial Protocol not Internet Protocol), POWERLINK, and others - all based on Ethernet but with a custom protocol layer replacing IP. "We need something that is high speed but also supports rapid deterministic communication" is pretty much a solved problem in the industrial space.

I wonder what Tesla's game is here: is it really just reinventing the wheel, or are they perhaps using higher speed Ethernet as industrial Ethernet tends to still be limited to 100Mbit? Or perhaps it's tightly linked with the proposal to communicate over 48V lines?

Industrial Ethernet uses 100Mb speeds because (and when) those are sufficient for their use cases. There is no technical limitation there. 1000base-T1 (and even 2.5, 5 & 10G SPE¹) show where this is going.

¹ Single Pair Ethernet

Huh, I didn't know single pair ethernet went up that fast - neat! We're still living in the 100Mbit world at my company - and, yeah, it's fast enough for pretty much everything we need.

> Can't we just use Ethernet instead?

Growing trend of it for certain use cases:

* https://en.wikipedia.org/wiki/Ethernet_over_twisted_pair#Sin...

* https://www.keysight.com/blogs/en/tech/educ/2024/automotive-...

Addendum, there is 10BASE-T1S, which uses a single-pair and is multi-drop from that pair:

* https://www.keysight.com/blogs/en/tech/2024/02/8/how-is-10ba...

* https://www.analog.com/en/signals/thought-leadership/why-10b...

* https://www.graniteriverlabs.com/en-us/technical-blog/automo...

In some ways this is going to Ethernet's roots with a common transmission medium (Thicknet, Thinnet).

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