How Tesla is replacing the age-old CAN bus | Hacker News Reader

How Tesla is replacing the age-old CAN bus

notateslaapp.com

18 pointsKnuthIsGod59 comments

This is just what we need: "From the same guys that brought you the Cybertruck, comes a new replacement protocol [for a tried and true thing that's been running for decades] ..."

I really hope the industry sits this one out or, if needed, comes up with something better.-

It's also "From the same guys that brought you the Tesla Model S, 3 and Y". It's easy to point the finger at a bad product a company has made and throw out all of the good.

The new CAN looks to include tried and trued protocols that have existed for a while but would allow for a much better system.

The combustion engine was tried and trued and didn't need changing until someone decided to do something better and electric engines are better.

What a bad article. Why would you want to stream video over CAN? Also, alright, so Tesla has invented Flexray, MOST and AVB. Congratulations?

> What a bad article. Why would you want to stream video over CAN?

Rear video feed

I am aware that there's video usecases in cars, but why consider CAN for that at all? That's like streaming music via UART - yes, can be done, but why.

If you can't get rid of CAN completely, I believe the advantage to cramming as much stuff on there as possible is to reduce the amount of wiring.

"CAN FD barely makes the mark for 1080p video streaming at 60fps"

Maybe use CAN for what it was intended and add any new, proprietary high-speed video stuff on the side?

This. An extension or annex. Does every protocol needs to end up streaming video? Even industrial-grade stuff?

Ah, yes, industry. A place where, famously, eyes aren't used because they're not rugged enough.

Heh. That's what we need :)

Ruggedized eyes.-

PS. Wonder if such a thing exists in nature ...

Indeed. What's wrong with just sticking a usb-c hub in the cars for entertainment stuff? Oh and disconnect it from the vehicle control.

Right? Or an optical network, just for that high bandwidth, "modern" stuff ...

... but for goodness sake, leave good enough alone for critical stuff.-

The high speed bus should be optical.

They should mandate glass fibers.

Thunderbolt 5 can handle a dozen 4K/30fps streams off a single copper cable.

The limiting factor is the available compute not bandwidth.

It's not about bandwidth; combustion engines used to be massive EMI disasters (due to ignition coils) wrecking electronic communications in their immediate vicinity. Fibre optics are plain noise immune. Not sure how much of this is needed with high power electric motors.

They're also lighter than copper cables, which can in fact matter in a car (though changing interconnect types and topologies also fixes that.)

Electric motors are - almost by definition - giant, fast moving magnets. That will generate current in any nearby wiring, and thus interference.

That said, this kind of interference is much easier to filter than the kind you'd get from 4 to 8 spark plugs firing in sequence. So it's pretty likely that this is easier to deal with.

Are fiber optic cables flexible and tough enough? Fiber optic seems to be good for fixed deployments but not exactly fit for a rough&tumble environment like a car.

Short answer: yes.

Long answer: you need to choose appropriate connectors and fibre types. There's more to fibre than just OM5 and OS2 on LC connectors. Disaster recovery agencies as well as militaries use fibre cabling in temporary camp / communication infrastructure setups too, with ruggedized cables and connectors. There's 50+ years of history and experience to source from.

"Counter" answer: copper cables in cars also break.

Currently to avoid Radio Control in Ukraine they have drones controlled using fiber cables.

https://defence-blog.com/drones-guided-via-cables-change-bat...

No no no... Like Cybertruck, they're doing something amazing, so we should let them do whatever they do without limits. (obvious angry satire warning if it's not visible already).

Maybe they should add some efficiency in to the protocol, via their newly obtained cross-discipline expertise.

And the protocol shall have no logging capabilities.

Oh, it should log.-

To DOGE.- /s

> add any new, proprietary high-speed video stuff on the side

Dashcams just use regular USB-C with HDMI or DisplayPort.

And the electronics for this are cheap, plentiful and reliable since it is used extensively in hobbyist circles e.g Raspberry Pi. No need for anything proprietary or crazy. Just run another cheap cable.

CAN bus never was the only choice of automotive buses, it's the cheapest option. There were always competing standards like FlexRay and LIN buses, just like there were Rambus RDRAM against JEDEC SDRAM or IEEE1394 against USB.

It's what Mercedes pioneered, and what most high-volume manufacturers standardized on, including most Japanese and American brands. Some European companies like Volkswagen-Audi Group uses something else. I think implication of that is clear.

Nissan and Toyota had been shipping cars with automotive Ethernet since as early as 2019. Including Toyota's Hydrogen EV since at least 2022. I think implication of that is also clear.

LIN is simpler and less capable than CAN, to the extent CAN is cheaper at this point, it is because it has so much more volume.

IEEE-1394 has(d) all the logical properties this article attributes to ElonBus and it's 30 years old.

Can also run over optical.

Another take on the headline:

> Tesla replacing common bus with wide range of somewhat interoperable tools with own proprietary bus no one else will be able to talk to

Can't we just use Ethernet instead?

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.

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.

> 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).

Nobody ever tried to use CAN for streaming video, because that’s not the purpose of CAN?

> Tesla’s next-gen networking is all about timing - and unlike CAN, where two messages coming in at the same time can collide (resulting in neither reaching the node),

> CAN is like everyone yelling in a room

This is simply false. CAN uses bit arbitration and the lowest address wins.

> CAN uses bit arbitration and the lowest address wins.

And in doing so it prioritizes important messages and enables deterministic timing.

> Nobody ever tried to use CAN for streaming video, because that’s not the purpose of CAN?

How do the reversing/parking cameras work then? I always thought the reason why their feed is so low quality even in new cars was because they transmit through CAN.

The cameras often have dedicated cabling to the front. Sometimes analog video (probably not so much today, or only on the cheap end), sometimes digital over Coax. In other cars its using Flexray (which is a high-performance bus-system designed to be able to also support video)

I'm also sure somewhere Doom is running on CAN.

Can’t wait for their shitty half baked software to break something critical hanging off the same bus as the cameras.

(Ex model S owner - would never touch another thing they went near again)

cant read stuff that is in between ads.

Is this a website that's entire purpose is to shill for Tesla or have I become too cynical?

This article for example was written to debunk Mark Rober's video on Tesla and collision avoidance: https://www.notateslaapp.com/news/2609/new-wile-e-coyote-wal...

But the arguments made against it seem quite biased towards Tesla: "However, this entire test scenario is so out of left field… there is a good likelihood this same test would fool some human drivers as well"

When one of the major arguments of the video was about easy and affordable it was for the average LIDAR system to detect the wall. Of course human beings are not perfect drivers, which is why Tesla's attempt at mimicking human senses for its self driving capabilities is a bad idea. But the article seems completely ignorant of this IMO very clearly stated narrative in Mark's video.

> But the arguments made against it seem quite biased towards Tesla: "However, this entire test scenario is so out of left field… there is a good likelihood this same test would fool some human drivers as well"

The argument seems to be that running the test with FSD rather than Autopilot lead to much better results:

> During this test, many people noted that Mark was using Autopilot rather than FSD...Creator Kyle Paul over on X made a much better follow-up video, using both a HW3 Model Y as well as an AI4 Cybertruck. In a relatively unsurprising turn of events, the Cybertruck was successfully able to detect the wall, slowed down, and came to a stop. The Cybertruck was running FSD 13.2.8.

That seems like a valid point. Saying that you're testing Teslas self-driving car and not actually testing FSD but opting for the less advanced Autopilot feels misleading.

Okay FSD is better than autopilot. If we put aside Tesla-specific marketing terms, and you had an unnamed car company advertise a feature called autopilot, would you as a customer expect the car to stop when met by a wall? I wonder how it would fly in court.

More like can't bus, amirite?

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