How Tesla Is Replacing the Age-Old Can Bus
52 comments
·April 21, 2025alternatex
gonzobonzo
> 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.
alternatex
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.
Bluestein
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.-
damnitbuilds
"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?
threeseed
> 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.
Bluestein
This. An extension or annex. Does every protocol needs to end up streaming video? Even industrial-grade stuff?
detourdog
The high speed bus should be optical.
threeseed
Thunderbolt 5 can handle a dozen 4K/30fps streams off a single copper cable.
The limiting factor is the available compute not bandwidth.
eqvinox
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.)
bayindirh
They should mandate glass fibers.
bayindirh
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.
Bluestein
Oh, it should log.-
To DOGE.- /s
aaron695
[dead]
lpcvoid
What a bad article. Why would you want to stream video over CAN? Also, alright, so Tesla has invented Flexray, MOST and AVB. Congratulations?
xnx
> What a bad article. Why would you want to stream video over CAN?
Rear video feed
lpcvoid
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.
xnx
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.
numpad0
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.
maxerickson
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.
jauntywundrkind
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
amelius
Can't we just use Ethernet instead?
throw-qqqqq
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.
Muskisapuss
Srsly? The most common standard known to mankind, with one of the cheapest components needs 'much more'?
Feel free to elaborate how basic ethernet would cost relevant much more than pushing video through CAN.
throw-qqqqq
Yes very seriously.
Many microcontrollers come with CAN support natively, but no PHY for instance. So CAN is available for even the cheapest MCUs, not so with Ethernet.
There is also a lot more supporting hardware required for Ethernet compared to CAN, and the price for producing a cheap Ethernet capable board is many times that of CAN.
The galvanic isolation in Ethernet (magnetics) costs about 1W idle pr port, so the power budget is also on a whole other level.
I spent the previous decade in embedded, designing both CAN and Ethernet-capable cobtrol systems for industrial applications.
Ethernet is much more expensive than CAN, but can also be much faster etc.
CAN and Ethernet normally do not compete for the same applications :)
liamkinne
Have a look at Ethercat. Based on the same physical layer as Ethernet but allows daisy-chaining devices.
camtarn
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?
eqvinox
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
formerly_proven
The short-reach single pair Ethernet (xxxxBASE-T1) is largely developed for automotive and robotics, yes. Also supports PoE.
throw0101b
> 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-...
jeffbee
IEEE-1394 has(d) all the logical properties this article attributes to ElonBus and it's 30 years old.
detourdog
Can also run over optical.
fabiofzero
More like can't bus, amirite?
retinaros
cant read stuff that is in between ads.
ohgr
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)
formerly_proven
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.
smnc
> CAN uses bit arbitration and the lowest address wins.
And in doing so it prioritizes important messages and enables deterministic timing.
black3r
> 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.
detaro
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)
detourdog
I'm also sure somewhere Doom is running on CAN.
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.