- moving the voltage up means you can drop current
- increase the data rate by using ethernet and PoE
- using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car
- moving the voltage up also means reduced heat produced
I work for another EV manufacturer. Good God I would love to switch from CAN to ethernet. We already have way too many CAN buses and we're considering adding more. But it will take decades for our suppliers to even consider the switch. We just paid Bosch $15M for an upgrade to our brakes, they promised the change in six months, it took them two years and quite a few additional millions of dollars, and it's filled with bugs. We can't even run the new brake firmware on public roads it has so many bugs. And we'll have to pay them millions more and wait months or years more for them to fix their own mistakes. This is why Tesla does almost everything in house. I wish my company had the resources to.
Well, then you should maybe ask why do you need such complexity, when cars 5-10 years did not needed to do exactly same task - taking a person from point A to point B.
First of all, there are regulatory issues, that continually demand more both in terms of efficiency and in terms of safety. System that were innovative 10 years ago are not a requirements and new system are recommended and will soon be required. And that is just for minimal compliance. If you actually want to be up to date on safety systems you need even more.
Second, if you are a company you need to actually sell product. And turns out costumers don't want technology from 10-20 years ago. Costumers actually buy stuff with more technology in it. No matter if people on HN rather drive a Honda from early 90s.
So to just tell a company 'just go back in time and that will solve your problem' is simply not gone convince anybody.
Break-by-wire is pretty standard by now. Unless you have any evidence that the system Tesla uses is worse then traditional automotive CAM and that it is so much worse that there will be lots of Cybertrucks unable to break then I'm just gone go with team of engineers who designed a new system after having decades of experience with the older system rather then some guy on HN.
> using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car
Ethernet isn't a bus, its point to point. PoE over cat5/6 uses 4 pairs of UTP.
so it might be used to join aggregate things together, but it won't be a bus.
Yes, you can increase the datarate, but ethernet is fundamentally unreliable. So you'll need to either strictly manage the bandwidth requirements of attached devices, or put in flow control(expensive) or use the weird "reliable" Ethernet they made for fibre channel replacment ($lol and you need to pay to make it automotive rated)
48v is logical, and a lot of other people are doing it.
PoE is probably stupid
Ethernet makes kinda sense, but firewire would probably be better, its a bus and rated for life critical use.
Ethernet can be used as a bus (see CSMA/CD), but if there are more than 2 nodes, performance of whole bus will go to complete shit and there is no guarantee that an ECU will transmit a single packet during its run, because that CD has no automatic arbitration, it is just random disconnection and try again. Not good for critical things like ABS. That's also whole reason why FlexRay was spawned, because even that FR is inflexible abomination of a protocol it actually guarantees that every ECU on the network will get a time window to transmit its own data.
A lot of the Googleable information seems to be from chip vendors who want to sell those things :) Yeah it's intended for new designs. Fewer wires than the original 10mbps ethernet.
But doesn't that mean a single point of failure, a single network problem stopping the whole car? I guess there must be a historic reason for mostly direct CAN connections.
> using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car
You mean like CAN bus is being used since 1990s? I think that Mr Munro little bit fell asleep and missed whole CAN bus and FlexRay evolution in cars.
CAN bus is still really slow (1Mbps, so bus contention is a problem). Sensors, cameras, AV stuff, etc. can't all live on the CAN bus. Cars are not the same things they were in the 90s.
CAN bus is multi-master access with automatic arbitration between nodes. Something what Ethernet is completely incapable of and that's the reason why CAN bus is here to stay for a long time.
Ethernet needs active switches isolating each branch of the star network from each other. Because Ethernet working in bus mode is absolute joke, slower than CAN bus if you add enough nodes to such network. But when you need to drag all sensors and ECUs to a center of a star where is switch, where is the saving on cables?
Even worse, there is no guarantee that node on such network will be able to deliver message to other node, thanks to CSMA/CD which says Random disconnection if collision. Well guess what? Your wheel just locked during braking and we need to tell that to ABS/ESP unit. When using CAN you can rectify it by using low CAN ID and thus increasing priority in arbitration. When using Ethernet, you are only praying to RNG Jesus.
Yes. Post 2021 teslas have nine cameras scattered all over the body. For AV, Tesla would like to get much higher resolution and frame rates out of them.
- moving the voltage up means you can drop current
- increase the data rate by using ethernet and PoE
- using ethernet and PoE means you don’t have to run one off wires to each device, they can share a bus which results in half the copper being used in a lower voltage car
- moving the voltage up also means reduced heat produced