Wiring genius: 48v power + data CAN bus

[flowerlandfilms]

Probably the best doc would be this:

I'd love to see that thing.

SIDE NOTE:
Anyone know what the subtitle says? I'm very curious now. I mean, it has the word BOOBS. Probably in reference to the people not the body parts or the calculator gag.

HOW TO DESIGN A 48-VOLT VEHICLE
(you incompetent boobs!)
[do we really have to do your homework for you]
{ELON XOXOXO}

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[Dazureus]

Maybe they are using Tolkien-Ring networking ?‍

Gimili's gonna bust his axe trying to break the Cybertruck.

 

[Dazureus]

@13:25 Sandy mentions "communication over power" guessing he is referring to PoE and Pete Bannon says "no" they use 2 more conductors then explains they have gigabit ethernet, bi-directional for redundancy.

@19:30 Pete Bannon explains the ethernet comms.....says it "looks like a token ring network" then David Lau explains it's a TDMA(Time Division Multiple Access) network.

@39:15 Sandy and Pete look at the 48V "left controller" Pete points out an ethernet loop connection says it's standard twisted-pair shielded cable.

Also when Ganesh Venkataramanan left Pete Bannon took over the Dojo supercomputer project.

I think it's interesting that they decided to go with TDMA communication protocol rather than normal ethernet packets and a grand master time keeper. To use a common analogy, ethernet protocol is like cars getting on a freeway; all devices just shoot their packets onto the wire with directions where to go in an asynchronous manner. This can cause collisions when two devices try to send packets at the same time since there's no device hierarchy on ethernet. When collisions are detected, both packets are discarded, which can be bad in an automotive implementation.

CAN overcomes this by having a priority arbitration bit field in the message. A CAN message has an 11 bit identification field. The lower the value in that field, the higher priority the message and each device then arbitrates it's sending based on that priority scheme. The messages are sampled synchronously, but sent asynchronously so when a device samples the message on the bus, it will compare the identification field against it's own and determine if it's allowed to send or not. Collision data is preserved in this case.

TDMA is a bit of an older protocol, but ensures data transmission. Basically the communication is divided into time slices, with each device being assigned a slice. Instead of cars cramming onto a freeway, think of train cars being joined together. There's not a ton of information yet available on how Tesla is implementing this, but from the language I've heard so far, They're using a Central computing module for some percentage of the vehicle features and some number of ethernet switches around the vehicle. By stating that hardware shown was the "Front Left" implies that there might be at least 4 more zonal switches, and there's strong indication that the network topography is some kind of ring configuration for redundancy. So arranging the data in a TDMA also implies some kind of data muxing from the CCM. To visualize it, the CCM has multiple ECUs that will each load their data payload into a train car, which will send out onto the ethernet when the train is full. I'm not sure how the bidirectionality of the network works and I think the train track analogy falls flat when talking about that. In TDMA, the CCM should send a synchronization bit stream to all other transmitters so the data transfer is synchronous and collisions are avoided. TDMA is commonly seen in T1 data lines and GSM cell communications.

I'm hoping Tesla releases some kind of whitepaper on their network because it would be an interesting read.

 

[CyberGus]

Maybe they are using Tolkien-Ring networking ?‍

I gave you a "lol" reaction, but only because there's no button for "eyeroll"

 

[TruckElectric]

@13:25 Sandy mentions "communication over power" guessing he is referring to PoE and Pete Bannon says "no" they use 2 more conductors then explains they have gigabit ethernet, bi-directional for redundancy.

@19:30 Pete Bannon explains the ethernet comms.....says it "looks like a token ring network" then David Lau explains it's a TDMA(Time Division Multiple Access) network.

@39:15 Sandy and Pete look at the 48V "left controller" Pete points out an ethernet loop connection says it's standard twisted-pair shielded cable.

Also when Ganesh Venkataramanan left Pete Bannon took over the Dojo supercomputer project.

Starting at 18:53 David Lau mentions "a small number of basically ethernet routers"

Wonder what these routers look like?

 

[Dazureus]

Starting at 18:53 David Lau mentions "a small number of basically ethernet routers"

Wonder what these routers look like?

I believe the routers he's referring to are the zonal switches, which was the first board that was displayed. Those should be the only devices besides the CCM that's connected to the ethernet loop. The zonal switches then translate the TDMA data relevant to it's zone to CAN protocol for the local devices connected to it.

 

[TruckElectric]

I believe the routers he's referring to are the zonal switches, which was the first board that was displayed. Those should be the only devices besides the CCM that's connected to the ethernet loop. The zonal switches then translate the TDMA data relevant to it's zone to CAN protocol for the local devices connected to it.

You may be very well correct. Only thing is I would think David Lau knows the difference between a router and a switch......

 

[Dazureus]

You may be very well correct. Only thing is I would think David Lau knows the difference between a router and a switch......

Yeah, but I don't think his audience (Sandy) knows the differences. Maybe since they're talking about the router communicating to other devices via CAN, router could be a more appropriate description since a router sends information to multiple devices and a switch sends information to devices based on the MAC addresses of the packets. Since their "routers" aren't sending to smart actuators based on MAC address, as it would in a full zonal ethernet architecture, router might be technically more appropriate.

 

[TruckElectric]

Yeah, but I don't think his audience (Sandy) knows the differences. Maybe since they're talking about the router communicating to other devices via CAN, router could be a more appropriate description since a router sends information to multiple devices and a switch sends information to devices based on the MAC addresses of the packets. Since their "routers" aren't sending to smart actuators based on MAC address, as it would in a full zonal ethernet architecture, router might be technically more appropriate.

Have any idea of the size of these routers? Pics?

 

[Deleted member 17810]

oops

 

[Dazureus]

Have any idea of the size of these routers? Pics?

I don't think we'll get specific details about the comm architecture until a tear down or more techical discussion with the engineers. The Munro video you cited is the first glimpse at any comm hardware so far. All other information has been pieced together from tidbits thrown out there, along with automotive industry standards for vehicle ethernet communications.

 

[TruckElectric]

I don't think we'll get specific details about the comm architecture until a tear down or more techical discussion with the engineers

But no idea of anything comparable? So many have been doing it already......

A wiring diagram of the Cybertruck would take a WikiLeaks-type operation.

The Munro video you cited is the first glimpse at any comm hardware so far.

I figured that.

All other information has been pieced together from tidbits thrown out there, along with automotive industry standards for vehicle ethernet communications.

And not all of it has been correct.

 

[Dazureus]

But no idea of anything comparable? So many have been doing it already......

A wiring diagram of the Cybertruck would take a WikiLeaks-type operation.



I figured that.




And not all of it has been correct.

There aren't any production vehicles using gigabit ethernet communications from a primary CCM yet. Some have implemented diagnostics over ethernet and a few are moving towards consolidating ECU's, but Tesla is the first to replace the traditional CAN bus and gateway module architecture. The Parts catalog has been released, so we get our first glimpse at the communication parts. Linked page shows three primary routers:

It also lists a few other controllers like the doors and trailer controller, but that's it. Harnesses for those three devices is labeled "Bed and backbone" harness. Interestingly, the Mid voltage battery is shown as the 48V battery. CCM is probably the "Car Computer".

 

[TruckElectric]

There aren't any production vehicles using gigabit ethernet communications from a primary CCM yet. Some have implemented diagnostics over ethernet and a few are moving towards consolidating ECU's, but Tesla is the first to replace the traditional CAN bus and gateway module architecture. The Parts catalog has been released, so we get our first glimpse at the communication parts. Linked page shows three primary routers:

It also lists a few other controllers like the doors and trailer controller, but that's it. Harnesses for those three devices is labeled "Bed and backbone" harness. Interestingly, the Mid voltage battery is shown as the 48V battery. CCM is probably the "Car Computer".

I missed the post w/parts catalog while paying attention to this thread......

Yes, 48V battery is interesting. Tesla with Cybertruck leading the way forward faster than what would have been accomplished by legacy auto manufacturers.

 

[Dazureus]

I missed the post w/parts catalog while paying attention to this thread......

Yes, 48V battery is interesting. Tesla with Cybertruck leading the way forward faster than what would have been accomplished by legacy auto manufacturers.

Yeah, it's good to know that there's a separate battery for the 48V system. In case of a HV battery failure, you'll still have steering controls under power. Hopefully there will also be some kind of short term redundant power in the steering system should the 48V battery experience failure as well. At least enough power to steer to the side of the road.

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