Yet car manufacturers don't do this. CAN transceivers are still too expensive to build into every bulb. Instead, a single CAN transceiver and microcontroller will control a whole set of nearby bulbs (eg. brake, indicator, reversing lights). That then makes it vehicle specific, so you don't get the economies of scale of just making a single model of can-bulb which fits lots of places in many cars from many manufacturers.

No, that's not obvious at all.

Separating the control board and the bulb is obvious. You wouldn't want to replace your entire control circuit every time you need to replace a bulb, would you? You don't want to have to reprogram your ECU to know which bulb serial number corresponds to your front headlight.

> That then makes it vehicle specific, so you don't get the economies of scale of just making a single model of can-bulb which fits lots of places in many cars from many manufacturers.

Car companies make millions or tens of millions of cars per year.

When you're making 10s of millions of something every year (or 2X that for parts that come in pairs, like headlights), you already have economies of scale.

Automotive equipment manufacturers will also share components between car companies, and further upstream you have companies that make chips for auto makers who share chips across the companies.

Automotive manufacturing is a great example of economies of scale. It's not correct to say that auto manufacturers aren't leveraging economies of scale while producing 10s of millions of common parts per year.

It's really not a sustainable approach to try to address nodes on a CAN bus by serial number, though. CAN is content addressed rather than receiver addressed. Due to the way arbitration works on the bus, it's invalid for two nodes to transmit to the same CAN identifier. The arbitration mechanism breaks down and results in error frames, at which point the CAN bus is in a degraded state.

That would preclude a CAN enabled bulb from being able to send telemetry back, at least until the bulb was provisioned an identifier. That could be done by an ECU sending a frame with the bulb's serial number and assigned identifier. You still need a zero-conf discovery protocol, though, and so you're back to transmitting before provisioning. You could work around all that, but it's a lot of work.

Stepping back a bit, running a car's CAN bus over a light bulb socket is going to cause some practical reliability problems. Compared to a wire harness going into an ECU, a user serviceable bulb socket is going to be much more prone to intermittent connections from vibration, as well as oxidation and wear. Intermittent connections on CAN_H/CAN_L tend to cause a ton of frame errors, and significantly degrade the overall bus performance often to the point of system failure. When a node encounters enough error frames, it is compelled by the standard to go into a BUS-OFF state where it isolates itself from the bus. Because it's a bus and all the nodes share the same two wires, it's pretty much impossible to diagnose where an intermittent connection is without trial and error.

Ie, with CAN, each node only needs to do reg reads/writes/datasheet-spelunking for a narrow part; the other nodes just need to know the API that sits on top of the hardware.

See for example https://github.com/commaai/opendbc

Quite old and for Wundows, but a lot of code showing how to use a lot of CAN interface boxes is at https://github.com/rbei-etas/busmaster/tree/master/Sources/B...

There's rules of thumb about never overloading a CAN bus beyond, say, 50% utilization. That's because systems with poor prioritization management tend to start falling over around there. With a well thought out scheme, it's possible to push a CAN bus fairly close to 100% utilization. I built several safety critical systems that pushed 80% utilization on average. At that level, you really need to rely on redundancy rather than simple robustness, though. A CAN bus running at 80% falls over very hard when you have a flaky physical connection somewhere.

In the factory, you fit the bulbs in a certain order every time, and the computer knows that order.

Just imagining the customer support for this is gonna give me nightmares.

“Sir, you need to make sure your vehicle’s ignition is turned to accessory mode. Then wait for the light to blink twice, that’s the vehicle’s confirmation that it correctly identified the new light. If it blinks three times, it can’t confirm the light’s location, so you should try removing it and re-inserting it. If it blinks four times, that means you didn’t replace the bulbs in the correct order so you need to initiate a manual reset procedure by going to the driver’s seat and…”

I’m guessing you’ve never worked in customer support. The failure modes of mistakes would be nasty. Even smart people swap bulbs around when diagnosing faults.

Simplicity (good usability) is most always crushingly hard to achieve, doubly so for hardware.

Calling things “simple” is often a sign of shallow thinking in my experience - something a customer or manager might naively say but an engineer cannot (because they have to deal with all of the real requirements).

For example, the engineers that build cars can’t say “you simply push a button to start a car” - as an engineer the complexity behind that simple operation is very very deep.

That sounds like a good thing to me.

(I'm not sure though - it might be some headlight controller fails non incandescent bulbs)

You make it sound as though this intended to be a benefit to the consumer or the end product. Having worked on and around cars, and being friends with people who do for a living, I am really unconvinced that the manufacturers do a lot of this for any consumer-friendly reason, rather than simply trying to squeeze a buck out of you.

I can absolutely tell you that Volvo, for example, does what the GP is talking about, and then some. On an old school GM or Toyota, if you break a simple switch or knob, or things that really should just be simple devices, you can just pull it out, go to the junkyard or a parts retailer, and put the new one in and be on your way. Not so for Volvo (and I'm sure this has caught on in other manufacturers): if your switch or control or whatever fails, and its hooked up to the CAN-bus, whatever replacement you find simply won't work until you've gone to the dealership (if they even let you use a part that didn't come from there at all) and gotten them to flash the part and whatever other crap needs flashing like a BCM to get them to be compatible (I think just flashing the serial number of a BCM or whatever it needs to play nice with to the switch), at the tune of a couple hundred or more dollars each time.

So in essence, a stupid simple part, that should have been $5-10 that the manufacturer likely never would have seen a dollar from in the aftermarket, is now a $200+ dollar flash at the dealership, using the manufacturer scan tool, and also increasingly requires only parts the manufacturer can generate. So no, I really am extremely skeptical, given what occurs *today* that 95+% of the junk on CAN bus is there for any reason other than to boost dealership and manufacturer profits for no other reason than the fact they can.

It's often the case that consumers will seek out the lowest price no matter how high the cost.

How do you say this with a straight face?

they can be expensive, but you can buy them. you may need to visit a dealer to buy them, but you can buy them.

right-to-repair exists for consumer automobiles.

there are no "right to secure CAN buses" laws, unfortunately.

Say I only need to replace a $5 switch as the parent poster suggests. My options then are pay $200 to the dealership to flash and install it (if they'll even flash a third party part) one time, or I can pay thousands of dollars for a tool I'll use once and do it myself.

That isn't a real choice, and the auto makers are adhering to the letter of the law but not the spirit of the law. Which is legal for them to do, but it doesn't make it any less scummy.

There's a reason they're called stealerships - and the service department is where all the profit is. (Well, that and used cars).

Chrysler (and probably Stellantis so Jeep, Dodge, Fiat, RAM, etc) charges $35 per VIN per year. https://kb.fcawitech.com/article/vehicle-reprogramming-subsc...

Ford I believe now requires a subscription for diagnostics but I haven't seen anything about per VIN charges yet. I'm not sure about the British or Japanese brands either. This is AFAIK regardless of dealership or independent shop.

The problem is as I always point, that people want complexity and technology for everyday but as soon as something breaks they want it to be like 1990.

The article complais about CAN bus not being secure but this sort of attack is very rare, you need special tools, skills, physical access to the network and time. Regular car thieves don’t go and make a key to steal a car, that would be the same as a 1980’s one breaking a window and start trying to decode the cylinder and then cutting a key! How does a towing company get your car in 10 seconds? That’s how they’re stolen most of the time.

the automotive parts industry is massive and if you allow third party parts manufacturers to make parts for your car, you are undercutting your own parts replacement business. how do you counter that? you require that replacement parts come from you. the only way to do that is via electronic means, because anything purely mechanical can (and is) reverse engineered quickly.

insurance companies fight against this in court because 3rd party parts are much cheaper than official parts, and usually come with an associated dip in quality as well, which is another reason auto makers fight for first-party parts businesses.

Honda doesn't want Snake Oil Autoparts stuff installed on cars which are still under warranty after a collision, for example, but the insurance company paying for those repairs definitely does.

They lost the right to require things to do with thr car the y sold the car.

Electronic lockouts will be cobsidered theft one day

not if you want a warranty or any manufacturer support on the vehicle at all, and these are things that consumers value a lot.

> Electronic lockouts will be [considered] theft one day

among the most feverish people, they are considered a problem worth fighting, which I agree with, and I don't think it will ever be considered theft. the law just doesn't support electronic lockouts as theft, and precedent on this would be very difficult to undo without changes to laws defining what ownership actually is.

(Genuinely curious; I had no idea such laws existed for cars.)

And only for regular cars, there is no right to repair for commercial vehicles: https://en.wikipedia.org/wiki/Motor_Vehicle_Owners%27_Right_...

There are also long-standing legal requirements for automakers to be separate from car dealers, which also translate into making the repair/diagnostics equipment available.

Their profit margins will come from somewhere. If not from savings then from higher pricing.

I'm working on Right to Repair and we get asked for examples like this from various government agencies all the time. It would be very helpful, thanks!

If you're looking for something a little more formal, I think the factory service manual probably calls out that the R&R on a ton of parts will involve reprogramming. I no longer own any post-Ford Volvos nor do I have any interest in European cars, so unfortunately I don't have any newer FSMs. A way you might be able to get at one on the cheap is to pick a popular model/year later Volvo (maybe like a 2016+ XC60?), and get a subscription to the make/model/year on Alldata (which was something like $20 a year for just a single combination), or hunt for an FSM on eBay, if it's old enough to still have a paper FSM.

The "consumer friendly" part is competing on price; they don't care about repair cost, in fact parts for repair is just recurring revenue on top on (till before pandemic) slim margins on selling the car

Isn't that what's supposed to happen in capitalism? Everyone working is getting paid, supply matching demand, prices reducing and ostensibly zero profit for established sectors.

It's like putting everything over IP (VoIP, video over IP, audio over IP, etc.) and then just running Ethernet throughout your building. From an engineering perspective, it's just way easier. Routing wires -- on a circuit board, in a building, in a car, in anything -- is just a real PITA.

Now it's definitely true that having to flash something on the CAN bus to make it work is possibly due to greed, but the original idea of putting things on one bus is not.

There's no way I would ever recommend someone who wanted to keep their car past the first 50 or so thousand miles ever buy a VW or a VW with slightly shinier wallpaper (Audi). There's a reason the service techs on those and BMWs get paid well, and why they're often hated by mechanics.

I bought a $20 OBD2/J2534 cable, downloaded an easily-available ["pirated"] copy of Honda HDS, and seemingly had access to all the functionality a dealer would have. From looking at the Honda website, I could have paid by the day/week/etc for official access to flashing tools or the newer iHDS, which I might have needed for a newer car.

If I had wanted to reflash any of the modules, I probably would have wanted a better cable (though, it's hard to tell if manufacturers really have such shoddy update code that interrupting flashing can brick a device, or if that's just persistent superstition, like so much in the car world). But I was able to replace the VSA/ABS module and perform the necessary "dealer reset" procedures no problem. I just wish I had obtained this setup before I went about misdiagnosing the problem based on a document that claimed to be the OEM service manual but actually wasn't. Luckily the part I misdiagnosed to did end up being the problem!

Of course, I would love for there to be some sort of mandate for manufacturers to document the details of all CAN messages. Because there don't seem to be that many different module manufacturers, they must all be working to some kind of internal standards for their own interchange, and end-user visibility into computing systems is critically necessary for preventing computational disenfranchisement where people see these systems as impenetrable black boxes. But it feels at least in Honda land, much of that capability is practically available to the repair market (at least as of 2015 model years). One just needs to get over the activation energy of setting up the OEM software tool.

I'm adding a CAN bus to my 3d printer for this exact reason.

I know this stuff "pays off" for the manufacturers, but I really wish they'd avoid including unnecessary complexity such as those horrific touch screens, call connections, etc. That sort of thing is why I won't buy newer cars.

Maybe, but given the explosion of weight and cost of new vehicles, it's unclear where these savings went.

One huge problem is that they put the smart key on the same bus as other stuff (headlights, body control) to save money/wiring.

These kinds of busses should be buried far inside the dashboard or some other hard-to-reach area.