Toyota's firmware: Bad design and its consequences

Re:Toyota's firmware: Bad design and its consequences by fnordfnordfnord on Tuesday October 29, 2013 @05:10PM (#6637455)

Mfrs have started using LIN for slow-control accessories like power windows, door locks, wipers, etc. A separate CAN for critical functions of the auto, and another (sometimes CAN) system for non-critical things like GPS integration, entertainment, and (apparently) MOSTbus has finally taken off after much teeth gnashing. MOST is a higher bandwidth than CAN bus system designed for 'infotainment' systems in autos. https://en.wikipedia.org/wiki/MOST_Bus

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Re:Toyota's firmware: Bad design and its consequences by drbawb on Tuesday October 29, 2013 @05:37PM (#6637659)

Thanks for sharing!

I have to admit though I'm surprised that some of those accessories even require a bus as they're typically operated by simple switches.

I guess door locks, wipers, etc. make some sense: with the prevalence of central locking, as well as wipers that sense rain and things like that.

Windows are a bit odd, as they just need a very simple switch. I suppose having all the accessories on a common bus must simplify the wiring harness though.

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I'm curious how TESLA integrates their in-dash system with the rest of the car.

I thought their in-dash console could control some rather safety-critical "preferences" of the car ... for instance I thought you could adjust the level of regenerative braking.

(Other manufacturers are also offering "sport modes", etc -- though they're not always controllable through the dash.)

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Re:Toyota's firmware: Bad design and its consequences by fnordfnordfnord on Tuesday October 29, 2013 @06:11PM (#6637865)

>I have to admit though I'm surprised that some of those accessories even require a bus as they're typically operated by simple switches.

They certainly don't require a bus in principle. However, if you want to understand both the business case and some very good engineering reasoning behind the use of data buses to control simple automobile accessories you should have a look at the wiring harness for an early 90's Mercedes or similar luxury car. Demand for fancy features drove the number of wires running to and fro to an unmanageable level. Having a mile of wires in a car is expensive for many reasons I'm sure you can imagine, as well as each connection point becoming an opportunity for something to go wrong.

I'm also curious how electric cars in general will manage safety systems going forward, especially in light of this Toyota court decision.

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Re:Toyota's firmware: Bad design and its consequences by lsaferite on Wednesday October 30, 2013 @12:10PM (#6641232)

One example of where a CAN/LIN bus connected power window is good is my old Jetta. You could insert the key in the driver door lock and turn it backwards to make the car roll down all of the windows and open the sun roof. As someone else mentioned, you can likely implement features like this via hard wiring, bu then you get massive wiring harnesses.

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