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Comment by Zemtomo | Hacker News Reader

Just to be clear: you build an engine controller with a normal arm cortex-m0?

And if this thing breaks the engine just do nothing?

Did you build any hardening or redundancy into it?

If the ignition unit dies, the car will just turn off. I did add the power supply hardening, am using automotive rated components, and I'm actually able to ignore one of the three engine speed/TDC sensors in the car upon failure and still run, but other than that no redundancy. The original boxes do not have any redundancy either, so I'm still providing a "like OEM" solution.

I know at least one Ford ECU (1996 Ford Escort ZETEC) which has a limp-mode backup controller if the main ECU processor dies, so no, at least some ECUs have redundancies inside.

Oh, I'm sure a lot of engine ECUs have redundancies, probably most at this point. I was speaking toward the Magnetti Marelli Digiplex ECUs from the 1980's specifically. They have no redundancy.

Cool to read about this.

I'm in Munich close to Bmw etc and whenever I did something with automotive it would say 'automotive grade components '.

I would not have assumed this would just work.

Is this also connected to can? Or is this only for old cars? So what inputs does it use?

It is only for direct replacement of the OEM ignition units on these Ferraris. The cars pre-date any kind of diagnostic bus. Although some cars of the era did have at least some flash code based diagnostics, the Ferraris really had nothing until the 348 came out in 1989.

Why would it need hardening or redundancy?

The original system hasn't got any.

I definitely gave hardening and redundancy some thought when designing. Just because the originals didn't have it doesn't mean it wouldn't be a nice thing to add. So I think it's a fair question to ask. But I decided it was mostly impractical for my design goals and price point.

My experience with cars is not very deep but I did hear a lot about redundancy, isolated systems, real time requirements and automotive grade components.

Also I would say that controlling the ignition is very critical to a car.

Those are all important, but modern improvements. In the 1980's electronic management of engine systems was still very new to the scene and so most of the systems are still pretty basic.

> Also I would say that controlling the ignition is very critical to a car.

Indeed.

Yeah, there's none of that in car ECUs.

If something happens to the system that controls the ignition, it either runs poorly or stops altogether. No biggie.

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