Chance to Succeed: What Are Your Odds?

hi

My 'goal' would be the following:
When locking the door on an Astra J, the windows should automatically close.
and a few other functions that are based on an 'if this, then do that (or don't do that)' principle.
Ideally, program an Arduino with a CAN adapter that is connected to the OBD port.

Here's what I know:

- Programming Arduinos (though I have no experience with CAN).
- Theoretical knowledge of how CAN (Controller Area Network) functions.
- Electrical knowledge (trained electrician)
- Basic knowledge of Opel systems, including the three bus systems: Low Speed, Mid Speed, and High Speed, and which ECUs (Electronic Control Units) are connected to each. I don't know the specific IDs or other details.
- Good understanding of technical concepts and logical thinking; I grasp such things relatively quickly.
- very good at searching on Google

What I'm missing:
- Practical experience with CAN (Controller Area Network) technology.
- How I should best approach this.

What do you think, is something like that even feasible, or would I inevitably fail because the effort required to write on the bus is too high?

My thought is:
I'm monitoring the bus signals, pressing a button, and then hoping to see what was just sent in the message logs. I then send that same data using my controller to the bus, hoping that this function will also be executed.
So, as a practical example:
My 'logger' is connected and reading data. When I press the 'close window' button, it logs the information about closing the window. The same applies to locking the car; then, a simple 'if-then' program runs on the Arduino, and that's it.

Am I oversimplifying this, or should it be possible to do it this way?

Best regards,

What's so difficult about it? All the data is accessible; it just requires perseverance.

It took me six months to complete a similar project – because I relied on a supposedly widespread and well-tested CAN library. Turns out, it was all wrong! In the end, I had to write the entire CAN interface myself. If I had done that from the beginning, I would have saved a lot of time (and even more nerves).

When choosing hardware, be clear about your system requirements. In my case, a CAN controller connected via I²C was 'slightly' undersized. Personally, I wouldn't even consider using an Arduino - although I don't know your CAN baud rate or bus utilization. But for me, with 500 kBit/s and the corresponding high data volume on the drive-side CAN bus, it would be undersized.

candev

hi

Thank you for the answer. Maybe I'll actually get around to it .

If I understand correctly, I shouldn't actually need to connect to the 500kbit/sec motor bus? For Opel, wouldn't all the signals I'm looking for be available on the Low Speed Single Wire? The signals I'm trying to obtain should come from the BCM (Body Control Module), and according to my information, the BCM is connected to the Low Speed Single Wire.

This one has a data rate of 33.3 kbit/sec, while the I2C bus on the Arduino runs at 100 kbit/sec. Therefore, the data rate should be sufficient for now.

I can't really estimate what the processing power is like.

Here's the translation:

'Furthermore, what kind of shielding is suitable for a single-wire bus? It's probably not as straightforward as with a standard CAN bus, right?'

Best regards,