Intercepting signals via CAN or OBD2

Hi,

I want to install additional instruments in my car. However, I don't want to run any extra wiring, as the data is available via CAN (oil temperature, tachometer, etc.). What's the best way to tap into the signals? Unfortunately, I don't have any ideas at the moment. Theoretically, I could use a CAN adapter (which probably involves building one myself) or the OBD2 interface (which seems like the easier option). Can anyone give me some advice?

Using KWP (also OBD) is a less reliable method, as it puts a higher load on the ECU, which can lead to failures in safety-critical systems.

use 'can'

You can pause whenever you like, or however it's easiest for you.

Safety-critical functions will not be compromised in any way by the load, so it doesn't matter whether you use OBD2 or CAN. Furthermore, even the manufacturers of the ECUs have recognized that safety-critical functions should be prioritized over functions like diagnostics.

Oh yes, and to debunk another common myth,
Even the engine will not shut down due to load on the diagnostic interface (provided you are not dealing with a DEV-ECU - greetings to all the developers and application engineers who had to find out that even very short DAQ lists can be too long.

Regards,
Jens.

Hello,

Since the bus load is lower with CAN compared to OBD, I will probably start working with CAN. I envisioned the process as follows:
Buy a CAN sniffer to capture IDs, purchase an ATMEL controller, program it, connect signals to an AD converter, and then to the auxiliary instruments.
Has anyone had any experience with that?

Okay, aside from the fact that I don't output them to analog displays, but the ATmega is perfectly suited for that.

Hi,
Thank you for the answers.
Regarding the Can-USB adapter and software: are there any free schematics available, as well as free software for sniffing and sending messages? It appears that fuchs30 is currently experiencing supply chain issues.

If you're confident in using an ATML interface to read values for display purposes, then a 'sniffer' is actually simpler.

Hi rathma,
That's exactly my plan, but I also wanted to purchase the CAN-Bus adapter from Fuchs so I can analyze the IDs.
The question was/is: Does other (free) software or circuit diagrams (for an adapter) exist?