Analyzing CAN messages in an Audi A5 using a microcontroller

Hello everyone,

Brief introduction:
I am 34 years old and a certified state-approved professional. Microelectronics technician, hardware development for avionics/automotive.

My personal problem:
I want to remove the digital signal processor (DSP) from my Audi A5's sound system. It's activated via the CAN bus. To use this power-on signal for my new sound system, I need to read and process the message with a microprocessor, identifying it by a specific ID.

Is there existing hardware/software for that? Can someone help me with this project?

Thank you & best regards.
Ricky.

Hello Ricky,

I could probably help you with that. I have ready-made interfaces that allow me to output a Class 15 signal. It would be best if you could send me your email address as a private message.

Is this just outputting the Kl.15 status, or are parts of the original system also being simulated?

And how is the audio connection handled in your new system?
Does the A5 use MOST for its communication?

Best regards, Andi.

Hello everyone,

I would also be interested in something like that.
I need to trigger a camera activation analogously when the CAN message indicates "reverse gear" and simultaneously detects "trailer present."

Can someone please provide instructions here on how I can build it myself?
For a semi-finished solution with self-configurability, I would need to spend 79 EUR and then another 199 EUR for the software to configure the interface, which I actually wasn't planning on doing, but perhaps there's another way with your expert knowledge.

Why don't you simply check which CAN IDs change when you put the car in reverse?

Quote:

I wouldn't really do that, although it might be possible with your expert knowledge.

That definitely isn't to give free car builds to people who just want to watch. If you find the offered solution too expensive, then simply check yourself to see what changes.

This forum is intended for people to create and post their own solutions, rather than complaining that they cannot afford a ready-made solution.

Hello everyone,

I'm not at all interested in "hooking up."
I'm going to do it either way.

I already know how to access the CAN messages that need to be evaluated. Although I don't have the exact values yet (and you don't need to tell me those, as I will definitely be able to obtain them). For the found solution using the commercial CAN interface, I first need to figure out how to configure it.

reieg99 wrote: "He built his own interfaces that allow him to listen to the bus after the ignition signal (Klemme 15) is received."
That must be a small microcontroller circuit, using assembly or C, similar to what's used with Arduino or Raspberry Pi, or something else.

That's what I was talking about. I would be incredibly interested in learning how to build and code an interface myself.

The pre-built solution will definitely work; I need to configure both signals separately to specify which ones should be listened to, and each signal will activate one of the pre-defined outputs. If both states are present (or both outputs are high), then a small additional circuit (a purely electronic matter) will raise the actual output to 12 volts, and I can then use that to control whatever I want.

I would actually find a DIY solution much, much cooler, because then I could finally get to grips with the corresponding hardware. I would probably spend even more money on it than on a ready-made solution, because I could use it for all sorts of different purposes, as it's a step in the direction I actually want to go, in the style of: "I build my own control units for my gaming setups."

"For this project, I need some guidance and a working example of how to design and program a circuit to achieve a specific functionality, such as setting an analog output to 12V based on a CAN signal received on terminal 15, as illustrated in the example."

I'm not really concerned about the coal in this context.

Anyone can take ready-made items off the shelf.
I want to build the interface myself (well, "myself" in quotes). With a lot of help, probably...
Programming it myself... (Then I won't need as much help.) That's my daily bread and butter.
I want to understand everything about it.

Above all, I want to delve into the hardware aspects, as I've never had anything to do with them before. It's completely new to me.

That's what I'm talking about.
Since there are many different ways to approach this, it's extremely helpful to get a sense of direction by looking at a working example, to understand the best way to proceed or what the optimal approach would be.

Just like https://www.canhack.de/en/viewtopic.php?t=2191 already described in the thread. But this time with a working example, "terminal 15," that I can disassemble and adapt. It's much more fun that way. Unfortunately, I'm not a fan of those academic "Hello World" exercises.

Quote:

Anyone can take things off the shelf. I want to build the interface myself (well, "myself" in quotes). With a lot of help, probably...

Also, the question is when you might want to or be able to get further training/education, and I'm already seeing that without existing hardware knowledge, it will likely take months.

A promising approach to achieving results within an acceptable timeframe, starting from scratch, would be to use an Arduino or a similar microcontroller board. If you do this as a full-time job, like I do, and you're working with a single unit, the research required to find suitable mechanical parts, connectors, suppliers, and availability, etc., can take a significant amount of time (probably more than the relatively simple circuit itself).

I assume you don't actually want to learn how to use software like Eagle, create schematics and layouts, have prototype boards manufactured, then fix errors and have the final board manufactured... the solution you mentioned would probably be much cheaper and would save a lot of time.

Best regards, Rainer.