Reverse Camera: Audi A5 Analog to CAN Conversion

Hello CANhack users,

I registered here because I have a problem with my A5 and I hope someone can help me.

Here's a brief introduction about me: My name is Eduard, I am 27 years old, and unfortunately, I don't know much about CAN bus programming.
While I've started learning things here and there, I think it's still a very long road to achieve initial success, even though I completed an IT education program about 10 years ago and have some basic programming knowledge.

Why I'm writing this:
I own an Audi A5 from 2007 that has been modified with the facelift components and engine control unit (ECU). Unfortunately, after the modification, the reverse gear signal stopped working. After some research and studying wiring diagrams, it was discovered that in the facelift models produced from 2012 onwards, the reverse gear signal is no longer processed by the transmission but by the engine control unit. In my case, however, it's still being processed by the transmission via a reverse gear switch located within the transmission. The two pins coming from this switch connect to the body control module (BCM) of the facelift model, just like they did with the original ECU, but these pins are not connected in my car.

Now, here's my thought process:
There are CAN modules that read the reverse gear signal from the CAN bus and output it as an analog signal to connect, for example, a reversing camera. I've already searched, but unfortunately, I haven't been able to find a module that does the opposite. Therefore, I need a circuit that takes the signal from the reverse gear switch as an analog input and injects it as a digital CAN bus reverse gear signal into the bus, so that the reversing light turns on, and ideally also the parking sensors (PDC).

While there is a suitable body control module from the facelift version for my A5, Audi has already discontinued it because it was only installed in pre-production models, and finding one used is more unlikely than winning the lottery. And as far as I know, there are at least two other people in the A5 forum with the same problem .

Therefore, I wanted to ask you all.

Is there anyone in this forum who would be interested and have the time to develop and build something like that? Of course, it wouldn't happen for free, and we could certainly come to an agreement.
Technically, the A5 is identical to the A4 8K in terms of its components, and the control units are also the same. However, I believe that the reversing signal should be quite similar across all VAG vehicles.

I thank you in advance for reading the novel and hope that someone feels addressed .

I hope you can help me with this.

Hi,

If the reverse signal is on a CAN ID that is not yet being used, then the hardware is already complete. It needs to be clarified what data is being sent on the bus when in "reverse gear."
It becomes more complicated (as no ready-made hardware is available) when the reverse gear status is transmitted using a CAN ID that is already in use, because this requires two CAN transceivers between which the corresponding message must be exchanged and manipulated for the reverse gear function.

Best regards, Rainer.

Currently, my Audi doesn't realize it's reversing because the reverse gear switch in the transmission is mechanically activated by the transmission, but both cables essentially lead to nothing, as the pins are no longer connected on the new onboard computer system.

I saw in another thread here that there's a user who supposedly has the ID for the reversing signal for the A5.

How should I proceed best?
Do you already have the right hardware ready for Rainer?

I was considering buying the sniffer, but I don't think I'll be able to build something like that myself. Instead, I would rather pay someone else that amount of money as a 'thank you.'
I have also already contacted two companies, but both told me that the effort for one person is not worthwhile.

I would prefer to find a more professional solution before resorting to simply wiring a basic relay directly to the taillight as a temporary fix, just so that at least the reverse light illuminates when driving in reverse.

Thank you very much.
Have a nice weekend!
Eduard.

As I mentioned, the difficulty lies in determining where (the CAN ID and message structure) the information for reverse gear is expected.
Knowing this, there are two ways to proceed: a simple one (using an unused additional ID = hardware ready) and a more complex one (incorporating the information into an existing CAN ID, specifically adding the "reverse gear" information).

Best regards, Rainer.

Is there a solution to this yet?

Please provide some specific details about the vehicle, including the engine code and transmission code.

Then I might be able to help you further.

Best regards,

Hello,

Unfortunately, there's nothing new on that front.

Engine code is CAPA (3.0 TDI Quattro).
I need to check the gearbox code, but it might take another week because it's currently at the paint shop. However, it is a manual transmission.

It would be great if you could help!

Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

Then please tell me the gear identification letter if you can.