I finally got a new layout ready and the communication "API" defined.
I was aiming for a structure with an ID, Value and checksum in binary format but for now, and to make debugging easier I made a simple API with all ASCII values: <ID>,<space>,<float><\n>.
This way I can enter a serial console and set the values manually and check if everything is working ok.
Now I have to get the STM32 code to send the values accordingly to this API.
P.S. I haven't been able to do it yet but I'm going to test the OBD comunication above the 90Km/h mark with the VAGCOM software running on the PC. If it works than it's something buggy on the code, if not than I might have to rethink this whole thing...