I’m working with CAN communication in an Audi vehicle and I have a question regarding the use of 29-bit identifiers (extended CAN), since I previously worked with 11-bit CAN where, when responding to diagnostic frames, it is common to apply the logic of adding 0x08 to the ID (for example 0x7E0 → 0x7E8), which is quite straightforward; however, in this case I am analyzing frames such as ID: 0x18DAF110 and I understand that the structure is different (including priority, protocol, and addressing), but it is not clear to me how to correctly construct the response, since it seems that the 0x08 addition rule does not apply here, and instead it may involve swapping source and destination addresses or depending entirely on the protocol such as UDS over ISO 15765-2; therefore, I would like to know if there is an equivalent rule for generating the response in 29-bit CAN or if the ID must always be fully reinterpreted, and if someone could explain it with a practical example (request → response), it would help me a lot to implement it correctly in my system.
