PEAK-System Forum

Hello,
I am a little stuck on my project. The situation is following:
- I have a CAN network with two nodes UUT and PCAN-USB
- UUT is sending periodically some messages, which are not interesting for me BUT
- just at the moment I call UDS_Initialize(), the PCAN-USB starts to send responses which I didn't configure
- this response follows around 1ms after MSG with ID 0x1BFF8304 (from UUT) and just only when the first data byte is between 0x0F and 0x1F
- CAN-ID of this strange response is 0x1BD827F0
- the same behavior occurs, when UUT is replaced by another USB-CAN converter

What should I do to make PCAN-USB stop responding? Did I forget to configure something?

Radek

Hello,

In fact some 29-bit CAN ID messages can be automatically interpreted as ISO-TP frames, in your case the API detects that the frame can be a ISO 15765-3 messages: the CAN ID matches the format of "Enhanced diagnostics 29 bit CAN identifies".

0x1BD827F0 in binary is:
0001 1011 1101 1000 0010 0111 1111 0000
Black, bit [28..26]: Priority
Red, bit [25..22]: ISO 15765 format and type of service ISO 15765-3 messages
Blue, bit [21..11]: Source address
Green, bit [10..0]: Destination address

Depending on the first data byte of your message, it will be detected as a Single Frame or First Frame. If it is a First Frame, the API will send a Flow Control frame (stating that the other can transmit the segmented message). This is an automatic mechanism by the ISO-TP API which is used by the UDS API.

Since your UUT does not really send an ISO-TP message, the ISO-TP message will fail and be discarded by the UDS API. Let us know if it is a major problem and if you think a parameter should be added to disable "Enhanced diagnostic messages" in ISO-TP.