Eliminate a wasted J1939 CAN BUS

Forrest 4 years ago updated by Gustav Widén (System support) 10 months ago 2

I run a dedicated J1939 Bus to speak with the Vehicle CAN. I imagine most do it this way.

Now that I have to cover for the possibility of both 250kbs and 500kbs J1939 vehicle CAN buses, and do not want to have multiple versions of software floating around if I can help it (tried it, can be a bit of an unneeded mess), I am running out of CAN Buses on my MD3s.

The way it is now, I am planning on setting up 2 vehicle can buses, each with their own "engine", then pick which engine to enable in the settings (250kbs, 500kbs, or disabled). Unfortunately, that leaves me with a wasted Bus since I can not run both the 250 and the 500 to on the same physical CAN Bus pins. An empty Bus might even throw an error. I haven't tested it yet.

It would be nice to be able to select J1939 bus speed in the software settings or be able to disable the unused bus in the settings. Either would free up a bus on the MD3 so I wouldn't have to put absolutely everything else (Master, Expansion, Diagnostic, and J1939 components) all on the same physical bus.


IQANdesign 5 will let you control J1939 bus speed with a new concept we call constant channels. These are normal channels that are calculated once at startup and then have the same value until shutdown. The integer parameter channel (IP) will be available as a constant channel for example. IQANdesign 5 is planned for release this summer.


This is how to use a parameter for the J1939 baudrate: