2 masters with the same ID tag

Viktor Kajml 2 years ago in IQANdesign updated by Damian Frankiewicz 2 years ago 2

Is the following setup possible:
MC41 #1 with ID tag 0 connected on CAN A a to a J1939 bus
MC41 #2 also with ID tag 0 connected on CAN A a to the same J1939 bus

The MC41 would not use the 1939 bus to talk to each other but to our own ECU. From what I know I think this should be possible because I can specify a different J1939 address for each MC41.

Will this work or will I get errors because both MC41 have the same tag even though they are not communicating with each other?

The motivation behind this is that we would prefer if we can simply use a single type of ID tag in production.


I think that you would need to have two programs and load the programs separately (and not through the same diagnostic bus from one to another) as the ID tag determines the program that will be loaded.

You could use the same project file and control the J1939 source address via a constant channel. 

But as Michael wrote, problems arise when sending software to the modules over CAN. 

When you connect with IQANrun connects over a CAN bus with multiple IQAN masters, IQANun has to select the module to connect to. If two master modules of the same type have the same IdTag, IQANrun will be unable to connect on this shared bus.

-On a bus where IQAN masters have different IdTags and there is exactly one with IdTag 0, IQANrun connects to address 0. 

-On a bus where there are IQAN masters with different IdTags but no address 0, IQANrun presents a selection list with all modules.

-When there are multiple master modules of the same type and with the same IdTag, IQANrun is unable to connect. It will present a Communication notification.

Multiple modules with the same address were detected on the bus. In order to communicate with these modules they need to have different addresses!

As the MC41 has two CAN buses, one idea is for you to load software through the other bus. But then you will instead need more than one diagnostic connector. 

If that bus is already occupied with other traffic that is not compatible, another option is to only power up one module at the time, so that IQANrun only sees one IQAN master with this address in the stage when you send SW to it.