Help keeping a CAN bus alive using a NI 8516 CAN interface.

[Eduardo_230]

Good day

I am having some trouble  with our HiL test system.  We have a PXI controller with ECU simulations injecting CAN messages via a NI 8516 CAN interface, as well as real ECU injecting messages into the same bus.

Everything works fine when  real modules and simulation are in the system, but when real modules are disconnected from system the bus dies, and all communication stops, even though simulation should continue to inject messages.

I have tried connecting a 120 ohms resistance between High and low cables, also wiring V- and V+ using the following pin-out diagram. Normally we just connect CAN+ and CAN- and works fine, but now that we need to take the hardware modules and just let the simulation its starting to fail.

Any advice to keep alive the bus? Do you think I am failing in wiring, or maybe  some software config? I  cant see in NI Max a way to configure this CAN interfaces. I also tried connecting just a Vector CAN case in order to keep alive the bus and works as fine as the hardware ECUs.

[JB]

According to the CAN protocol, a message must be acknowledged by a receiver.

Since the PXI-8516 has two ports, connect the second to the bus and use it to ensure the acknowledgement when no ECU is connected.

As a first trial, I would use the bus monitor (available in MAX) with the "Listen only" option disabled.