PXI-8433/4 Shorts The RS-485 Bus

Updated Jul 22, 2021

Reported In

Hardware

  • PXI-8433/4
  • PXI-8433/2

Issue Details

We have two NI PXI-8433/4 modules in two separate chassis running on Real-Time Operating System and connected in parallel to the same RS-485 bus. There are a few sensors on that bus with RS-485 interface.
One of the PXI-8433/4 modules is writing and reading the commands to/from the sensors.
The second PXI-8433/4 module is used only for listening the RS-485 bus.
A communication issue comes up when the two PXI-8433/4 modules are connected to the same bus. Still, if one of them is being disconnected everything is operating correctly.

Solution

This issue can arise in case if only one of the PXI-8433/4 modules is not configured.
The output parameters of the non-configured module will cause shorts on the RS-485 bus. Therefore make sure that the non-configured or unused module is disconnected from the RS-485 bus.