Solution
Installing Software and Detecting Hardware
- Make sure that the installed version of NI-VISA is the same on both the host PC and cRIO (Real-Time (RT) target), using the Software tab under both the cRIO and My System.
- If the wrong version is installed on the development system, you can download NI-VISA from here.
- If you need to change the version on the CompactRIO, follow this guide to install the correct version.
- Make sure the NI-Serial 9870 and 9871 Scan Engine Support is installed on the RT target.

- Finally, if none of the previous steps worked, you can also try to reformat the CompactRIO disk and reinstall the software. You can try to upgrade or downgrade the firmware of your CompactRIO regarding the version of the NI-VISA driver you have installed on your device.
After installing the right software, you should be able to see the COM ports for your module in different locations depending on the cRIO OS. Please refer to Real-Time Controllers and Real-Time Operating System Compatibility to find out what operating system your cRIO controller is running.
NI Linux RT target
For NI Linux RT targets, the serial ports appear under Devices and Interfaces but not under the NI 987x module.

Phar Lap ETS or VxWorks target
For Pharlap ETS or VxWorks target, the serial ports appear under the NI 987x module.