NI VISA Driver for Mac OS 10.15 (Catalina)

This post is of interest if you run the VISA XOP on Macintosh.

VISA (Virtual Instrument Software Architecture) is a system that provides instrument control via serial ports, GPIB, Ethernet, USBTMC and other media.

Igor's VISA XOP relies on a VISA library. Most people use the National Instruments library named NI-VISA.

National Instruments recently released version 20.0.0 of the NI-VISA for Macintosh. This is the first version that supports Mac OS 10.15 (Catalina).

I successfully installed and tested NI-VISA 20.0.0 on Mac OS 10.15 (Catalina) and Mac OS 11.0 (Big Sur) beta 4. However, installing the library required jumping through hoops. The following describes what I did. Your experience may be different.

1. Download the latest NI-VISA library for Macintosh.
   As of this writing, this produces a file named NI-VISA_Full_20.0.0.pkg.
2. Double-click NI-VISA_Full_20.0.0.pkg.
   Mac OS displays a dialog saying "NI-VISA_Full_20.0.0.pkg can’t be opened because Apple cannot check it for malicious software".
3. Click OK.
4. Open System Preferences, enter the Security & Privacy section, and click the General tab.
   It says "NI-VISA_Full_2.0.0.pkg" was blocked from use because it is not from a identified developer".
5. Click Open Anyway.
   NI-VISA_Full_20.0.0.pkg runs again. Again, Mac OS says "NI-VISA_Full_20.0.0.pkg can’t be opened because Apple cannot check it for malicious software".
6. Click the Open button and proceed with the installer as usual finally clicking Install.
   The installer goes about 90% through the installation process. Then a dialog appears saying "System Extension Blocked - A program tried to load new system extension(s) signed by “National Instruments. If you want to enable these extensions, open Security & Privacy System Preferences."
7. Open System Preferences, enter the Security & Privacy section, and click the General tab.
   It says "System software from developer National Instruments was blocked from loading".
8. Unlock the dialog by clicking the lock icon and entering your password.
9. Click Allow.
   A dialog appears saying "Legacy System Extension - Existing software on your system loaded a system extension signed by National Instruments which will be incompatible with a future version of macOS. Contact the developer for support."
10. Click OK.
    The NI-VISA installer says "Registering updated components" and shows no progress for a minute or two. Then the NI-VISA installation completes.
11. Restart the machine.
    When I restarted the machine, the restart failed and the machine displayed a circle with a bar through it. I then pressed the startup button for six seconds causing the machine to shut down. I then restarted while pressing the option key and selected my boot drive, and the machine started successfully. I then successfully tested the VISA XOP using a USB-to-Serial adapter.