Why Can’t I Connect to my NI PXI Chassis Modules?

Why Can’t I Connect to my NI PXI Chassis Modules?

Recently I worked on a project that involved a PXI chassis. I ran into an issue--my PXI chassis module was plugged in and properly connected to my PC, but I couldn’t see it in NI MAX, even after verifying my drivers and restarting my PC.

The solution I discovered is very quick but a bit unintuitive, so I wanted to pass along that information here. This blog will be short and sweet.

NI MAX LabVIEW PXI Chassis Modules

NI MAX could see my MXI Connection but could not recognize the chassis or its modules.



If your PC is unable to see your modules associated with your PXI chassis, try shutting down and then repowering your PC while your NI Chassis is connected and powered on with its associated modules connected. It is important to note that you must Shut Down your PC, rather than just restarting, for reasons I explain below.

If you shut down and repower your PC while the PXI Chassis is powered-on and connected, and you are still unable to see some or all of your chassis modules, try repowering it again with just one module connected at a time. You should be able to do this for all of your modules one by one until NI-MAX can see all of the modules within your PXI Chassis.

max labview pxi chassis

Success! Shutting down my PC allowed me to see my PXI Chassis and Modules


Why do I need to shut my PC down (instead of just restarting)?

PXI chassis modules connect to PCs by writing an enumeration value into the System BIOs of your PC. National Instruments has a great blog to explain how this process works and how you can ensure your PC has the Bus Resources required to store your PXI module enumeration values:

The practical impact of this process is that your PXI chassis modules will be invisible to your PC until you power on your PC from a shut down state while the modules are connected. System BIOS are not modified during a PC restart, so simply restarting your PC will not affect your PC’s ability to recognize a PXI Chassis Module.

It is possible that during a PC startup, your PC may view some of your PXI chassis modules but not all. If this is the case, it may help to power on your PC with just one PXI module connected at a time. Most PC’s retain their System BIOS values between shutdowns, so you can iteratively write each module’s enumeration value to your PC’s BIOS until all are visible to your PC and can be viewed in NI-MAX. Some industrial PC’s do not retain this enumeration portion of their system BIOS between shutdowns. For these PC’s, you will need to ensure your PXI chassis is powered on and connected with all of its modules every time your PC starts up.

This System BIOS behavior applies no matter how your PXI Chassis is connected to your PC (MXI cable directly, MXI cable to express card, etc.).


Bonus--Automatically Power on your Chassis using your PC

With one industrial PC that I used, I found that even after I had successfully connected to my PXI chassis and its associated I/O modules, I still lost connection to them every time I powered off my machine.

My machine worked by powering on my PC and then, slightly after, turning on my PXI chassis. By the time my PXI chassis had turned on, it had already missed the opportunity to write to my PC’s system BIOS. The industrial PC that I used did not retain the chassis modules’ enumeration values after a shut down, so I would lose connection to the modules every time I turned my machine off and on.

The only solution I could perform was to leave my machine and PXI chassis powered on while manually shutting down and repowering my PC. Only then, after my PC had booted up with the PXI chassis powered on and connected to it, could I see my PXI modules using NI-MAX. The problem with this solution was that shutting down and repowering my PC every time I turned my machine off and on was a tedious and time consuming process, and it left room for confusion from new operators.

Luckily, NI has an executable that can trigger your PXI chassis to automatically turn on whenever a PC that is connected to it through an MXI cable turns on. This will trigger works before your PC accesses its system BIOS, so that every time you shut down and repower your PC, the PXI chassis can write the appropriate enumeration values anew.

You can find the executable to configure your PXI chassis here:

Once I used this executable, my PXI chassis turned on at the same time as my PC, and I was able to power on my machine and immediately achieve connection between my PC and the PXI modules.



Although shutting down your PC is a very quick debugging step to address your PXI modules’ connection issues, many PXI users may not be aware of the PXI module to PC connection process, and thus will not know to try this troubleshooting step. Hopefully this blog saves you some time, and helps you along the way to a successful project using the NI PXI chassis!


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