Disabling USB on PXI controllers

[AnthonV]

It has been suggested that USB should be disabled in the BIOS to reduce jitter in a RT application running on a PC (like the PXI controllers).  

My question is:  on a system (like the PXI-8108) that does not have a PS/2 connector, will disabling the USB not prevent the use of a keyboard or mouse so that it may be impossible to enter the BIOS setup again, or is the USB always active while the BIOS executes during booting? 

[Ali M]

Hello,

As described in the KnowledgeBase included below, you can disable USB support by changing the real-time initialization file.  This can be done by adding a token to the NI-RT.ini file which is located on the RT target. You can access it via ftp://targetIPaddress/. In the [SystemSettings] section of /ni-rt.ini, set EnableUSB=FALSE save the file and reboot the system. 

1. Disable USB in LabVIEW Real-Time 8.2 and Later Versions: http://digital.ni.com/public.nsf/allkb/9171AF026183A6EB862571AB00820757?OpenDocument

Regards,

Ali M

Applications Engineer

National Instruments

[ericg · Accepted solution]

AnthonV,

Good question.  Fortunately, the BIOS is smart enough to leave USB keyboard support enabled for the duration of the boot process for the purpose of allowing users to enter and use the BIOS setup utility.  Before the BIOS hands over control to the OS (LabVIEW RT in this case), it disables legacy keyboard support if RT is selected as the boot target.

Note that when RT is selected as the boot target, USB keyboard support is disabled automatically by the BIOS on NI PXI/PXIe controllers.  So, there's nothing you need to do to ensure that you're using the optimal configuration for RT jitter.

Let me know if you need further clarification.

Thanks,

Eric Gardiner

Embedded Controller Group, NI R&D

[AnthonV]

Here is another scenario: If your Desktop PC has no PS/2 connector and you are installing RT from the USB utility disk - how do you select the 'format hard drive' option if the USB keyboard is now disabled?

[ericg]

AnthonV,

In the Desktop scenario (with no PS/2), you would need to complete the configuration in two steps:

1. With Legacy USB enabled, boot to the USB utility disk and format the hard drive.

2. Reboot, enter BIOS setup, and disable legacy USB in the BIOS.

On a normal Desktop PC, the Legacy USB setting must be managed by the user.  On NI's PXI and PXI Express embedded controllers, the Legacy USB setting is managed automatically when LabVIEW RT is the selected boot target.

Hope this helps,

Eric G.

[AnthonV]

Thanks Eric, on this specific PC activating the legacy USB didn't fix the problem - the keyboard was still dead.  It might be a bug in the BIOS.  I managed to get the hard drive formatted eventually by plugging it into another desktop that had a PS2 port, formatting it there and then plugging it back into the original PC.

Cheers