Why Is My cRIO Assigning New Values to USB and SD Flash Drives?

Updated Jun 19, 2018

Reported In


  • cRIO-9030

Issue Details

When a USB or SD flash drive is removed and replaced the controller keeps assigning them a new letter instead of reusing the old ones (letter U: for the first drive, V: for the second, and so on).

This causes issues when the controller switches to storing data on the local drive when it runs out of letters to assign.



There are a few suggestions to try and resolve this issue:
  • Reboot the controller.
  • Update the controller to the newest firmware. Currently firmware updates are distributed with the specific device driver (e.g. a cRIO-9068 will have any firmware updates distributed with the NI CompactRIO Driver).
  • Ensure the USB is directly connected (without USB Hubs etc.)
  • Check the file format and size is compatible. All NI Real-Time devices support FAT32, and this format is recommended for ease of transfer to Windows. FAT16 has a 4GB limit on partition size, whereas FAT32 has a 2TB limit on partition size. OS specific compatibilities are below:
    • For PharLap systems, external USB drives can use either FAT32 or Reliance file formats.
    • On VxWorks, the only supported format is FAT32.
    • For LinuxRT, external USB drives should be formatted as be FAT32. For raw NAND devices UBIFS is accepted.

Additional Information

A suggested workaround:

Save the name of each USB to an INI file present in a consistent location in the USB. Use an INI file check in order to identify the USB drives.