NI-CAN Device USB Led Blinks and Causes NI-MAX to Crash

Updated May 3, 2018

Reported In


  • USB-8473


  • NI-CAN


Reported in Windows 7 Operating System.

Issue Details

I connected a USB-8473 NI-CAN device to my computer. The device is correctly recognized both by Windows Device Manager and by NI-MAX.

However, the USB led is continuously blinking and any software operation in NI-MAX (such as launching Bus Monitor or performing a Self Test) causes NI-MAX to crash with the following error message:

Exception context: Function=CmxAggregateItemUI::InvokeCommand Plugin=CanUI.mxx 

Sometimes it is impossible to close NI-MAX application, which can be closed only after unplugging the USB CAN device.


To troubleshoot the issue, try to perform the following tests: If none of these steps solve the error, please contact National Instruments Technical Support. Also, take note of any repetitive pattern in the USB LED blinking: count the number of long and short flashes.

Additional Information

Before upgrading any drivers, be sure that your hardware is compatible with the new version of the driver. This information can usually be found in the driver readme provided on the download page.

The blink pattern for the USB-CAN devices provides the status codes returned by NI-CAN functions. You can interpret the pattern by using the count of slow blinks as the high nibble of a byte, and the fast blinks as the low nibble of a byte. This is shown below. 

  • 2 slow blinks followed by 4 fast blinks
    • Byte is 0x24
  • 4 slow blinks followed by 8 fast blinks
    • Byte is 0x48
The resulting byte is the least significant byte of the status code returned by NI-CAN functions.