NI-CAN/NI-XNET Logfiles (.NCL) and How To Open Them

Updated Jan 6, 2023



  • NI-CAN

  • How do I log files in NI-CAN or NI-XNET?
  • How do I open .NCL files?
  • I am using NI-CAN for my application and I see it requires a .NCL file to read and write the frames that I'm acquiring. What is the NI-CAN Logfile and how do I open it to read my acquired data?

This NI-XNET logfile specification (.NCL) defines a simple, open, binary file format for storage of embedded network data (CAN, FlexRay, and LIN). The primary purpose of the logfile is usage within NI-XNET, NI-CAN and CompactRIO examples for logging, replay, and display of embedded network data. The NI-XNET logfile is also used within National Instruments tools, such as the NI-XNET Bus Monitor.

Note: Logfile created with the NI-XNET Logfile Specification cannot be used with application designed for the NI-CAN Logfile Specifications. NI-CAN Logfiles can be used with applications designed for with the NI-XNET logfile specification.


Examples for NCL continue to be installed with NI-XNET (examples\nixnet folder in your LabVIEW directory), but they no longer appear in the NI Example Finder. If you need to store multiple sources of data in a single file (for example, multiple CAN interfaces, or CAN with analog input), you should consider transitioning your application from NCL to TDMS. Because both file formats use the same raw frame data, the changes required for this transition are relatively small.
For more information, r​​​​​eview the NI-XNET Logfile Specification .


Review the NI-CAN Logfile Specification .

  • To write a logfile, you can run the example that ship with the NI-CAN driver: Net Interface Logging VI
  • To view a generated logfile, you can run the examples that ship with the NI-CAN driver: Display Logfile as Frames VI or Display Logfile as Waveform To view the data as a waveform chart, you must have a CAN database reference that describes the data.

For more information on the NI-CAN Logfile, refer to the specification provided in the NI-CAN documentation folder (typically \Program Files\National Instruments\NI-CAN\Documentation).

Additional Information

Although the NCL logfile format is supported for compatibility, the TDMS logfile format is recommended for new applications. For more information, refer to Embedded Network Data in TDMS .


DIAdem allows you to convert these filetypes with the Bus Log Converter . You can read more about it here: Converting a Logfile into the TDM Format.  You can also use other Third-Party Add-Ons to view and convert NCL Logfiles, such as: NCL and TDMS Viewer and Converter - WKS Informatik GmbH .