What is the Default Buffer Size for the System on Module?

Updated May 15, 2023

Reported In


  • CompactRIO System on Module
  • sbRIO-9651


  • LabVIEW



Issue Details

I need to know how large the buffer size is on my System on Module (sbRIO 9651)'s serial port 1. Where can I find this?


The buffer size depends on the operating system that you are using with your module, since the serial ports (or COM ports) are managed by the operating system. 

You can use the VISA Set I/O Buffer Size Function to manually set the buffer size if you are using your module with Windows. If you are using it on Linux Real-Time, you will not be able to use this function since NI-VISA does not have the capability to change the buffer size that the OS allocates for the serial port.

The best way to determine the default buffer size of your device on your OS is to run an I/O trace and view the contents of the buffer. See the document in Related Links for instructions on how to run an I/O trace.