NI-VISA Function Hangs If I Use Third-Party USB Serial Adapters

Updated Oct 5, 2022

Reported In


  • LabVIEW



Issue Details

NI-VISA Read/Write function hangs if I use third-party USB serial adapters. Why does this happen? Is there any way to fix this problem?


As written in the document about third-party USB serial adapters, some USB-to-serial adapters do not support asynchronous I/O. VISA functions use asynchronous mode as default, this causes hang up when read/write functions are called.
You can avoid this behavior by selecting Synchronous in Synchronous I/O mode as shown below, or using 'Byte at Port' to specify the number to read.