To do Real-Time serial communication, it is recommended to use an on-board serial port or use an NI PXI
Serial Interface Module to add serial support to your device.NI USB-to-Serial Converters
converters are not supported as serial interfaces for Real-Time Operating Systems and will be identified as a USB RAW device rather than as a serial port. It is still technically possible to use NI-VISA to control USB RAW devices in Real-Time
It may be possible to install the driver for some 3rd-party USB-to-serial converters and some NI community users have tested some converters successfully
. However USB-to-Serial converters from vendors other than NI are not supported and are not guaranteed to work in LabVIEW Real-Time.