Solution
This issue can be caused because some third party devices do not implement all serial settings on their USB-Serial adapters. To avoid the problem, do not use the VISA Configure Serial Port VI in your program. Instead use a VISA property node to set only the supported properties.
To determine which properties are unsupported by your USB-Serial adapter, use a VISA property node, and set the properties one at a time to see which properties cause the I/O error to be thrown.
The VISA Configure Serial Port VI sets the properties displayed in the image below (where grey inputs are optional).
To instead set these properties with a property node, place a VISA Property Node on your block diagram. Select
Property on the node and navigate to one of the following sub-menus:
- Serial Settings to set baud rate, data bits, parity, stop bits, or flow control
- Message-Based Settings to set termination character enable or termination character
- General Settings to set timeout
From there, select the property you would like to set. Then select the property node, right-click and select
Change All to Read (if it's not already selected). Now you can input a constant or control to that property.
In general, if the unsupported property is needed by your application you should contact the manufacturer of the device. National Instruments USB-Serial devices do not have this limitation.
Unsupported TimeoutIf you find that the unsupported property is the timeout. A potential workaround is to modify
visaconf.ini by adding the token:
WriteTimeoutGranularity = 0
under section [ASRL-RSRC-ALIAS], as shown in this image:
Visaconf.ini can be found at C:\ProgramData\National Instruments\NIvisa.