Error -1950678962 Remotely Reading or Writing I/O Variables in LabVIEW

Issue Details

I am using the Scanned Variable Write VI in LabVIEW to remotely write to the I/O variables available in my Ethernet expansion chassis. For instance, if I have an NI-9474 module inside my NI-9149 Ethernet chassis, I observe the following error running the code either on a Real-Time (RT) controller target (i.e., cRIO-9058) or in my host computer.

Error -1950678962 occurred at Scanned Variable Write in Main.vi

Possible reasons (s): 

LabVIEW: (Hex 0x8BBB004E) The specified variable does not support the specified read, write, or open operation.

Solution

The Scanned Variable Write and the Scanned Variable Read VIs allow you to write/read I/O variables inside your RT controller or expansion chassis. However, these VIs only support access to local I/O variables. Remote I/O variables are not supported. For instance, if you have an NI module inside your RT controller, you could use the Scanned Variable Write VI to write to any of the I/O variables in any of the modules. The image below shows an example of the Main VI (inside the RT controller - cRIO-9058), using the Scanned Variable Write VI to write to the DOO of the NI-9472 available in slot 5. 

You can use the PSP Variable Engine and the Write Variable VI to remotely access the I/O variables of the remote target (Ethernet expansion chassis in this example).

Additional Information

You can use either the PSP Variable Engine or the I/O Variable Engine to access a network-published I/O variable or I/O alias. Use the I/O Variable Engine ni.var.io to read or write a network-published I/O variable or I/O alias locally. Use the PSP Variable Engine ni.var.psp to read or write a network-published I/O variable or I/O alias remotely.