I am using the NI 9871 module in a cRIO-9066 chassi to do Modbus communication.
I have deployed Modbus I/O Server 16, NI-VISA 16, NI-VISA Server 16, NI-Serial 9871 Scan Engine Support 15 to the Realtime system (and of course a lot of other packages)
When I try to use read a variable from the Modbus I/O Server (regardless whether on the host or on the target) I get the error -1967353900 (The Modbus I/O server failed to allocate a serial port) The vi I use does nothing except reading a Modbus I/O variable.
I can open the serial port I am using with the VISA Test Panel, and manually send a Modbus command to the device I am trying to communicate with, and receive a correct Modbus answer.
I have read "Troubleshooting Modbus I/O Servers" but it does not help me.
Does anyone have an idea what the problem is?
(I have an ongoing service request on this issue, but I thought it would be useful to ask the communutiy at the same time)