RS232 Modbus RTU - LabView 2017 RT in LabVIEW General Posted December 6, 2018 · Report reply Hi all, I'm working with CompactRIO 9045. This plc is equipped with the rs232 and the rs485. I need to communicate with two devices in Modbus RTU. I have no problems with RS485 (ASRL2::INSTR) communication. This is initialization VI: I do the same operation with rs232 port (ASRL1::INSTR): But I have this error: Error -1073807246 occurred at Property Node (arg 1) in SubVIs.lvliberial Shared Components.lvlib:Configure Serial Port.vi->SubVIs.lvliberial Master.lvclass:Initialize Master.vi->Modbus Master.lvclass:Initialize.vi->Modbus Master.lvclass:Create Master Instance (Serial).vi->readExdSh1.vi Possible reason(s): VISA: (Hex 0xBFFF0072) The resource is valid, but VISA cannot currently access it. The resource can't be occupied... I have seen all national guides and tutorial, but I don't find the solution. Can you help me? Thank you.