Hi,
Is it possible to use the RT Modbus Server (recommended by NI for Modbus communication) on a NI-9871 (4 x RS-485) module? Since I need to do some FPGA programming on other I/O modules, the NI-9074 chassis is set to FPGA mode. To avoid too much FPGA programming, I've drawn the NI-9871 directly under "Chassis (NI-9074)" in the project. It means I use the chassis in hybrid mode.
The Modbus Server in the project is set to the serial port on the NI-9871. This port is not shown when chassis settings are deployed in FPGA mode, neither in MAX nor in the list of available VISA resources on the block diagram. But it appears when I run the VI "VISA Find Resource". Using the appropriate element of its result array with VIs of the Modbus library works fine.
Trying to access shared variables of the Modbus Server gives error -1967353900 (The Modbus I/O server failed to allocate a serial port. Ensure that the specified serial port is available.). Which somehow makes sense, since as described above, access to the port isn't straightforward.
Are there possibilities to set properties of the Modbus Server at run-time? There are also some configuration issues of the RS-485 communication (Wire Mode), I have to take care of and which do not appear in the Modbus Server configuration in the project.
Best regards,
Karsten
