Communication problem with LabView MODBUS on cRIO-9035 using serial RS-485 port

[michal_timm]

Hi,

I'm trying to implement communication between cRIO-9035 and Kinco FD422S servo controller. I tested communication from PC using NI OPC server with USB - RS485 converter and everything works OK. The problem is in implementing communication from real-time target cRIO-9035.

I tried using LabView Modbus API from Real-Time Module as well as Modbus I/O Server and also unofficial MODBUS Library for LabVIEW. In all cases I wasn't succesfull. I hooked up an oscilloscope and find out strange distorted frames. Please advise me what could be the reason for that?

I wired RxD- with TxD- togehter as well as RxD+ with TxD+ on both ends of cable. I tried connecting and disconnecting grounds.

With Slave connected to cRIO RS-485 port:

With Slave disconnected from cRIO

My RT vi is like that:

[bu_ziangzhang]

Hello,

I encounter the same problem, have you fixed it to the end?

Thanks!