MODBUS RTU connection issue

Hello, everyone:
I am new to ignition and I was trying to connect a MODBUS device on my desktop but could not connect to it. Here is my setup:

  • Ignition installed on my desktop: Version 7.8.3 (b2016061017) 64 bit
  • Desktop running Windows 10, 64 bit
  • Module Installed: Serial Support Client 3.8.2 (b2016030813)
  • Module Installed: Serial Support Gateway 3.8.2 (b2016030813)
  • Connection: FTDI USB-to-RS485 cable

What I want to do is a very simple task. I want my desktop connected to a MODBUS RTU device via RS485 cable. And read real-time data using ignition in web browser like localhost:8088

Desktop PC (Ignition 7.8.3) <-------- RS485 ------------> MODBUS RTU Device

Here is what I did:

  1. Install Serial Support Gateway and Serial Support Client modules. Then reboot my computer so I can see the MODBUS RTU type in the device window;
  2. Log into Ignition, Config Tab>> OPC-UA Server>>Device, then clicked “create new Device”,
  3. Select MODBUS RTU type, then type in “Serial Port” to COM5, which is the com port the FTDI USB-to-RS485 cable emulated; Set baud rate to match my Modbus RTU device, e.g. 9600, 8, N, 1 etc.
  4. Click “Create New Device” button. But the device status always show “Disconnected”.

I tried unplug/plug back the USB cable, reboot computer, restart serial modules. Still shows “disconnected” in Device Status.

What steps was I missing to make it work? Any suggestions are welcome. Thanks in advance!


I know this is post is getting a little long in the teeth, but I was curious if you were ever able to get this working.

If not I’d be curious to know if you were able to connect to the PLC using a standalone modbus program.

If it is still relevant, there was a bug in 7.8.3 that broke the Modbus RTU driver, which was fixed in 7.8.4.