Guidance on Ignition and Modbus RTU over TCP

Ignition
1

Hi, I have a GE Multilin 469 that can communicate via Modbus RTU. It's connected to a MOXA N5232 via RS 485 (2 wire) and the MOXA is connected to a network switch over ethernet. The Multilin is configured as slave address 11. I am trying to map the Modbus addresses of the multilin to Ignition to read values. I can successfully connect to the MOXA from Ignition via Modbus TCP or Modbus RTU over TCP. However, I am unable to pass the slave address of the Multilin to Ignition to initiate communication. I have tried setting the unit id of any modbus addresses to 11 and even specifying the addresses on my OPC tags as [devicename]11.HRXXX. Any ideas on how I can do that?

2

It looks like this is a serial-to-ethernet converter, not a Modbus gateway, so you need to make sure you're using the Modbus RTU-over-TCP driver.

This is the right approach. If it's not working you may have a configuration error on the converter or something else is wrong. Can you communicate through this converter using any other Modubs client software, like modpoll, etc...?

3

Also look at the "Force Transmit" settings in the Moxa. My alternate driver's user manual has an appendix with recommendations:

https://www.automation-pros.com/modbus/UserManual.pdf

4

6 posts were split to a new topic: Modbus via NPort 5110

10

It did turn out to be a configuration error. Thank you for your help.

11

Thank you for your suggestion. It helped

1 Like
12

I have the same problem, how did you fix it?

In my case I have a gateway modbus connected to the factory network (modbus TCP salve) and behind this gateway (Modbus rtu master) the modbus RTU devices.

I've configured the device Modbus RTU over TCP with IP and port (if I define local address, later the connection is not possible)

Later on "address", I define Prefix: CO2, Start:1, End:2, step: yes, UnitID:1 (for rtu slave #1), Type: Int16 holding register and Input register, ModbusAddress:1. This is just the configuration I have on my current BMS and I'm checking if Ignition can do the same functions, but I don't get it. (Error_Configuration"Bad_NodeIdUnknown:the node id refers to a node that does not exist in the server address space)

And other thing, how often these parameters are updated? Because I didn't see any refresh frecuency parameter.

Many thanks in advance