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Abstract

This tutorial details how to connect existing Modbus RTU devices over a serial network into the Ignition Modbus TCP driver using a third party serial to ethernet gateway.

For this tutorial we are using the MGate MB3170/MB3270 Series Gateway from Moxa which is readily available for purchase from Amazon.



MGate Topology and serial connections

The image below shows an example of how Modbus RTU Devices would be connected through the Moxa gateway.


The gateway uses male DB9 serial ports to connect to the Modbus RTU or ASCII devices.

Each port supports three serial interfaces: RS-232, RS-422 and RS-485 (both 2 and 4 wire) with the pinout shown below:


MGate Configuration

Initial Configuration Access

Moxa provide a Windows based utility that can be used to connect to the MGate and aid in configuring the unit. But the MGate also provides a native web UI that provides the same functionality from any operating system. Out of the box the MGate will have the following default TCP/IP address and default Account and Passwords:


Temporarily set your computer’s Ethernet domain to the 192.168.127.xxx domain. Once you have done that, open a web browser and browse to http://192.168.127.254. That will result in the following web page being displayed:


After you enter the default admin/moxa credentials you will be prompted to enter a new password. 

This is the password that you will need to record and keep for future access to the MGate unit.

Setting a Static IP Address

Once you have logged into the MGate unit, navigate to the “Network Parameter” tab within the web UI. The MGate unit provides for both DCHP as well as STATIC IP settings. Because we want the MGate to reliably appear at a known IP address after things like power outages and resets, it is best to configure the device with a known STATIC IP address. 



  • Under the “IP Configuration” drop down in the Web UI, select “Static”.
  • Enter a Static IP address that makes sense in your network topology. In this example, we have used 192.168.1.96
Once we get a static IP assigned to the Moxa MGate unit, we can revert our computer from the Moxa default IP domain to it’s typical DHCP/fixed IP address. 
  • Set the Netmask to what makes sense in your network topology (typically this will be a 255.255.255.0 setting)
  • Finally, setup a Gateway IP address. Note, in typical use cases routing thru a Gateway will not be used.
  • The DNS1 entry can default to the Gateway IP set above in most use cases.
  • Once all of the entries have been made, click on the “Submit” button to activate these settings.
In most use cases you will now that to set the Ethernet interface for your computer back to the typical network settings it was originally using. The MGate Web UI will now be accessed thru the new TCP/IP address that you assigned.


Configuring the Serial Port


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