Modbus Plus

I have a project I will be bidding on that has 74 nodes (PLCs) on a Modbus Plus Network. These nodes will be converted one at a time to MB Ethernet which will work with the OPC-UA server just fine. My question is what is the best way to communicate with these nodes till then. I want to run the Ignition system on Linux which would pose a problem with an OPC such as Kepware talking to the PLCs. Can I run Kepware as an OPC-UA server then have Ignition talk with that.

My thoughts are this config.

Server Class BOX (16G RAM) running ESX.
1 VM as Ignition running on linux
1 VM as MySQL running on linux
1 VM as OPC server running on XP-PRO

Any feedback would be appreciated.


That configuration will work nicely. Just make sure you are using Kepware 5.2 or above since that version has OPC-UA. You can follow this how-to on how to connect Ignition to Kepware using OPC-UA:

Make sure you give enough memory to both the Ignition and MySQL VMs to allow for expansion later on. Give each VM a static IP so you won’t have any communication issues.

As you convert PLCs one at a time you can remove it from Kepware and add it to Ignition. All you have to do in Ignition is do a search and replace on the OPC Item Path.

If you have any further questions let us know.

I was planning on giving Ignition 6G, MySQL 6G, and XP (Kepware) 2G.

The reason I want to configure the system this way is I can move each to there own boxes if I need to because of performance.

Right, that is a good approach.

I just want to chime in and remind you to use a 64-bit linux distro (Ubuntu Server 64-bit is what we test on) and make sure you are using 64-bit Java and the 64-bit Ignition package. Otherwise you won’t be able to take advantage of the RAM you are allocating for the Ignition VM.

Thanks for your input, I had already planned on using it so I could take advantage of the memory.

On question does MySQL run faster on 64 bit???

It does run better on 64 bit in my experience. Make sure you are using the latest version of MySQL (5.5+) since there has been several improvements.

I’m considering switching to Ignition but I am having a similar situation trying to connect to a Modbus plus network. I have an existing GE Industrial Gateway OPC Server 7.52 , but am unable to connect to it from within Ignition. Here is the error I get: COM object method returns error code: 0x800706BA; The RPC server is unavailable.

A better solution would appear to be an ethernet bridge of some sort anyway; Is there an Ethernet/Modbus Plus bridge that someone has used with success in conjunction with Ignition? Or do I have to get a Kepware OPC-UA Server?

We have multiple Niobrara R&D MEB ModbusTCP to Modbus Plus bridges.

I have Ignition talking to Modbus Plus PLCs via Niobrara.

I didn’t have to modifiy the Niobrara bridges at all. All I needed to know were the indexes of the PLCs.

They were already setup for our existing batching system, which is pushing 15 years old.

Lots of custom Unix code, running on HPUX.

Wish Ignition had been around back then.

Hope this helps.


That’s great to hear since that appears to be the cleanest always on approach. Thanks Dennis.

Just to chime in quickly to comment on your OPC-COM error: that’s likely just standard DCOM problems that need to be sorted out. You can basically read it as “The opc server isn’t available”. Why? Maybe because Ignition is running as system (since it’s a service), and the GE server isn’t. There are a lot of other possible causes, though, so I’d recommend searching the forum for DCOM and going through some of the suggestions.

But beyond that, OPC-UA or a modbus gateway would be a more future-proof way to go (DCOM is often broken by microsoft updates).


Just another comment about GE’s IGS. Its nothing but Kepware relabeled.