Custom Serial Protocol?

Hi again everyone,
Well, in the process of connecting my various devices to ignition, I discovered that a couple of controllers that my old SCADA system was talking to don’t support Modbus. :open_mouth: Crap!

I found a copy of the manual for the controller and it looks like it has some sort of custom protocol for communications. Link to manual:
The serial info is in Appendix B, page 101. The juicy details of the protocol start on page 110.

That isn’t the exact controller I have, but the protocol is the same. Is it even possible to connect ignition to this? I’m not clear on the capabilities of the TCP driver or the Serial Module. I can get an Ethernet to Serial adapter similar to the Modbus gateways I’m using for my other serial devices, but I’m not sure how to go about setting up actual communications with this thing, or if it’s even possible.

How badly am I screwed here?


I have not used the TCP/Serial module from Ignition, but what I do use is Kepware’s UCON driver to communicate with serial devices through a DigiPort.

Here is how you do it in Kepware.

I will keep that in mind, but I was hoping to avoid using Kepware. It’s Windows only, which I was trying to avoid for this install, and I’m not using it for anything else. I’d rather not have to buy it just for these. I understand that I will probably need to buy the Serial module for ignition, but I would rather spend my money there. The big problem is the scripting.

I think if I get something like a Moxa Nport 5232 and ignition’s Serial module, I can talk directly to the device over ethernet. At that point, it should be a matter of writing some jython to handle the communication protocol. I know it won’t be simple; I’ve never touched jython (or python) before, but I’m willing to make this work.

Once I have the Moxa, or similar, installed and wired, I’ll probably be posting back with more questions regarding jython scripting. If anyone wants to give me pointers in the mean time, I’ll take whatever I can get :slight_smile:


We use the serial module quite frequently with MOXA Nport devices. The gateway serial module is used and is driven from tag value change scripts on tags (as opposed to gateway resident tag change scripts). Driving the port from tag value change scripts allows visibility of the processing and great flexibility ref scan class, device comm latency, etc. Bear in mind the serial module is rather primitive and one really needs to understand the comm processing of the end device. To this end, we normally start the process with comm analysis using serial data breakout software between the end device and the MOXA Nport. We usually use Eltima for this RS232, 485, or 422). When dealing with MODBUS, RTU Master from is an excellent tool for much the same purpose.

Good to hear you are successfully doing serial communications similar to what I need to do.

I’m not sure I understand what you mean by “tag value change scripts on tags (as opposed to gateway resident tag change scripts)”. I’m guessing I’m just unfamiliar with the lingo and am missing something simple. Could you expand a bit on this? Actually, any info about what code goes where would be helpful.

I’m hoping that the manual I have (basically identical to the link I posted) will be enough to let me write what I need to talk to these devices.