I am trying to learn Ignition for work. I thought hey lets see if I can make an Arduino using a Modbus Serial RTU library talk with Ignition.
I thought it was weird that the Modbus RTU driver is not more heavily advertised, found out that its hidden in the Serial Gateway module from a post.
I used this Arduino Modbus Library https://github.com/andresarmento/modbus-arduino
I recommend the user get QModbus or something equivalent to test that they have their Arduino sketch setup correctly.
Once you install the Serial Gateway Module in Ignition and have ability to make a Modbus RTU device.
Go make some OPC tags, just be mindful that the SlaveID that you setup in the Modbus Aruduino Sketch must Match the UnitID when you address your tag.(See the Ignition documents for Setting up UnitID addressing)
If people want sample sketch or sample tags let me know. I atleast wanted to get the concept out that you can use Existing Arduino Modbus Serial Library and over the USB cable get data into Ignition. The tricky part is not forgetting about the SlaveID must match UnitID when you address your tags in the OPC Browser.