I’ve managed to dodge OPC and PLCs until now.
What do I need to connect to a MicroLogix 1100?
It will be connected to RSLogix 500.
It has a MicroLogix Communication Interface Module with web server functionality.
Can I talk directly to it with OPC-UA and the right driver? Do I have to go though the RSLogix app?
You can talk to it directly with the MicroLogix driver and the OPC-UA module.
That’s what I was hoping for 
Where do I get the driver from? I can’t find a driver download section.
The Allen-Bradley drivers come with the standard installation of Ignition. Just go into the Gateway Config section and select Devices under OPC-UA and add a driver. The MicroLogix driver will show up in that list.
Just found them. Thanks 