going to try open plc with simple setup first without module, however, are there I/O modules made for rpi thats is plug n play?

i saw something about a shield that was stackable, is there similar with schematics to download?
Quote 0 0
There aren’t any OpenPLC I/O shields for the Raspberry Pi. I believe that there might be some third party shields for the Pi, but probably they don’t use the same pins for inputs and outputs, which means that to use them with OpenPLC you would have to edit the OpenPLC hardware layer to work with the right pins 
Quote 0 0