I purchased this Relay PI-Plate and it works very well using python. I though I could expand its uses with codesys and make my own driver. I emailed the support and asked for a C library or if they would explain more about how the driver works. They said no they would not help, develop a C library. The python library was the only thing they would supply, but I was welcome to develop my own library based on their python library. I read how to develop a SPI bus device driver on the forge and though I would give it a shot. Below is what I discovered so far.
My main goal would be to add a device under the SPI bus master and map each relay to a boolean value. Also the relay. I would like to get also poll all the board information and map that to a variable.