Generic Serial or Ethernet IO

Hello all, hoping someone can jog my memory. I am looking for some IO blocks, approx 20 Outputs and 5 Inputs that can be controlled directly from Serial or Ethernet, i.e. not specific to any processor. I know i looked at these a while ago to give IO from a PC but now can't remember who the manufacturer or supplier were. I am hoping to run these from a robot which has both Ethernet and Serial ports (programmable within the robot code). Any pointers would be much appreciated.

I've used Opto 20's I think they were many years ago, not sure if they are still about or what the modern equivalent are. I would think there would be a lot of choices.

Weidmuller used to do IO which used a very simple ASCII protocol. I am not sure whether it is still available but it is worth a try. Alternatively Modbus is generally easy to implement if your processor can handle the CRC calculation. This used to be heavy going for many basic PLC's.

Andybr