For a compact and highly robust controller we have the highly capable controller and distributed I/O solutions from Yotta controls in stock.
The A52 controllers have a small sized form factor more akin to a smart relay but feature a high speed processor with multiple communication possibilities. Programming can be done in the free software with function block programming or ladder logic with communication for downloading and uploading via a built in USB port. They also have RS232, RS485 and WiFi connections and wireless remote options.
The controllers have a built in Modbus master and slave for communication to and from other devices. Yotta also offer a distributed I/O solution for use with the A52 controller or other controllers. Digital I/O options include transistor or relay digital inputs and outputs. Analogue I/O options include 0-10V, 4-20mA and thermocouple inputs. Output options are 0-10V or 4-20mA outputs. The distributed I/O modules share the same form factor as the controllers and support Modbus RTU or ASCII over RS485 as standard.
The software is free and can be downloaded along with the main catalogue from the download link at the right of this page.