The Fourth Industrial Revolution or Industry 4.0 (I4.0) represents the evolution of the current productive systems from the merge of industrial automation and informatics. The technical innovation of I4.0 is characterized by the integration of manufacturing systems, management over the product life cycle and the decentralization of computing resources. The Reference Architecture Model for Industry 4.0 (RAMI 4.0) defines the compatible elements of I4.0 in a three-dimensional layer model. Despite its acceptance, the use of RAMI 4.0 is still restricted to research institutions and cases of individual executions. This paper focuses on the development of an open source controller interface for I4.0 based on RAMI 4.0 and OPC UA protocol. This interface should provide the functionalities of programming, RFID identification, network communication and equipment supervision, providing real-time process information, in a standardized and interoperable way, for any type of platform connected to the network. The paper describes the integration of technologies in the controller interface, as well as the controller relationship to the RAMI 4.0 layers. In addition, this controller interface represents the first step towards the development of a compatible “control device” to support I4.0 applications.