Continuous Integration for PLC-based Control System Development

Continuous Integration and Continuous Deployment (CI/CD) is a software engineering methodology which emphasises frequent, small changes committed to a version control system, which are verified by a suite of automatic tests, and which may be deployed to different environments. While CI/CD is well established in software engineering, it is not yet widely used in the development of industrial controls systems. However, the advantages of using CI/CD for such systems are clear. In this paper we describe a complete CI/CD pipeline able to automatically build Siemens PLC projects from sources, download the program to a PLC, and run a sequence of tests which interact with the PLC via both a Simulation Unit Profibus simulator and an OPC UA interface provided by Simatic NET. To achieve this, a gRPC service wrapping the Simatic API was used to provide an interface to the PLC project from the pipeline. In addition, a Python wrapper was created for the Simulation Unit API, as well as for the OPC UA interface, which allowed the test suite to be implemented in Python. A particle accelerator interlock system based on Siemens S7-300 PLCs has been taken as a use case to demonstrate the concept.