Generating automatically the documentation from PLC code by D4T3 to improve the usability and life cycle management of software in automation

D4T3 (i.e. Doxygen for TwinCAT3) was developed to generate automatically the documentation from a set of documented and/or undocumented PLC source files. D4T3 documentation was designed to support traditional PLC-world features (e.g. inputs, programs, tasks, etc.) and more recent Object Oriented features of IEC61131-3 (e.g. interfaces, inheritance, etc.). Moreover, this documentation was designed to be generated as an on-line manual (i.e. HTML) and/or as an off-line reference manual (e.g. LATEX, CHM, etc.). The usability, maintainability and understanding of documented PLC software was found significantly improved when the software was provided with its D4T3 documentation. Additionally, D4T3 reduced the time spent on documentation and managed the differences among versions. Thus, the automated documentation generator can be used to simplify/overcome the usability and life-cycle-management challenges in automation. It can also lead PLC vendors to design a common tool to generate the PLC software documentation supporting system engineers and software engineers in automation.