What is Codesys?
The OG Soft PLC
CODESYS (short for Controller Development System) is a widely used IEC 61131-3-compliant software suite for developing automation logic. It lets engineers write control programs in standard languages such as Ladder Diagram (LD), Structured Text (ST), and Function Block Diagram (FBD).
Unlike vendor-locked tools (e.g., Siemens TIA Portal or Rockwell Studio 5000), CODESYS is hardware-agnostic, meaning it runs on controllers from many manufacturers—or even on PCs as a Soft PLC.
Joyful Thoughts
This section shares James Joy’s perspective on how this technology applies specifically to industrial automation.
CODESYS represents a step in the right direction—away from closed IDEs tied to a single hardware vendor. If I had to choose any proprietary PLC platform on the market today, I’d choose CODESYS.
That said, it’s still a closed ecosystem. It tries to centralize all software development within its IDE, which slows the adoption of modern engineering practices like version control, continuous integration, and continuous deployment.
Industrial controllers should embrace the open-source ecosystem, where these capabilities already exist and evolve rapidly. That’s a big part of why we developed Tentacle.