Codesys, Seen From TIA Portal

Why this guide exists

Most of my work is Siemens. But Codesys sits underneath a large share of the PLCs that are not Siemens, and I did not want my picture of it to come from other people’s opinions.

So I am working through it myself and writing down what a TIA Portal engineer actually notices — where Codesys does something better, where TIA Portal does, and where the difference is just a habit you have to unlearn.

I am not a Codesys specialist and I do not present myself as one. That is the point of writing it in public: if you deploy Codesys for a living and something here reads wrong, the comments are open and corrections make the work better.

The series, in order

These build on each other, so reading them in sequence works best.

1. Why I’m Studying Codesys — And What a TIA Portal Engineer Actually Sees — the IDE and runtime split, who owns CODESYS GmbH, and the cost structure.
2. Inside a Codesys Project — Devices, Applications, POUs, and the Habits Worth Unlearning — Devices view versus POUs view, and why there are two project trees instead of one.
3. Codesys ST vs Siemens SCL — The Language Differences That Catch You First — the # prefix, the stat naming convention, the two-pane editor.
4. Where Codesys Actually Runs — Runtime Targets and the Hardware Story — why the IDE and the runtime are separate products, and what running IEC 61131-3 on something that is not a vendor PLC looks like.

If you came here from Siemens

The comparison only makes sense if you know what you are comparing against. Two companion guides written from the same starting point: TIA Portal, the platform I use for most customer work, and SIMATIC AX, Siemens’ text-based toolchain.

Away from the PLC platforms entirely, Custom Devices covers the electronics and operator interfaces I build myself when nothing off the shelf fits.

Working on something similar?

I am Yuriy Mosiyenko — I design and program industrial control systems, mostly Siemens, as a one-person practice based in Bedford, Nova Scotia, working with customers across Canada. If you have a controls project you cannot staff internally, tell me what you are building.