CODESYS isn't a brand of PLC — it's the programming system inside hundreds of them. Learn it once and you can program WAGO, Festo, Eaton, ABB, and a thousand other targets. Pure IEC 61131-3, a device tree that abstracts the hardware, and a task configuration that runs the same POUs on anybody's CPU.
The idea that makes CODESYS unique: your IEC program is compiled against a runtime that vendors embed in their hardware — so the same POUs deploy to a WAGO, a Festo, an Eaton or a Raspberry Pi. Build one program and watch it download to three different targets, live.
The three Program Organization Units — Program, Function Block, Function — and how the Task Configuration calls them: cyclic, freewheeling, event & status tasks, priorities, and the watchdog. The CODESYS scan, demystified.
CODESYS speaks every IEC 61131-3 language plus the free-form CFC. The same logic in each, when to choose ST over ladder, and why CFC is loved for signal-flow that doesn't fit a grid.
CODESYS pushed OOP into PLC code: function blocks with methods & properties, EXTENDS for inheritance, INTERFACEs for polymorphism. Modern, testable automation code — and when it actually helps.
How CODESYS hides the hardware: the device tree, adding a fieldbus master, and mapping physical channels to variables. Swap the target device and your logic doesn't change — only the mapping does.
CODESYS as a fieldbus master: EtherCAT, PROFINET, EtherNet/IP, Modbus and CANopen, importing device descriptions (ESI/GSDML), and the cyclic exchange that feeds your I/O map.
CODESYS has an HMI baked in: draw screens, bind elements to variables, and serve the same visualization as a target display or a WebVisual in any browser — no separate HMI tool.
Motion in software: SoftMotion axes, the PLCopen MC_ blocks, single-axis moves, CAM profiles and CNC — all running on standard CODESYS targets without dedicated motion hardware.
CODESYS debugging punches above its weight: live monitoring, real breakpoints & single-stepping through ST, the trace recorder, write/force values, and the logfile. Debug like a software engineer.
The serious end: CODESYS Safety for certified SIL 3 applications on a separate safety runtime, plus securing a controller — encrypted communication, user management, and signed boot applications.
The funny-but-useful deep dive: why OT flips the security rulebook, the Purdue layer cake, real war stories from Stuxnet to Volt Typhoon, and a defense-in-depth attack simulator where you defend a water plant against the kill chain.
The platform deep dive: the CODESYS Development System V3 and the Control runtime embedded in 1000+ devices from 400+ manufacturers, plus the optional add-ons — SoftMotion, Safety, OPC UA, Visualization and the Automation Server — with an interactive stack.
Manage a whole fleet from the browser: register your controllers with the CODESYS Automation Server, push application updates over the air, and watch device health and live values from one dashboard. Now live — open it →