CODESYS is not a brand of PLC. It is the programming system inside hundreds of them. Learn it once and you can program WAGO, Festo, Eaton, ABB and a thousand other targets. You get 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 sets CODESYS apart: 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 live to three different targets.
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. This is the CODESYS scan, explained plainly.
CODESYS speaks every IEC 61131-3 language plus the free-form CFC. You see the same logic in each, when to choose ST over ladder, and why people like CFC 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. The track shows how to write testable automation code with it, and when OOP 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 only the mapping changes; your logic stays as it is.
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 built in: draw screens, bind elements to variables, and serve the same visualization as a target display or as a WebVisu in any browser, without a 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 is better than you might expect from a PLC tool: live monitoring, real breakpoints & single-stepping through ST, the trace recorder, write/force values, and the logfile. You debug the way a software engineer would.
The serious end: CODESYS Safety for certified SIL 3 applications on a separate safety runtime, plus securing a controller with encrypted communication, user management and signed boot applications.
A funny but useful deep dive: why OT flips the IT 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. It is live now: open it →