Attention

IronPLC can only run very simple programs. The steps described are accurate but many language features are not yet supported.

IronPLC and the IEC 61131-3 Ecosystem

This page explains where IronPLC fits in the broader world of PLC development tools.

The Traditional PLC Workflow

Most PLC manufacturers ship an integrated development environment (IDE) tied to their hardware. For example:

  • Beckhoff provides TwinCAT, which runs inside Visual Studio.

  • Siemens provides TIA Portal for its S7 family.

  • Codesys provides a vendor-neutral IDE that many smaller manufacturers rebrand (including the open-source Beremiz project).

These tools handle everything: editing, compiling, downloading to hardware, debugging, and visualization. They are powerful, but they are also proprietary, expensive, and locked to specific hardware.

What IronPLC Does Today

IronPLC is an open-source toolchain for working with IEC 61131-3 code. Today it provides:

  • A compiler (ironplcc) that parses and checks IEC 61131-3 programs for correctness. It catches syntax errors, type mismatches, and other problems before you ever download code to a PLC.

  • A VS Code extension that provides auto-completion, syntax highlighting and real-time error checking as you type.

  • A runtime (ironplcvm) that can execute simple compiled programs. The runtime is in early development and supports only a limited subset of the language.

IronPLC reads several source formats:

  • Structured Text (.st files) — the native text format

  • PLCopen XML (.xml, plc.xml) — used by Beremiz and other PLCopen-compatible tools

  • TwinCAT (.TcPOU, .TcGVL, .plcproj) — used by Beckhoff TwinCAT 3

This means you can point IronPLC at an existing project from Beremiz or TwinCAT and get a second opinion on your code without changing your workflow.

What IronPLC Does Not Do (Yet)

IronPLC is a young project. Some things it cannot do today:

  • Run on real PLC hardware. The runtime currently targets a virtual machine, not physical I/O.

  • Support the full IEC 61131-3 language. Many features are parsed and checked but code generation covers only a small subset.

  • Replace your existing IDE. IronPLC is a complement to your existing tools, not a replacement.

The long-term vision is to become a full development environment for building IEC 61131-3 based control systems that run on off-the-shelf embedded computers (sometimes called SoftPLCs). That goal is ambitious, and contributions are welcome.

How IronPLC Relates to Other Tools

Tool

Relationship to IronPLC

Beremiz

An open-source PLC IDE. IronPLC can read Beremiz project files (plc.xml) to provide additional checking. See Check Beremiz Projects.

TwinCAT

Beckhoff’s PLC IDE. IronPLC can read TwinCAT project files to provide additional checking. See Check TwinCAT 3 Projects.

Codesys

A widely used commercial PLC IDE. IronPLC does not currently read Codesys project files, but Codesys can export to PLCopen XML.

OpenPLC

An open-source PLC runtime. IronPLC and OpenPLC have different goals: OpenPLC focuses on running programs on hardware, while IronPLC focuses on checking and compiling code.