Installation & Quick Start

Requirements

  • VS Code 1.85 or later — Download VS Code
  • Platforms: Windows, Linux, macOS (all platforms supported by VS Code)
  • TwinCAT 3: Optional — the extension works standalone with any .st file. TwinCAT project integration (.tsproj / .plcproj) enables cross-file Go-to-Definition.
  • Node.js is not required — the extension bundles its own language server.

The canary release provides the latest pre-built .vsix package. This is the recommended installation method until the extension is published on the VS Code Marketplace.

Step 1 — Download the .vsix

Go to the canary release page and download the latest st-lsp-*.vsix file.

Screenshot placeholder: Release page showing the .vsix asset under “Assets”.

Step 2 — Install in VS Code

Option A — Command line:

code --install-extension st-lsp-*.vsix

Option B — VS Code UI:

  1. Open VS Code.
  2. Go to the Extensions view (Ctrl+Shift+X / Cmd+Shift+X).
  3. Click the ⋯ menu (top-right of the Extensions panel).
  4. Select Install from VSIX…
  5. Browse to and select the downloaded .vsix file.
  6. Click Install and reload VS Code when prompted.

Screenshot placeholder: Extensions panel with “Install from VSIX…” menu option highlighted.

Installation from VS Code Marketplace (Upcoming)

Note: The extension is not yet published on the VS Code Marketplace. Marketplace installation will be available in a future release.

Once published, you will be able to install directly from VS Code:

  1. Open the Extensions view (Ctrl+Shift+X / Cmd+Shift+X).
  2. Search for ST LSP.
  3. Click Install.

Installation from Source

Use this method to build the extension yourself from the latest source code.

Prerequisites: Node.js 18+ and Git.

# Clone the repository
git clone https://github.com/pirminbleiker/st-lsp.git
cd st-lsp

# Install dependencies
npm install

# Compile TypeScript
npm run compile

# Package the extension into a .vsix
npm run package

This produces a st-lsp-*.vsix file in the project root. Install it using the same steps as above:

code --install-extension st-lsp-*.vsix

First Steps / Quick Start

1. Open your project

Open a TwinCAT project folder or any folder containing .st files in VS Code:

  • File → Open Folder… and select your project root.

2. The extension activates automatically

The language server starts automatically when you open any of these file types:

Extension Description
.st / .ST Standard IEC 61131-3 Structured Text
.TcPOU TwinCAT POU file
.TcGVL TwinCAT Global Variable List
.TcDUT TwinCAT Data Unit Type
.TcIO TwinCAT I/O mapping
.TcTask TwinCAT Task configuration

3. Try the features

Feature How to use
Code completion Press Ctrl+Space inside a ST file to trigger suggestions
Hover documentation Hover the cursor over any symbol (variable, type, function block)
Go to Definition Press F12 or right-click → Go to Definition on a symbol
Workspace symbol search Press Ctrl+T and type a symbol name to jump to its definition
Diagnostics Syntax errors appear as red underlines with details in the Problems panel

4. TwinCAT project integration (optional)

For cross-file Go to Definition, open the workspace root that contains your .tsproj or .plcproj file. The extension automatically scans and indexes all ST source files in the project.

Configuration

The extension works out of the box with no required configuration. The following optional settings are available:

st-lsp.twincat.installPath

   
Type string
Default "" (auto-detect)
Example C:\TwinCAT\3.1

Path to the TwinCAT installation directory. When set, library references from .plcproj files are resolved from the Managed Libraries folder (<installPath>/Components/Plc/Managed Libraries/).

Auto-detection: If this setting is left empty, the extension attempts to locate the TwinCAT installation automatically by checking:

  1. The TWINCAT3DIR environment variable.
  2. Common installation paths on Windows / WSL2.

Set this explicitly when auto-detection does not find your installation, for example on non-standard install paths.

VS Code settings.json example:

{
  "st-lsp.twincat.installPath": "C:\\TwinCAT\\3.1"
}

Other LSP clients: Pass the path as twincatInstallPath inside the initializationOptions object when starting the language server.