Questassure VHDL Extension for VS Code

The official extension is available on the VS Code Marketplace.

This extension integrates Questassure VHDL productivity tools directly into VS Code, providing syntax highlighting, real-time diagnostics, formatting, simulations, interactive schematics, and FSM design tools.

🚀 Installation & Prerequisites

To use this extension, you need GHDL, Yosys, and Surfer installed on your system.

1. macOS

Install all dependencies via Homebrew:

brew install ghdl yosys surfer

2. Linux

Install via your package manager:

sudo apt update && sudo apt install ghdl yosys
cargo install surfer

3. Windows

Download and extract OSS CAD Suite (bundles GHDL and Yosys).
Download Surfer.
Add the bin folder of OSS CAD Suite and the folder containing surfer.exe to your environment PATH:
- Press the Windows Key, type environment variables, and select Edit the system environment variables.
- Click Environment Variables....
- Under User variables or System variables, select Path and click Edit....
- Click New and add the absolute paths to those folders.
- Click OK on all windows and restart VS Code.

✨ Key Features

1. Smart Editing & Formatting

Syntax Highlighting: Custom Questassure VHDL theme.
Auto-Save: Automatic save after 1000 ms of inactivity.
Real-time Diagnostics: Linting with GHDL, sensitivity list checker, and latch detector.
Code Formatting: 4-space indentation, colon alignment, and conditional <= alignment.

2. Visual Tools

Interactive FSM & RTL Schematic: Renders logic gates and state diagrams from code with two-way cross-probing.
FSM Designer: Graphically design, edit, and save FSMs directly as VHDL code.
Embedded Waveform Viewer: Built-in SVG-based waveform panel with layout presets.

3. Test Explorer & LSP

Test Explorer: Discovers and runs VHDL testbenches within VS Code's Testing panel.
Code Navigation: Go to Definition (F12), Find References (Shift+F12), Document Outline.
Code Generators: Port mapping autocomplete, component instantiation (from clipboard or project), and testbench/FSM templates.

4. 🤖 Model Context Protocol (MCP) Server for AI Assistants

Universal EDA Tooling for LLMs: Connects AI models (Claude, Antigravity, Cursor, Windsurf, Codex...) directly to GHDL, Yosys, and VCD simulation waveform engines.
11 Native MCP Tools: Testbench simulation, VCD waveform inspection, project-wide test runner, GHDL linting & type checks, DRC hazard & latch detection, Yosys resource estimation, FSM analysis & Mermaid diagrams, testbench scaffolding, and VHDL formatting.
Resources & Prompts: Pre-packaged hardware guidelines and AI workflows for automated testbench authoring, simulation debugging, and FSM synthesis.
One-Click Config Export: Run Questassure: Copy MCP Configuration for AI Assistants in VS Code to get instant, ready-to-paste configurations for any client.

🤖 Model Context Protocol (MCP) Setup & Architecture

What is Model Context Protocol (MCP)?

The Model Context Protocol (MCP) is an open standard developed to enable Large Language Models (LLMs) to securely access local tools, file systems, and real-time execution environments.

Rather than having an AI hallucinate VHDL simulation results or guess signal timing, the Questassure MCP Server empowers AI assistants to:

Compile and execute simulations with GHDL in real-time.
Inspect waveforms (VCD) at exact clock cycles and timestamps.
Run Design Rule Checks (DRC) to eliminate inferred latches and missing sensitivity signals.
Synthesize circuits with Yosys to estimate gate counts and flip-flops (DFF).

+-----------------------------------------------------------------------+
|                       AI Clients / IDEs                               |
|   Claude Desktop  |  Cursor  |  Antigravity  |  Windsurf  |  Copilot  |
+-----------------------------------------------------------------------+
                                  | (JSON-RPC 2.0 via stdio)
                                  v
+-----------------------------------------------------------------------+
|                    Questassure MCP Server                             |
|                    (dist/mcp-server.js)                               |
+-----------------------------------------------------------------------+
         |                       |                      |
         v                       v                      v
   GHDL Engine             Yosys Synthesis        VCD Waveform & DRC
(Simulate & Lint)        (Resource Estimate)     (Inspect & Analyze)

📦 Quick Setup for Famous AI Clients

You can generate your configuration directly inside VS Code by opening the Command Palette (Ctrl+Shift+P / Cmd+Shift+P) and selecting:

Questassure: Copy MCP Configuration for AI Assistants (Claude, Cursor, Antigravity...)

Alternatively, configure your favorite AI client manually:

1. Claude Desktop

Edit your claude_desktop_config.json:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json
Linux: ~/.config/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "questassure": {
      "command": "node",
      "args": ["/ABSOLUTE/PATH/TO/questassure-vscode/dist/mcp-server.js"]
    }
  }
}

2. Cursor IDE

Add to your project's .cursor/mcp.json or in Cursor Settings > Features > MCP:

{
  "mcpServers": {
    "questassure": {
      "command": "node",
      "args": ["/ABSOLUTE/PATH/TO/questassure-vscode/dist/mcp-server.js"]
    }
  }
}

3. Google Antigravity / Gemini Code Assist

Add to your Antigravity MCP settings or tool definitions:

{
  "mcpServers": {
    "questassure": {
      "command": "node",
      "args": ["/ABSOLUTE/PATH/TO/questassure-vscode/dist/mcp-server.js"]
    }
  }
}

4. Windsurf (Codeium)

Add to ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "questassure": {
      "command": "node",
      "args": ["/ABSOLUTE/PATH/TO/questassure-vscode/dist/mcp-server.js"]
    }
  }
}

5. Roo Code / Cline / Generic MCP Clients

{
  "name": "questassure",
  "command": "node",
  "args": ["/ABSOLUTE/PATH/TO/questassure-vscode/dist/mcp-server.js"],
  "transport": "stdio"
}

🛠️ Available MCP Tools

MCP Tool	Description
`simulate_testbench`	Compiles & runs a testbench with GHDL, returns simulation logs, assertions, and VCD path.
`inspect_waveform`	Reads a `.vcd` waveform file and returns exact signal transitions across a time window.
`run_project_tests`	Automatically discovers and executes all testbenches in the project with pass/fail summary.
`check_syntax_and_types`	Performs real-time GHDL syntax and dependency checks with line/col diagnostics.
`detect_hardware_hazards`	Runs Questassure DRC: detects inferred latches, incomplete sensitivity lists, and dead code.
`synthesize_and_estimate_resources`	Synthesizes design with Yosys, estimates DFFs, LUTs, gates, and checks synthesizability.
`get_project_hierarchy`	Returns AST & dependency map of all entities, architectures, packages, and testbenches.
`get_entity_interface`	Parses entity ports (name, direction, type), generics, and documentation headers.
`analyze_fsm`	Analyzes Finite State Machines, extracts transition matrices, and generates Mermaid diagrams.
`generate_testbench`	Generates a complete VHDL testbench scaffold with clock, reset, and stimulus template.
`format_vhdl`	Automatically formats and aligns VHDL source code according to Questassure standards.

⚙️ Settings

questassure.ghdlPath (default: "ghdl"): Path to the GHDL executable.
questassure.stopTime (default: "1us"): Default simulation stop time.
questassure.language (default: "auto"): Extension language (auto, en, fr).
questassure.openWavesOnTestExplorerRun (default: true): Auto-open waveforms on test run.

🛠️ Marketplace Installation

VS Code Marketplace: Search for Questassure VHDL and click Install.
VSIX Package: Open the Command Palette (Ctrl+Shift+P), choose Extensions: Install from VSIX..., and select your .vsix file.

📜 Credits & Requirements

GHDL: Requires system installation and binary in PATH or configured path.
Yosys: Requires system installation and binary in PATH.
Surfer: Requires system installation and binary in PATH.

Questassure VHDL

DARIER--LEGRAND Sacha