Bns Lang

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Write PLC ladder logic with just a numpad.

A minimal DSL that compiles to IEC 61131-3 ladder diagrams. No IDE needed. No mouse clicking. Just type numbers → get rungs.

Quick Start · Syntax · Examples · Why? · Roadmap

⚡ 3 Seconds to Understand

Traditional PLC programming requires a GUI IDE, mouse-clicking contacts onto rungs, and navigating nested menus. BNS Lang lets you type it.

         BNS Lang                          Ladder Diagram
                                     
    1 2 + 3 = 50                     ──┤ X1 ├──┤ X2 ├──┬──┤ X3 ├──── ( Y50 )
                                                        │
    1 2 | 4 = 50                     ──┤ X1 ├──┤ X2 ├──┤ X4 ├────── ( Y50 )

That's it. Numbers are I/O addresses. + is series (AND). | is parallel (OR). = is the output coil.

🚀 Quick Start

# Install
npm install -g bns-lang

# Compile a .bns file to IEC 61131-3 structured text
bns compile program.bns -o output.st

# Or pipe directly
echo "1 2 + 3 = 50" | bns compile --stdout

Create program.bns:

# Motor start/stop circuit
# START(X1) AND NOT STOP(X2) OR HOLDING(Y10) → MOTOR(Y10)
# Contact 110 = Y10 (output as contact), coil 10 = Y10

1 -2 | 110 = 10

Compile:

$ bns compile program.bns --stdout

(* Generated by BNS Lang v2.0 *)
(* Motor start/stop circuit *)

PROGRAM MAIN
VAR
  X1 AT %IX0.1 : BOOL;
  X2 AT %IX0.2 : BOOL;
  Y10 AT %QX1.10 : BOOL;
END_VAR

Y10 := ((X1 AND NOT X2) OR Y10);

END_PROGRAM

📖 Syntax

BNS Lang is designed to be typed entirely on a numpad + a few keys. The full grammar fits on a sticky note.

Contacts & Coils

Operators

Special

Address Mapping

Address mapping is configurable per target PLC. Defaults match LS Electric XGT conventions.

📝 Examples

See the examples/ folder: 01-basics.bns, 02-self-holding.bns, 03-conveyor.bns, 04-traffic-light.bns, 05-wafer-transfer.bns.

🤔 Why BNS Lang?

• One line. 8 characters. Zero clicks. for X1 AND X2 → Y50: 1 2 = 50
• Version control with Git. Review in PRs. Generate from scripts. Pipe through CI/CD.
• For PLC engineers, automation teams, educators, and AI/LLM developers.

🤖 AI Integration (Cursor / Claude Code)

BNS Lang is the first PLC language designed for AI-native development. Two ways to use it:

Option 1: Cursor Rules (zero setup)

This repo includes .cursorrules — just open the project in Cursor and start talking:

You: "컨베이어에 센서 감지되면 모터 돌리고 비상정지 누르면 멈추게 해줘"

Cursor: Here's the BNS Lang code:

# Conveyor motor control
# X1 = Sensor, X99 = E-Stop (NC), Y100 = Motor
1 -99 | 200 = 100    # Sensor AND NOT E-Stop, self-held (200 = M200)
99 =/ 100            # E-Stop resets motor

Works with any natural language → BNS Lang → IEC 61131-3 pipeline.

Option 2: MCP Server (full pipeline)

Connect BNS Lang as an MCP tool in Cursor or Claude Code:

Cursor — .cursor/mcp.json is included:

{
  "mcpServers": {
    "bns-lang": {
      "command": "node",
      "args": ["./src/mcp-server.js"]
    }
  }
}

Claude Code:

claude mcp add bns-lang node ./src/mcp-server.js

Now you get 4 tools directly in your AI coding assistant:

Full workflow in Cursor/Claude Code:

You: "Create a traffic light controller with 3 phases"
AI:  [generates BNS code]
AI:  [calls bns_check → validates]
AI:  [calls bns_compile → outputs ST]
AI:  [calls bns_ladder → shows diagram]
You: "Change green phase to 7 seconds"
AI:  [modifies and recompiles]

Natural language → BNS Lang → Compile → Verify → Ladder diagram, all without leaving your editor.

🏗️ Architecture

  .bns source          Parser          IR            Code Generator       Target
 ┌──────────┐    ┌──────────────┐   ┌─────┐    ┌────────────────────┐   ┌──────────┐
 │ 1 2 = 50 │ →  │ Tokenizer →  │ → │ AST │ →  │ LS Electric XGT ST │ → │ .st file │
 └──────────┘    │ Parser       │   │     │    │ IEC 61131-3 ST     │   │ .prj     │
                 └──────────────┘   │     │    │ Ladder JSON (viz)  │   └──────────┘
                                    └─────┘    └────────────────────┘

Target PLCs

🛠️ CLI Reference

# Compile to structured text
bns compile input.bns -o output.st

# Compile with target PLC
bns compile input.bns --target xgt -o output.st
bns compile input.bns --target inovance -o output.prj

# Validate syntax only
bns check input.bns

# Output AST as JSON (for tooling/LLM integration)
bns ast input.bns --json

# Output ladder diagram as ASCII art  
bns ladder input.bns

# REPL mode
bns repl
> 1 2 = 50
──┤ X1 ├──┤ X2 ├──( Y50 )
>

📦 Project Structure

bns-lang/
├── .cursor/
│   └── mcp.json           # Cursor MCP config (ready to use)
├── .cursorrules            # Cursor AI rules for BNS Lang generation
├── .github/
│   ├── workflows/ci.yml
│   ├── FUNDING.yml
│   └── ISSUE_TEMPLATE/
├── src/
│   ├── tokenizer.js
│   ├── parser.js
│   ├── ir.js
│   ├── generators/ (st.js, xgt.js, inovance.js, ladder-json.js, ascii.js)
│   ├── mcp-server.js       # MCP server for Cursor / Claude Code
│   ├── cli.js
│   └── index.js
├── examples/
├── docs/ (SYNTAX.md, TARGETS.md, LLM-GUIDE.md)
├── tests/
├── package.json
├── LICENSE
└── README.md

🗺️ Roadmap

• Core parser & tokenizer
• IEC 61131-3 Structured Text output
• LS Electric XGT target
• ASCII ladder diagram output
• CLI tool
• Timer/Counter support
• Cursor Rules (.cursorrules)
• MCP Server (Cursor / Claude Code integration)
• Inovance H5U/H3U target (beta)
• Siemens S7 SCL target
• Function Block (FB) support
• bns fmt — auto-formatter
• bns sim — offline logic simulator
• VS Code extension with syntax highlighting
• Web playground (try BNS Lang in browser)
• PLAIDE deep integration

🤝 Contributing

Contributions are welcome! See CONTRIBUTING.md for guidelines.

git clone https://github.com/BAESY2/bns-lang.git
cd bns-lang
npm install
npm test

Good First Issues

• Add syntax highlighting for more editors
• Write examples for common PLC patterns
• Add a new target PLC code generator
• Improve error messages

📄 License

MIT — Use it in your commercial PLC projects. No strings attached.

BNS Lang is part of the ZENION industrial automation ecosystem.

Industrial automation deserves modern developer tooling.