MCP Server for Segger RTT via J-Link

An MCP server that provides access to Segger RTT (Real Time Transfer) through a J-Link debugger. This allows an LLM (like Claude) to interact with embedded devices by reading and writing RTT data.

Features

• RTT Read: Read output from embedded devices through RTT up-buffer
• RTT Write: Send commands to embedded devices through RTT down-buffer
• J-Link Management: Connect/disconnect J-Link debuggers, list available devices
• Real-time Display: RTT data is continuously printed to terminal while monitoring
• Ring Buffer: Recent RTT data is accumulated for reading by the LLM

Prerequisites

• Python 3.10+
• SEGGER J-Link Software installed (provides JLinkARM.dll/libjlinkarm.so)
• A J-Link compatible debugger
• Target device running SEGGER RTT

Installation

# Clone or navigate to this directory
cd mcp-rtt-server

# Install dependencies
pip install -e .

Usage

Step 1: 安装

cd mcp-rtt-server
pip install -e .

Step 2: 启动 MCP Inspector（调试/测试用）

终端 A — 启动 MCP 服务器：

npx @modelcontextprotocol/inspector python -m mcp_rtt_server.server

启动后会输出一个本地网址（如 http://localhost:6274/?...），在浏览器打开。

终端 B — 实时查看 RTT 数据：

# PowerShell
Get-Content .\rtt_output.log -Wait

# Git Bash / WSL
tail -f ./rtt_output.log

Step 3: 使用工具

在浏览器 Inspector 中按顺序调用：

1. jlink_connect — 连接 J-Link 和目标设备，启动 RTT 监控
2. rtt_read — 读取设备发送的 RTT 数据
3. rtt_write — 向设备发送数据（需固件支持接收）
4. jlink_status — 查看连接状态和缓冲区信息
5. jlink_disconnect — 断开连接

Claude Code 集成

在项目 .claude/settings.json 中添加：

{
  "mcpServers": {
    "rtt": {
      "command": "python",
      "args": ["-m", "mcp_rtt_server.server"],
      "cwd": "."
    }
  }
}

注意：将 python 替换为你的 Python 解释器实际路径（如 C:\Python313\python.exe）。

重启 Claude Code 会话后，可直接用自然语言与设备交互，例如：

• "连接 RTT 读取设备数据"
• "查看设备状态"

Claude Desktop 集成

编辑 %APPDATA%\Claude\claude_desktop_config.json：

{
  "mcpServers": {
    "rtt": {
      "command": "python",
      "args": ["-m", "mcp_rtt_server.server"],
      "cwd": "."
    }
  }
}

注意：cwd 需要改为本项目的实际绝对路径，因为 Claude Desktop 不会自动定位到项目目录。

Available Tools

Tool	Description
jlink_connect	Connect to J-Link and start RTT monitoring
jlink_disconnect	Disconnect from J-Link
jlink_status	Get connection status and buffer info
rtt_list_devices	List available J-Link devices
rtt_read	Read accumulated RTT data
rtt_write	Write data to RTT down-buffer
rtt_clear	Clear the RTT ring buffer

Example Session

> jlink_connect(device="HC32L19x")
Connected to J-Link device 'HC32L19x' (serial: 12345678, speed: 4000 kHz)
RTT monitoring started on channel 0

> rtt_read()
[OSAL] HC32L19x OSAL starting...
[RTT] SEGGER RTT initialized
[OSAL] Registering tasks...
[OSAL] Starting scheduler...

> rtt_write(channel=0, data="status\r\n")
Wrote 7 bytes to RTT channel 0

Architecture

┌─────────────────┐     stdio (JSON-RPC)     ┌─────────────────┐
│   Claude /      │ ◄──────────────────────►  │  MCP RTT Server │
│   MCP Client    │                          │    (Python)     │
└─────────────────┘                          └────────┬────────┘
                                                      │
                                             pylink   │
                                                      ▼
                                            ┌─────────────────┐
                                            │  JLinkARM.dll   │
                                            └────────┬────────┘
                                                      │ USB
                                                      ▼
                                            ┌─────────────────┐
                                            │   J-Link Probe  │
                                            └────────┬────────┘
                                                      │ SWD/JTAG
                                                      ▼
                                            ┌─────────────────┐
                                            │  Target Device  │
                                            │  (HC32L19x)     │
                                            │  SEGGER RTT     │
                                            └─────────────────┘

Environment Variables

Variable	Default	Description
JLINK_SERIAL	(none)	J-Link serial number
JLINK_DEVICE	HC32L19x	Target device name
JLINK_SPEED	4000	SWD speed in kHz
RTT_CHANNEL	0	Default RTT channel
RTT_RING_BUFFER_SIZE	100	Ring buffer entries
RTT_POLL_INTERVAL_MS	10	Poll interval in ms

Troubleshooting

"J-Link not found"

• Make sure J-Link software is installed
• Check that J-Link is connected via USB
• Try running as administrator/root

"Device not supported"

• Check if the device name is correct
• Try using rtt_list_devices to see available probes
• Verify the target is connected and powered

"RTT not initialized"

• Make sure the target firmware calls SEGGER_RTT_Init()
• Check that RTT buffers are configured in SEGGER_RTT_Conf.h

License

MIT