130 lines
5.1 KiB
Markdown
130 lines
5.1 KiB
Markdown
# cp210x-mcp
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MCP server for customizing Silicon Labs CP210x USB-UART bridge devices. Read and write USB descriptor strings, power configuration, and device lock state — all through natural language in Claude Code.
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Built on [FastMCP](https://gofastmcp.com/) and Silicon Labs' `libcp210xmanufacturing` native library via Python ctypes.
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## Why
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CP210x chips (CP2102, CP2102N, CP2104, etc.) store USB descriptor strings in one-time-programmable EPROM. Silicon Labs provides a GUI tool and a C library for customization, but both are clunky to use — especially when managing multiple identical devices that need unique identifiers.
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This MCP server lets you customize devices conversationally:
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```
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> What CP210x devices are connected?
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> Change the product string of device 0 to "RYLR998 0033001104645C0B00001130"
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> Set up a udev rule so it always appears at /dev/rylr998-1130
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```
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## Features
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- **List and inspect** connected CP210x devices (part number, VID/PID, strings, power, lock state)
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- **Write USB descriptors** — product string, manufacturer, serial number
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- **Configure power** — max current draw, self-powered vs bus-powered
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- **Generate udev rules** — stable `/dev/` symlinks based on product string
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- **Reset device** — trigger USB re-enumeration after changes
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- **Lock device** — permanently freeze configuration (with strict confirmation)
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- **Elicitation support** — write operations request confirmation when the MCP client supports it; graceful fallback otherwise. Lock is the exception: it *requires* explicit confirmation and will refuse if elicitation is unavailable.
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## Requirements
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- Linux x86_64
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- `libcp210xmanufacturing.so` — Silicon Labs CP210x manufacturing library
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- Python 3.10+
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- [uv](https://docs.astral.sh/uv/) (recommended)
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## Installation
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### 1. Install the native library
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**Arch Linux (AUR package included):**
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```bash
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cd aur/cp210xmanufacturing
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makepkg -si
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```
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**From source:**
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```bash
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# Extract AN721SW toolkit (included in docs/)
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cd AN721SW/Linux/LibrarySourcePackages/cp210xmanufacturing
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make LIB_ARCH=64
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sudo make install
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sudo ldconfig
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```
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The library installs to `/usr/lib/libcp210xmanufacturing.so` and uses libusb to communicate with devices. You'll need udev rules for non-root access — the AUR package installs these automatically, or copy `aur/cp210xmanufacturing/SiliconLabs.rules` to `/usr/lib/udev/rules.d/`.
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### 2. Install the MCP server
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```bash
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uv tool install .
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```
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### 3. Add to Claude Code
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```bash
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claude mcp add cp210x -- uvx cp210x-mcp
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```
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Or for development (runs from source):
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```bash
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claude mcp add cp210x-local -- uv run --directory /path/to/cp2102-uart cp210x-mcp
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```
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## Tools
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| Tool | Description |
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|------|-------------|
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| `list_devices` | List connected CP210x devices with description and serial |
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| `get_device_info` | Full device details — part number, VID/PID, strings, power, lock state |
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| `set_product_string` | Write USB product string (max 126 chars) |
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| `set_manufacturer_string` | Write USB manufacturer string (max 45 chars) |
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| `set_serial_number` | Write USB serial number (max 63 chars) |
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| `set_max_power` | Set max USB power draw in mA (0–500, rounded to nearest 2) |
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| `set_self_powered` | Toggle self-powered vs bus-powered reporting |
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| `reset_device` | USB disconnect/reconnect to apply changes |
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| `lock_device` | **Permanently** freeze device configuration |
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| `setup_udev_rule` | Generate and install a udev rule for a stable `/dev/` symlink |
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## Architecture
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```
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Claude Code ──stdio──▶ FastMCP server (server.py)
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│
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▼
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Python ctypes (bindings.py)
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│
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▼
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libcp210xmanufacturing.so
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│
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▼
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libusb ──▶ CP210x device
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```
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The native library uses **libusb** for device access, which is separate from the kernel's `cp210x` serial driver. Both can coexist — you can read/write UART data over `/dev/ttyUSB0` while simultaneously customizing USB descriptors through this server.
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### Safety model
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CP210x EPROM writes are one-time-programmable with limited write cycles. The server uses a tiered confirmation model:
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- **Reads** — no confirmation needed
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- **Writes** (strings, power) — requests confirmation via MCP elicitation; falls back to proceeding if the client doesn't support it
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- **Lock** — *always* requires elicitation; hard-refuses without it
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## Complementary tools
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This server handles **device customization** (USB descriptors, power config). For **serial communication** (sending/receiving data over UART), use [mcserial](https://github.com/ryanmalloy/mcserial).
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## Reference
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- [CP2102 Datasheet](https://www.silabs.com/documents/public/data-sheets/CP2102-9.pdf)
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- [AN721: Device Customization Guide](https://www.silabs.com/documents/public/example-code/AN721SW.zip) — source for `libcp210xmanufacturing`
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- [AN197: Serial Communication Guide](https://www.silabs.com/documents/public/application-notes/an197-serial-communications-guide-cp210x.pdf)
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## License
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MIT
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