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cp210x-mcp

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.

Built on FastMCP and Silicon Labs' libcp210xmanufacturing native library via Python ctypes.

Why

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.

This MCP server lets you customize devices conversationally:

> What CP210x devices are connected?
> Change the product string of device 0 to "RYLR998 0033001104645C0B00001130"
> Set up a udev rule so it always appears at /dev/rylr998-1130

Features

  • List and inspect connected CP210x devices (part number, VID/PID, strings, power, lock state)
  • Write USB descriptors — product string, manufacturer, serial number
  • Configure power — max current draw, self-powered vs bus-powered
  • Generate udev rules — stable /dev/ symlinks based on product string
  • Reset device — trigger USB re-enumeration after changes
  • Lock device — permanently freeze configuration (with strict confirmation)
  • 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.

Requirements

  • Linux x86_64
  • libcp210xmanufacturing.so — Silicon Labs CP210x manufacturing library
  • Python 3.10+
  • uv (recommended)

Installation

1. Install the native library

Arch Linux (AUR package included):

cd aur/cp210xmanufacturing
makepkg -si

From source:

# Extract AN721SW toolkit (included in docs/)
cd AN721SW/Linux/LibrarySourcePackages/cp210xmanufacturing
make LIB_ARCH=64
sudo make install
sudo ldconfig

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/.

2. Install the MCP server

uv tool install .

3. Add to Claude Code

claude mcp add cp210x -- uvx cp210x-mcp

Or for development (runs from source):

claude mcp add cp210x-local -- uv run --directory /path/to/cp2102-uart cp210x-mcp

Tools

Tool Description
list_devices List connected CP210x devices with description and serial
get_device_info Full device details — part number, VID/PID, strings, power, lock state
set_product_string Write USB product string (max 126 chars)
set_manufacturer_string Write USB manufacturer string (max 45 chars)
set_serial_number Write USB serial number (max 63 chars)
set_max_power Set max USB power draw in mA (0–500, rounded to nearest 2)
set_self_powered Toggle self-powered vs bus-powered reporting
reset_device USB disconnect/reconnect to apply changes
lock_device Permanently freeze device configuration
setup_udev_rule Generate and install a udev rule for a stable /dev/ symlink

Architecture

Claude Code ──stdio──▶ FastMCP server (server.py)
                              │
                              ▼
                        Python ctypes (bindings.py)
                              │
                              ▼
                    libcp210xmanufacturing.so
                              │
                              ▼
                          libusb ──▶ CP210x device

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.

Safety model

CP210x EPROM writes are one-time-programmable with limited write cycles. The server uses a tiered confirmation model:

  • Reads — no confirmation needed
  • Writes (strings, power) — requests confirmation via MCP elicitation; falls back to proceeding if the client doesn't support it
  • Lock — always requires elicitation; hard-refuses without it

Complementary tools

This server handles device customization (USB descriptors, power config). For serial communication (sending/receiving data over UART), use mcserial.

Reference

License

MIT