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# CP210x MCP Server # cp210x-mcp
MCP server for customizing Silicon Labs CP210x USB-UART bridge devices. Allows reading and writing USB descriptor strings, power configuration, and more. 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](https://gofastmcp.com/) 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 ## Features
- List connected CP210x devices - **List and inspect** connected CP210x devices (part number, VID/PID, strings, power, lock state)
- Read/write USB product string (device name) - **Write USB descriptors** — product string, manufacturer, serial number
- Read/write manufacturer string - **Configure power** — max current draw, self-powered vs bus-powered
- Read/write serial number - **Generate udev rules** — stable `/dev/` symlinks based on product string
- Configure max power draw - **Reset device** — trigger USB re-enumeration after changes
- Set self-powered/bus-powered mode - **Lock device** — permanently freeze configuration (with strict confirmation)
- Reset device (USB re-enumeration) - **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.
- Lock device (permanent - prevents further changes)
## Requirements ## Requirements
- Linux x86_64 - Linux x86_64
- `libcp210xmanufacturing.so` - Install via AUR package or build from source - `libcp210xmanufacturing.so` — Silicon Labs CP210x manufacturing library
- Python 3.10+
- [uv](https://docs.astral.sh/uv/) (recommended)
## Installation ## Installation
### Install the library (Arch Linux) ### 1. Install the native library
**Arch Linux (AUR package included):**
```bash ```bash
cd aur/cp210xmanufacturing cd aur/cp210xmanufacturing
makepkg -si makepkg -si
``` ```
Or build from source: **From source:**
```bash ```bash
# Extract AN721SW toolkit (included in docs/)
cd AN721SW/Linux/LibrarySourcePackages/cp210xmanufacturing cd AN721SW/Linux/LibrarySourcePackages/cp210xmanufacturing
make LIB_ARCH=64 make LIB_ARCH=64
sudo make install sudo make install
sudo ldconfig sudo ldconfig
``` ```
### Install the MCP server 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
```bash ```bash
# With uv (recommended)
uv tool install . uv tool install .
# Or with pip
pip install .
``` ```
## Usage ### 3. Add to Claude Code
### Add to Claude Code
```bash ```bash
claude mcp add cp210x -- uvx cp210x-mcp claude mcp add cp210x -- uvx cp210x-mcp
``` ```
### Available Tools Or for development (runs from source):
```bash
claude mcp add cp210x-local -- uv run --directory /path/to/cp2102-uart cp210x-mcp
```
## Tools
| Tool | Description | | Tool | Description |
|------|-------------| |------|-------------|
| `list_devices` | List connected CP210x devices | | `list_devices` | List connected CP210x devices with description and serial |
| `get_device_info` | Get detailed device information | | `get_device_info` | Full device details — part number, VID/PID, strings, power, lock state |
| `set_product_string` | Set USB product string (device name) | | `set_product_string` | Write USB product string (max 126 chars) |
| `set_manufacturer_string` | Set USB manufacturer string | | `set_manufacturer_string` | Write USB manufacturer string (max 45 chars) |
| `set_serial_number` | Set USB serial number | | `set_serial_number` | Write USB serial number (max 63 chars) |
| `set_max_power` | Set max USB power draw (mA) | | `set_max_power` | Set max USB power draw in mA (0–500, rounded to nearest 2) |
| `set_self_powered` | Set self-powered vs bus-powered | | `set_self_powered` | Toggle self-powered vs bus-powered reporting |
| `reset_device` | Reset device (USB re-enumeration) | | `reset_device` | USB disconnect/reconnect to apply changes |
| `lock_device` | PERMANENTLY lock device config | | `lock_device` | **Permanently** freeze device configuration |
| `setup_udev_rule` | Generate and install a udev rule for a stable `/dev/` symlink |
### Example ## Architecture
```bash ```
# In Claude Code conversation: Claude Code ──stdio──▶ FastMCP server (server.py)
> What CP210x devices are connected? │
> Change the product name of device 0 to "My Custom Device" ▼
Python ctypes (bindings.py)
│
▼
libcp210xmanufacturing.so
│
▼
libusb ──▶ CP210x device
``` ```
## Relationship to mcserial 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.
This MCP server complements [mcserial](https://github.com/ryanmalloy/mcserial) which handles serial port communication. Use this server for **device customization** (changing USB descriptors) and mcserial for **serial communication** (sending/receiving data over UART). ### 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](https://github.com/ryanmalloy/mcserial).
## Reference
- [CP2102 Datasheet](https://www.silabs.com/documents/public/data-sheets/CP2102-9.pdf)
- [AN721: Device Customization Guide](https://www.silabs.com/documents/public/example-code/AN721SW.zip) — source for `libcp210xmanufacturing`
- [AN197: Serial Communication Guide](https://www.silabs.com/documents/public/application-notes/an197-serial-communications-guide-cp210x.pdf)
## License ## License