USB LIN Converter MCP server

USB LIN Converter (uLC)

Open source USB ↔ LIN bus dongle. LIN 2.1 master, slave or monitor. SLCAN-compatible virtual COM port - works on Windows, Linux and macOS with no proprietary drivers.

The USB LIN Converter (uLC) is a small open-source USB dongle (STM32F042C6, ~31 × 18 mm) that lets a PC act as a LIN bus master, slave or passive monitor. It enumerates as a USB CDC virtual COM port and speaks an SLCAN-style ASCII protocol, so it bridges into Linux SocketCAN via slcand and works with parts of can-utils.

A commercial automotive LIN analyzer typically costs hundreds to thousands of euros. This one is around $27 on Tindie.

The LIN protocol implementation is based on openLIN.

Features

• LIN 2.1 support
• Monitor mode - full frame reception plus single-frame transmission
• Master mode - up to 15 scheduled frame slots
• Slave mode - up to 15 scheduled frame slots for slave simulation
• 9600 / 19200 baud rate selection
• Optical isolation between LIN and the USB / PC side
• Software-controlled termination resistors
• External 4.5 - 28 V powers the LIN transceiver
• Device size 31 × 18 mm (without USB connector)
• USB DFU bootloader for firmware updates
• No proprietary drivers - Linux / macOS / Windows
• MCP server so AI agents can sniff and reverse-engineer a LIN bus (see below)

Where to buy

Quickstart

1. Plug the device into a USB port. It enumerates as a virtual COM port (COM3 on Windows, /dev/ttyACM0 on Linux, /dev/cu.usbmodem* on macOS).
2. On Windows, install the ST Virtual COM Port driver. On Linux and macOS no driver is required.
3. Open the port at any baud rate (USB CDC ignores baud). Line ending must be CR (0x0D).
4. Power the LIN side with 4.5 - 28 V on the external supply pin.
5. Send S0 to select 19200 baud, then l to enter monitor mode. Bus traffic will start to appear.

Linux SocketCAN bridge

sudo slcand -o -s8 -t hw -S 921600 /dev/ttyACM0 slcan0
sudo ip link set slcan0 up
candump slcan0

Python (pyserial) sniff snippet

import serial
ser = serial.Serial('/dev/ttyACM0', timeout=1)
ser.write(b'S0\r')   # 19200 baud
ser.write(b'l\r')    # monitor mode
while True:
    line = ser.readline()
    if line:
        print(line.decode(errors='replace').strip())

A higher-level Python library is provided in python_lib/ (package ucanlintools).

AI agents (MCP server)

pythonlib/ucanlintools/mcpserver.py is an MCP server that lets an AI agent sniff and reverse-engineer a LIN bus: capture traffic with per-id periods and changing bits, log every data change while you press a button, find the bus speed and checksum type automatically, and decode or encode signals from an LDF file. It is read-only by default; sending frames and acting as master or slave needs --allow-transmit.

Shortened. The full README is on GitHub.