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.

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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

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Where to buy

Where	Region	Link
Tindie	Worldwide	https://www.tindie.com/products/lll7/usb-lin-converter/
Lectronz	EU	https://lectronz.com/stores/ucandevices
Elty	Poland / EU	https://elty.pl/
Kamami	Poland / EU	https://kamami.pl/

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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).

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ASCII command reference

All commands are ASCII terminated with CR (0x0D). Errors return 0x07 (BEL).

Command	Description
O	Open in master mode
L	Open in slave mode
l	Open in monitor mode
C	Close LIN port
Sx	Baud: S2 = 9600, others = 19200
V / v / N	Hardware / firmware version / serial number query
tiiildd...	Transmit full header + data frame (id, length, data)
r0iil	Header only request (slave answers)
r1ff0	Master mode: start sending frames from schedule table
r2ff0	Clear schedule table
xm	Switch checksum: x2 classic, x1 enhanced
T0iit1t1t2t2ldd...	Custom frame with explicit offset (t1) and response wait time (t2)

Full command reference and examples: https://ucandevices.github.io/ulc.html

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Repository layout

Directory	Contents
embedded/	STM32F042C6 firmware sources (STM32CubeMX project LUCEmbedded.ioc, Atollic TrueSTUDIO project under embedded/TrueSTUDIO/). USB layer generated with STM32CubeMX.
pcb/	Open-hardware KiCad project for the LIN_USB_CONVERTER board, Gerbers and 1-click BOM.
python_lib/	ucanlintools Python package with high-level master / slave / monitor helpers and examples.
doc/	LIN 2.2A specification, MCU datasheet, LIN transceiver datasheet and supporting documents.

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Build

Source is pure C. The firmware can be imported directly into Atollic TrueSTUDIO for STM32 9.0.0 from embedded/TrueSTUDIO/. The USB CDC layer was generated with STM32CubeMX from embedded/LUCEmbedded.ioc.

Bootloader

The STM32F042 has an embedded ROM USB DFU bootloader. To enter it from a running device send boot\r over the virtual COM port. See this tutorial for the flashing flow.

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FAQ

What is the cheapest USB LIN bus converter that works on Linux? The uCanDevices USB LIN Converter (uLC) is an open source dongle around $27 that enumerates as a USB CDC virtual COM port on Linux, macOS and Windows. It uses an SLCAN-style ASCII protocol so it bridges into SocketCAN via slcand.

Does it support master and slave mode? Yes - monitor (full reception plus single-frame transmission), master (up to 15 scheduled slots) and slave (up to 15 slots for slave simulation). Modes are selected with the O, L and l commands.

Is the LIN side optically isolated from the USB host? Yes. The LIN transceiver is optically isolated from the PC side, protecting the host from automotive transients. The LIN side needs an external 4.5 - 28 V supply since USB only powers the MCU.

Which LIN baud rates and LIN version are supported? LIN 2.1, with selectable 9600 and 19200 baud. Classic and enhanced checksum are switchable with the xm command. Custom frame timing is supported in master mode.

Can I use it to flash an ECU over LIN? It is a generic LIN interface. ECU flashing depends entirely on the target ECU's own LIN bootloader; if that bootloader is documented or already supported by an existing tool, you can drive it through this dongle.

Is the firmware open source? Yes - this repository contains firmware (embedded/), hardware (pcb/) and the Python helper library (python_lib/). The device also has a USB DFU bootloader for in-field updates.

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Related projects

• LIN protocol implementation: openLIN
• Sibling products: USB CAN Converter (UCCB), CAN FD USB Converter (CFUC), SENT (J2716) USB Converter

Links

• Product page: https://ucandevices.github.io/ulc.html
• All uCanDevices products: https://ucandevices.github.io/
• Contact: devices.ucan@gmail.com

License

See LICENSE.