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Suggested-by: fenugrec <>
Link: #103
Signed-off-by: Marc Kleine-Budde <>

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This is firmware for certain STM32F042x/STM32F072xB-based USB-CAN adapters, notably:

Of important note is that the common STM32F103 will NOT work with this firmware because its hardware cannot use both USB and CAN simultaneously. Beware also the smaller packages in the F042 series which map a USB and CAN_TX signal on the same pin and are therefore unusable !

This implements the interface of the mainline linux gs_usb kernel module and works out-of-the-box with linux distros packaging this module, e.g. Ubuntu.

Known issues

Be aware that there is a bug in the gs_usb module in linux<4.5 that can crash the kernel on device removal.

Here is a fixed version that should also work for older kernels:

The Firmware also implements WCID USB descriptors and thus can be used on recent Windows versions without installing a driver.


Building requires arm-none-eabi-gcc toolchain.

sudo apt-get install gcc-arm-none-eabi

mkdir build
cd build
cmake .. -DCMAKE_TOOLCHAIN_FILE=../cmake/gcc-arm-none-eabi-8-2019-q3-update.cmake

# or,
# cmake-gui ..
# don't forget to specify the cmake toolchain file before configuring.
# compile all targets :


# OR, each board target is a cmake option and can be disabled before running 'make';
# OR, compile a single target , e.g.
make cantact_fw

# to list possible targets :
make help

Download Binaries

Prebuild binaries can be downloded by clicking CI. On the workflow overview page, select the latest workflow that ran on master branch. The firmware artifacts can downloaded by clicking them at the bottom of the page.


Flashing candleLight on linux: (source:

  • Flashing requires the dfu-util tool. On Ubuntu, this can be installed with sudo apt install dfu-util.
  • compile as above, or download the current binary release: gsusb_cantact_8b2b2b4.bin
  • If dfu-util fails due to permission issues on Linux, you may need additional udev rules. Consult your distro's documentation and see 70-candle-usb.rules provided here.

recommended simple method

  • If compiling with cmake, make flash-<targetname_fw>, e.g. make flash-canable_fw, to invoke dfu-util.

method for reflashing a specific device by serial

  • when multiple devices are connected, dfu-util may be unable to choose which one to flash.
  • Obtain device's serial # by looking at dfu-util -l
  • adapt the following command accordingly : dfu-util -D CORRECT_FIRMWARE.bin -S "serial_number_here", -a 0 -s 0x08000000:leave
  • note, the :leave suffix above may not be supported by older builds of dfu-util and is simply a convenient way to reboot into the normal firmware.

fail-safe method (or if flashing a blank device)

  • Disconnect the USB connector from the CANtact, short the BOOT pins, then reconnect the USB connector. The device should enumerate as "STM32 BOOTLOADER".

  • invoke dfu-util manually with: sudo dfu-util --dfuse-address -d 0483:df11 -c 1 -i 0 -a 0 -s 0x08000000 -D CORRECT_FIRWARE.bin where CORRECT_FIRWARE is the name of the desired .bin.

  • Disconnect the USB connector, un-short the BOOT pins, and reconnect.

Associating persistent device names

With udev on linux, it is possible to assign a device name to a certain serial number (see udev manpages and This can be useful when multiple devices are connected at the same time.

An example configuration :

 $ cat /etc/systemd/network/ 
Property=ID_MODEL=cannette_gs_usb ID_SERIAL_SHORT="003800254250431420363230"

# from manpage:
# Note that specifying a name that the kernel might use for another interface (for example "eth0") is dangerous because the name assignment done by udev will race with the assignment done by the kernel, and only one
#   interface may use the name. Depending on the order of operations, either udev or the kernel will win, making the naming unpredictable. It is best to use some different prefix


( The serial number can be found with the lsusb utility). After reloading systemd units and resetting this board :

 $ ip a
59: cannette99: <NOARP,ECHO> mtu 16 qdisc noop state DOWN group default qlen 10

Links to related projects

  • Cangaroo open source can bus analyzer software
  • Candle.NET .NET wrapper for the candle API