Caution

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND. BY USING IT YOU TAKE ALL THE RISKS FOR YOUR ACTIONS

Rinkhals

Rinkhals is a custom firmware for the Anycubic Kobra 3 3D printer. The goal of this project is to create a simple and safe overlay for the Kobra 3 firmware, adding some usefule features. Multiple versions can be installed at the same time and it can easily be disabled.

Here is a list of the features I added:

• Mainsail, Fluidd and Moonraker (using nginx)
• USB camera support through Fluidd and Moonraker (mjpg-streamer)
• Print from Moonraker will show the print screen (moonraker-proxy)
• Access using SSH and ADB

This project is named after rinkhals. They are a sub-species of Cobras ... Kobra 3 ... Rinkhals 👏

The stock firmwares are available on a separate branch: https://github.com/jbatonnet/Rinkhals/tree/stock-firmwares

Known issues / Future developments

• If not installed properly, the printer shows a 11407 error > See the section about error 11407 below
• The camera is not accessible from Anycubic apps anymore
• Mainsail/Fluidd gcode preview doesn't work
• OctoApp notification plugin is missing

Other:

• Build the SWU file and make sure SSH works all the way
• Check free space before install
• Buildroot / FFmpeg with freetext, mjpeg, fbdev, png, bmp, h264
• Installation screen (kill K3SysUi, show screens then reboot or restore K3SysUi?)
• Reimplement gkcam
• Timelapse support
• Logs cleanup
• Old Rinkhals versions cleanup
• Packaging + Auto version names + Github actions

How to install a firmware

At this point you should have a .swu file, either a stock firmware or a custom one.

• Format a USB drive as FAT32
• Create a new directory
  • If the firmware is based on 2.3.3.9 or later (most firmwares should now), name it aGVscF9zb3Nf
  • If it's an older one before 2.3.3.9, name it update
• Copy your .swu file in this directory as update.swu
• Plug the USB drive in the Kobra 3
• You should hear a beep, meaning the printer detected the firmware file
• Give the printer some time
• Then it should reboot itself. If it doesn't, wait 20~30 minutes then reboot the printer manually
• Once installed, the update.swu file will have been removed from the USB drive, you can check as a confirmation

Note

When installing Rinkhals, you will ear one beep, then ~10s later a progress will show up on screen.
Once you ear two beeps or when the progress bar is full green, the installation is complete and the printer will reboot.
If you ear 3 beeps or the progress bar is full red, the installation failed but everything should still work. You will find the installation logs on the USB drive.

My printer shows a 11407 error

Don't worry, you can still re-flash stock firmware and try again. Here is the full process to recover from this state:

• Reflash the stock 2.3.3.9 firmware (https://github.com/jbatonnet/Rinkhals/tree/stock-firmwares)
• Do a factory reset from the printer touchscreen (Settings > Device information > System restore)
• Once done, let the printer update itself to 2.3.5.3 or flash the stock 2.3.5.3 firmware
• Then perform the regular installation described above

Note

Even if you get 11407 using a 2.5.3.5 firmware, you might need to downgrade to 2.3.3.9 to recover. Please follow all the steps listed above

Repo structure

• doc/: Some documentation I gathered on my journey
• build/: The tools, scripts and Dockerfiles needed to build this project
  • 1-buildroot/: Buildroot setup to build the base filesystem / binaries
  • 2-external/: Scripts to get the external components like Fluidd and Mainsail
  • 3-python/: Dockerfile and script to build and get the necessary Python packages
• files/: The target filesystem overlay and the scripts needed to run the firmware
  • 1-buildroot/: First layer containing Buildroot built binaries
  • 2-external/: External components layer for Fluidd, Mainsail, Moonraker and OctoApp
  • 3-python/: Layer with all the necessary Python packages
  • 4-rinkhals/: Fimware config and scripts to run Rinkhals

Firmware startup

During this custom firmware installation, update.sh will install the overlay filesystem in /useremain/rinkhals. Every version you install will end up in a different directory, allowing you to easily switch between versions or rollback if something goes wrong.

Then start.sh.patch if appended at the end of the default startup scripts. Its goal is to check Rinkhals installation with minimal modification and run start-rinkhals.sh.

start-rinkhals.sh will now check for the requested version in /useremain/rinkhals/.version, check for a .disable-rinkhals file on a USB drive if needed and then run the actual Rinkhals loader for the selected version.

Development

If you want to fully build this firmware yourself and avoid using the prebuilt binaries, you will need to do the following:

• Layer 1: Buildroot (files/1-buildroot)

  • Build and run build/buildroot/Dockerfile or start your own instance
    • Some run examples are provider in the Dockerfile
  • Use the build/buildroot/.config Buildroot configuration file to build the base filesystem binaries
  • Use build/buildroot/build-target.sh to filter and extract the files in /output

• Layer 2: External apps (files/2-external)

  • Update git submodules
  • Build files/2-external/Dockerfile if you want
  • docker run --rm -it -v .\build:/build -v .\files:/files ghcr.io/jbatonnet/rinkjals/build /build/2-external/get-external.sh

• Layer 3: Python packages for Moonraker (files/3-python)

  • Build files/3-python/Dockerfile if you want
  • docker run --privileged --rm tonistiigi/binfmt --install all
  • docker run --rm -it -v .\build:/build -v .\files:/files ghcr.io/jbatonnet/rinkjals/python /build/3-python/copy-output.sh

If you want to quickly iterate on development, a quick deployment method is provided:

• To synchronize your copy of Rinkhals on the printer, run docker run --rm -it -e KOBRA_IP=x.x.x.x -v .\build:/build -v .\files:/files --entrypoint=/bin/sh rclone/rclone:1.68.2 /build/deploy-dev.sh
• On the printer, update /useremain/rinkhals/.version to dev
• On the printer, run /useremain/rinkhals/start-rinkhals.sh to manually start Rinkhals

Thanks

Thanks to the following projects/persons:

• utkabobr (https://github.com/utkabobr/DuckPro-Kobra3)
• systemik (https://github.com/systemik/Kobra3-Firmware/blob/main/update-preparation/cfw/scripts/led-on.sh)
• Icon created by Freepik - Flaticon (https://www.flaticon.com/free-icons/snake)