How To Build

If you just want to write MicroPython code for card10, you probably won’t need to build the firmware yourself. This page is for people who want to work on the underlying firmware itself.


  • gcc, binutils & newlib for arm-none-eabi: The packages have slightly different names on different distros.

    • Ubuntu / Debian:

      apt install gcc-arm-none-eabi binutils-arm-none-eabi libnewlib-arm-none-eabi
    • Arch:

      pacman -S arm-none-eabi-gcc arm-none-eabi-binutils arm-none-eabi-newlib
    • Fedora

      dnf install arm-none-eabi-gcc arm-none-eabi-binutils arm-none-eabi-newlib
    • macOS (Note: The card10 firmware team used Linux so far. macOS recommendations here are experimental.)

      You can use Homebrew to install the required tools. The version of the ARM crosscompiler tool chain is quite important; with the wrong version, e.g. strip and/or ld might throw strange errors.

      brew tap px4/px4
      brew install px4/px4/gcc-arm-none-eabi-63
      brew install coreutils
    • Alternative: Download ARM’s GNU toolchain. TODO

  • python3: For meson and various scripts needed for building.

  • meson (>0.43.0) & ninja: Unfortunately most distros only have very old versions of meson in their repositories. Instead, you’ll probably save yourself a lot of headaches by installing meson from pip.

    • Ubuntu / Debian:

      apt install ninja-build
      pip3 install --user meson
    • Arch (has latest meson in the repos):

      pacman -S meson
    • macOS

      brew install ninja
      pip3 install --user meson  # see - you will have to add ~/.local/bin to your PATH.
  • One of two CRC packages is required. Pick one:

    • Ubuntu / Debian / macOS

      pip3 install --user crc16


apt install python3-crcmod


pip3 install --user crcmod
  • Arch

    pacman -S python-crc16
  • python3-pillow: Python Image Library
    pip3 install --user pillow
    • Arch

      pacman -S python-pillow


Clone the master branch of the firmware repository:

$ git clone

Build Configuration

Initialize the build-system using

$ ./

Additional arguments to will be passed to meson. You can use this to for example, to enable one or more of the following optional firmware features:

  • -Ddebug_prints=true: Print more verbose debugging log messages

  • -Dble_trace=true: Enable BLE tracing. This will output lots of status info related to BLE.

  • -Ddebug_core1=true: Enable the core 1 SWD lines which are exposed on the SAO connector. Only use this if you have a debugger which is modified for core 1.


Our build-system contains a few workarounds around short-comings in meson. These workarounds might break on some setups which we did not yet test. If this is the case for you, please open an issue in our issue tracker!


Build using ninja:

$ ninja -C build/

If ninja succeeds, the resulting binaries are in build/. They are available in two formats: As an .elf which can be flashed using a debugger and as a .bin which can be loaded using the provided bootloader. Here is a list of the binaries:

  • build/bootloader/bootloader.elf: Our bootloader. It should already be on your card10. The bootloader can only be flashed using a debugger.

  • build/pycardium/pycardium_epicardium.bin: The entire firmware in one .bin.

  • build/epicardium/epicardium.elf: The core 0 part of the firmware, called Epicardium.

  • build/pycardium/pycardium.elf: Our MicroPython port, the core 1 part of the firmware.

In order to do a rebuild you can issue a clean command to ninja via

$ ninja -C build/ -t clean

Otherwise, rerunning ./ will also clean the build-directory.


macOS: If strip fails to work on the freshly compiled mpy-cross: “strip: object: (…)/lib/micropython/micropython/mpy-cross/mpy-cross malformed object (unknown load command 9)”, you a likely not using the strip that matches to your clang. Do which strip && which clang, and if the paths don’t match, clean up your PATHs, or as a quick hack, create a symlink for strip.


If you try to flash pycardium_epicardium.bin (renamed to card10.bin) and the bootloader does not finish updating, the file might be too large. ~700kB is the normal size, but problems were reported where the file size was >1MB. This was caused by the tr tool in the build process (it’s supposed to create a large file with 0xff in it) - this requires the LC_ALL environment variable to be not set, or set to “C” (but not UTF8 or similar).


Alternatively, clone the master branch of the firmware repository and enter it:

$ git clone
$ cd firmware

Afterwards, build a docker-container which will build the firmware via:

$ docker build -f docker/Dockerfile_fwbuild -t card10-firmware-builder .

Now, you can start the container with the firmware directory mounted, which will build the firmware into the firmware/build directory:

$ docker run -v $(pwd):/firmware card10-firmware-builder