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Prusa Firmware MK3

This repository contains the source code and the development versions of the firmware running on the Original Prusa i3 MK3S/MK3/MK2.5S/MK2.5 line of printers.

The latest official builds can be downloaded from Prusa Drivers. Pre-built development releases are also available here.

The firmware for the Original Prusa i3 printers is proudly based on Marlin 1.0.x by Scott Lahteine (@thinkyhead) et al. and is distributed under the terms of the GNU GPL 3 license.

This repository contains development material only!



There are two ways to build Prusa-Firmware on Linux: using CMake (recommended for developers) or with PF-build which is more user-friendly for casual users.



The workflow should be pretty straightforward for anyone with development experience. After installing git and a recent version of python 3 all you have to do is:

# clone the repository
git clone
cd Prusa-Firmware

# automatically setup dependencies

# configure and build
mkdir build
cd build
cmake .. -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=../cmake/AvrGcc.cmake

Detailed CMake guide

Building with cmake requires:

  • cmake >= 3.22.5
  • ninja >= 1.10.2 (optional, but recommended)

Python >= 3.6 is also required with the following modules:

  • pyelftools (package python3-pyelftools)
  • polib (package python3-polib)
  • regex (package python3-regex)

Additionally gettext is required for translators.

Assuming a recent Debian/Ubuntu distribution, install the dependencies globally with:

sudo apt-get install cmake ninja python3-pyelftools python3-polib python3-regex gettext

Prusa-Firmware depends on a pinned version of avr-gcc and the external prusa3dboards package. These can be setup using ./utils/

# automatically setup dependencies

which will download and unpack them inside the .dependencies directory. ./utils/ will also install cmake, ninja and the required python packages if missing, although installing those through the system's package manager is usually preferred.

You can then proceed by creating a build directory, configure for AVR and build:

# configure
mkdir build
cd build
cmake .. -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=../cmake/AvrGcc.cmake

# build

By default all variants are built. There are several ways to restrict the build for development. During configuration you can set:

  • cmake -DFW_VARIANTS=variant: comma-separated list of variants to build. This is the file name as present in Firmware/variants without the final .h.
  • cmake -DMAIN_LANGUAGES=languages: comma-separated list of ISO language codes to include as main translations.
  • cmake -DCOMMUNITY_LANGUAGES=languages: comma-separated list of ISO language codes to include as community translations.

When building the following targets are available:

  • ninja ALL_MULTILANG: build all multi-language targets (default)
  • ninja ALL_ENGLISH: build all single-language targets
  • ninja ALL_FIRMWARE: build all single and multi-language targets
  • ninja VARIANT_ENGLISH: build the single-language version of VARIANT
  • ninja VARIANT_MULTILANG: build the multi-language version of VARIANT
  • ninja check_lang: build and check all language translations
  • ninja check_lang_ISO: build and check all variants with language ISO
  • ninja check_lang_VARIANT: build and check all languages for VARIANT
  • ninja check_lang_VARIANT_ISO: build and check language ISO for VARIANT

Automated tests

Automated tests are built with cmake by configuring for the current host:

# clone the repository
git clone
cd Prusa-Firmware

# automatically setup dependencies

# configure and build
mkdir build
cd build
cmake .. -G Ninja

# run the tests


PF-build is recommended for users without development experience. Download or clone the repository, then run PF-build and simply follow the instructions:

cd Prusa-Firmware

PF-build currently assumes a Debian/Ubuntu (or derivative) distribution.


Visual Studio Code (VSCode)


First time setup

Start by cloning the Prusa-Firmware repository

git clone

Open the Prusa-Firmware folder in VScode.

Open a new terminal in VScode (Terminal→New Terminal) and run

python .\utils\

This will download all dependencies required to build the firmware. You should see a .dependencies folder in the Prusa-Firmware folder.

Reload VScode. If all works correctly you should see the VScode automatically configuring the CMake project for you. If this doesn't happen you likely need to set the CMake kit; This can be done in two ways:

  1. Type Ctrl+Shift+P and search for CMake: Select a Kit. Select avr-gcc. If none appear, Scan for kits first.
  2. If 1) does not work for some reason, as a last resort you can edit the CMake Tools settings. Search for "Additional Kits" and add .vscode/cmake-kits.json to the list.

After updating the kit, you may need to reload VScode.


To start building a firmware, click the CMake Tools plugin icon on the far left side. You will get a very large list of targets to build. Find the firmware you'd like to build (like MK3S_ENGLISH) and select the small icon which shows "Build" when hovered over.

The built .hex file can then be found in folder Prusa-Firmware/build

Arduino IDE (deprecated)

Using Arduino IDE is still possible, but no longer supported. Prusa-Firmware requires a complex multi-step build process that cannot be done automatically with just the IDE. For a long time we provided instructions to use Arduino in combination with shell scripts, however starting with 3.13 the build system has been completely switched to cmake.

Building with Arduino IDE results in a limited firmware:

  • Arduino IDE can only build a single, english-only variant at a time that you manually have to select
  • The build will not be reproducible (meaning you will likely get a different binary every time you build the same sources)
  • You need to download, patch and select the correct board definitions by hand

For these reasons, you should think twice before reporting issues for a firmware built with Arduino. If you find a bug in the firmware, building and testing using CMake should be your first thought. Issues regarding Arduino builds are answered by the community and are not officially supported.

Environment preparation

Install "Arduino Software IDE" from the official website -> Software -> Downloads. Version 1.8.19 or higher is required.

Setup Arduino to install and use the Prusa board definitions:

  • Open Arduino and navigate to File -> Preferences -> Settings
  • To the text field "Additional Boards Manager URLs" add
  • Open Board manager (Tools -> Board -> Board manager)
  • Install "Prusa Research AVR Boards by Prusa Research"

Source code preparation

Clone or download this repository to your local drive.

In the subdirectory Firmware/variants/ select the configuration file (.h) corresponding to your printer model and manually copy it to Firmware/Configuration_prusa.h

Run "Arduino IDE", then

  • Open the file Firmware/Firmware.ino
  • Select the target board with Tools -> Board -> "PrusaResearch Einsy RAMBo"
  • Open Firmware/config.h and change LANG_MODE to 0.

Compilation and upload

  • Run the compilation: Sketch -> Verify/Compile
  • Upload the result code into the connected printer: Sketch -> Upload