The IDE allows for multiple versions of the same core to be installed simultaneously. This can be useful for testing purposes, or for solving compatibility issues with a specific core version.

In this guide, we’ll create the appropriate folder structure and install a core.

1. Creating the folder structure

You can skip this step if you already have a folder.

In the commands below, <sketchbook> refers to the location of your sketchbook folder. It is typically located in the Arduino subfolder of your Documents folder, but you can find the location in the IDE preferences under Sketchbook location.

The preferred folder structure is

<sketchbook>/hardware/<vendor>/<architecture>/

We recommend you follow this naming convention as this will ensure proper determination of library compatibility and permit referencing resources from other cores of the same architecture.

For Arduino cores, the <architecture> name may correspond to the x in ArduinoCore-x. Consulting relevant documentation is recommended, however.

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Follow these steps to create the appropriate folder structure.

1. Open the sketchbook folder.
2. In the sketchbook folder, create a folder called hardware. Open it.
3. Inside the hardware folder, create the <vendor> folder. This can have any arbitrary unique vendor name, e.g. arduino or arduino-git.

2. Installing the core

The core can be downloaded with a web browser or by cloning the git repo.

Using your web browser

1. Download the git repo. In GitHub this is done by clicking Code > Download ZIP.
2. Extract the core into <sketchbook>/Arduino/hardware/<vendor>/<architecture>.

Using git

Simply navigate into Arduino/hardware/<vendor> and clone the repo into a folder named <architecture>.

cd <sketchbook>/hardware/<vendor>
git clone <repo URL> <architecture>

If we wanted to clone arduino/ArduinoCore-avr into the vendor folder arduino, we’d use the following command.

cd <sketchbook>/hardware/arduino
git clone https://github.com/arduino/ArduinoCore-avr avr

Often the bugfix may not be on the main branch. After cloning the repo, we can switch branches with the following command.

git checkout <bugfix-branch>

3. Installing the ArduinoCore-API

The Mbed OS, SAMD, and megaAVR boards platforms (as well as AVR in the near future and any new platforms that are created) use ArduinoCore-API, which contains all the non-architecture specific code that can be shared between all core libraries. This must be installed in addition to the board platform.

Installing the ArduinoCore-API

You can skip this step if you already have the ArduinoCore-API installed, or if it’s not needed by your platform.

Download and extract the API, or clone it, into a directory of your choice.

git clone git@github.com:arduino/ArduinoCore-API

Symlink the ArduinoCore-API

On macOS/Linux (using Terminal):

ln -s "<ArduinoCore-API_path>/api" "<core_path>/cores/arduino/api"

On Windows (using cmd.exe):

mklink /D "<core_path>\cores\arduino\api" "<ArduinoCore-API_path>\api"

4. Using the core

Restart the IDE if open. The new core will now be available in Tools > Board > [core_name] (in sketchbook).