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This repository contains the official implementation ofArduino Core for Zephyr RTOS based board.

Zephyr RTOS is an open-source, real-time operating system designed for low-power, resource-constrained devices. It's modular, scalable, and supports multiple architectures.

Install the core and its toolchains via Board Manager:

• Download and install the latestArduino IDE (only versions2.x.x are supported).
• Open the'Settings / Preferences' window.
• Open the'Boards Manager' from the side menu and search for'Zephyr'.
  • If it doesn’t appear, add the following URL to the'Additional Boards Manager URLs' field:https://downloads.arduino.cc/packages/package_zephyr_index.json (if you have multiple URLs, separate them with a comma).
• Install theArduino Zephyr Boards platform.

Alternatively, to install the core using the command line, run the following command with the Arduino CLI:

arduino-cli core install arduino:zephyr --additional-urls https://downloads.arduino.cc/packages/package_zephyr_index.json

To get started with your board:

• Put the board in bootloader mode by double-clicking the RESET button.
• Run theBurn Bootloader option from the IDE/CLI.
  • Note that due to limitations in the Arduino IDE, you may need to select any programmer from theProgrammers menu.
• Once the bootloader is installed, you can load your first sketch by placing the board into bootloader mode again.

A: Connect a USB-to-UART adapter to the default UART (eg. TX0/RX0 on Giga, TX/RX on Nano) and read the error message (with the sketch compiled inDefault mode). If you don't own a USB-to-UART adapter, compile the sketch inDebug mode; this will force the shell to wait until you open the Serial Monitor. Then, runsketch command andprobably you'll be able to read the error (if generated byllext). For OS crashes, the USB-to-UART adapter is the only way to collect the crash.

A: This means you are trying to use a Zephyr function which has not yet been exported. Openllext_exports.c, add the function you need and recompile/upload the loader.

A: Open the.conf file for your board, add the requiredCONFIG_, recompile/upload the loader.

A: This is usually due to a buffer overflow or coding error in the user's own code. However, since the project is still in beta 🧪, agood bug report could help identify any issues in our code.

A: Since collecting bug reports is very important at this time, we are keeping Zephyr's shell enabled to allow loading a full sketch (which requires a large stack). Adjust your board's.conf file to reduce the stack size if your platform doesn't have enough RAM.

• ArduinoBLE: This library is enabled only for the Arduino Nano 33 BLE. Please usethis branch to test it.

Unlike traditional Arduino implementations, where the final output is a standalone binary loaded by a bootloader, this core generates a freestandingelf file. This file is dynamically loaded by a precompiled Zephyr firmware, referred to as theloader.

Theloader is responsible for managing the interaction between your sketches and the underlying Zephyr system. After the initial bootloader installation, theloader takes over the sketch loading process automatically.

To ensure flexibility, theloader project is designed to be generic. Any necessary modifications for specific boards should be made in the correspondingDTS overlay or a specialfixup file, using appropriate guards to maintain stability.

The behavior of theloader can be adjusted through theMode menu:

• Standard: The sketch is loaded automatically.
• Debug: The user must typesketch in Zephyr's shell, which is accessible via the default Serial.

The most important components of this project are:

• Zephyr based loader
• LLEXT
• Actual core withvariants and the usual{platform,boards}.txt
• ArduinoCore-API
• post_build_tool

In this section, we’ll guide you through setting up your environment to work with the core.

Shell scripts are available to simplify the installation process (Windows is not supported at the moment 😔).

mkdir my_new_zephyr_folder&&cd my_new_zephyr_foldergit clone https://github.com/arduino/ArduinoCore-zephyr

Before running the installation script, ensure that Python,pip andvenv are installed on your system. The script will automatically installwest and manage the necessary dependencies.

On Ubuntu or similarapt-based distros, make sure to run the following command:

sudo apt install python3-pip python3-setuptools python3-venv build-essential git cmake ninja-build zstd jq

cd ArduinoCore-zephyr./extra/bootstrap.sh

Download and install the Zephyr SDK for your OS fromhere.

To build the loader, run the following commands:

export ZEPHYR_SDK_INSTALL_DIR=$folder_where_you_installed_the_sdk./extra/build.sh$zephyr_board_name$arduino_variant_board_name

Replace$zephyr_board_name and$arduino_variant_board_name with the appropriate names for your board.

Example for Arduino Portenta H7:

./extra/build.sh arduino_portenta_h7//m7 arduino_portenta_h7

The firmwares will be copied tofirmwares folder.

If the board is fully supported by Zephyr, you can flash the firmware directly onto the board using the following command:

west flash

After running thebootstrap script, you can symlink the core to$sketchbook/hardware/arduino-git/zephyr. Once linked, it will appear in the IDE/CLI, and the board's Fully Qualified Board Name (FQBN) will be formatted asarduino-git:zephyr:name_from_boards_txt.

To add a new board that is already supported by mainline Zephyr, follow these steps:

• Create theDTS overlay and.conf files in theloader directory.The overlay must include:
  • A flash partition calleduser_sketch, tipically located near the end of the flash.
  • Azephyr,user section containing the description for GPIOs, Analog, UART, SPI and I2C devices. Feel free to leave some fields empty in case Zephyr support is missing. This will result in some APIs not being available at runtime (eg.analogWrite if PWM section is empty).
• Build the Loader: run./extra.build.sh $your_board $your_board and start debugging the errors. 😁
• Update theboards.txt: add an entry for your board, manually filling the required fields.
• Implement touch support: if your board supports the1200bps touch method, implement_on_1200_bps in a file located inside thevariant/your_board folder.
• ⏳ Temporary steps
  • Createincludes.txt based onllext-edk/Makefile.cflags, taking inspiration for other variants.
  • Amendyour_board.compiler.zephyr.* with information fromllext-edk/Makefile.cflags.

To report a bug, open theissues and follow the instructions. Any issue opened without the needed information will be discarded.

Contributions are always welcome. The preferred way to receive code contribution is by submitting aPull request.

• Unify overlay inloader with the one provided invariant for interoperability with GSoC project
• Autogeneratedefines.txt,includes.txt,cflags.txt fromllext-edk output
• Network: support UDP and TLS
• USB: switch to USB_DEVICE_STACK_NEXT to support PluggableUSB
• Relocate RODATA in flash to accomodate sketches with large assets
• Provide better error reporting for failed llext operations
• Replacellext_exports.c with proper symbols generation (via includes)
• Provide better usability forDebug builds (eg. shell over USB)
• Fix corner cases withstd:: includes (like<iterator>)
• Get rid of all warnings

This effort would have been very hard without theGSoC project and the Zephyr community.