Zephyr 4.0.0 is released!

[dkalowsk]

Hi Zephyr developers!

We are pleased to announce the release of Zephyr 4.0.0:

https://github.com/zephyrproject-rtos/zephyr/releases/tag/v4.0.0

For a detailed overview of this release and a summary of the various new features and highlights please see the dedicated post on the Zephyr project blog (https://www.zephyrproject.org/zephyr-4-0-is-generally-available) or if you prefer the companion video (https://www.youtube.com/watch?v=uEdZCWPftxQ).

This release is the first 4.x release and will be supported until July 18th, 2025.

Major enhancements with this release include:

• Secure Storage Subsystem
  A newly introduced secure storage subsystem allows the use of the PSA Secure Storage API and of persistent keys in the PSA Crypto API on all board targets. It is now the standard way to provide device-specific protection to data at rest.

• ZMS (Zephyr Memory Storage) Subsystem
  ZMS is a new key-value storage subsystem compatible with all non-volatile storage types, including traditional NOR flash and advanced technologies like RRAM and MRAM that support write without erasure.

• Analog Comparators
  A new comparator device driver subsystem for analog comparators has been added, complete with shell support. It supports initial configuration through Devicetree and runtime configuration through vendor specific APIs. Initially the nordic,nrf-comp, nordic,nrf-lpcomp and nxp,kinetis-acmp are supported.

• Stepper Motors
  It is now possible to interact with stepper motors using a standard API thanks to the new stepper device driver subsystem, which also comes with shell support. Initially implemented drivers include a simple zephyr,gpio-steppers and a complex sensor-less stall-detection capable with integrated ramp-controller adi,tmc5041.

• Haptics
  A new haptics device driver subsystem allows unified access to haptic controllers, enabling users to add haptic feedback to their applications.

• Multimedia Capabilities
  Zephyr's audio and video capabilities have been expanded with support for new image sensors, video interfaces, audio interfaces, and codecs being supported.

• Prometheus Library
  A Prometheus metrics library has been added to the networking stack. It provides a way to expose metrics to Prometheus clients over HTTP, facilitating the consolidated remote monitoring of Zephyr devices alongside other systems typically monitored using Prometheus.

• Documentation Improvements
  Several enhancements were made to the online documentation to improve content discovery and navigation. These include a new interactive board catalog and an interactive directory for code samples.

• Expanded Board Support
  Over 60 new boards and shields are supported in Zephyr 4.0.

An overview of the changes required or recommended when migrating your application from Zephyr v3.7.0 to Zephyr v4.0.0 can be found in the separate migration guide.

The full release notes and major changes since the last release can be found here:

https://docs.zephyrproject.org/latest/releases/release-notes-4.0.html

A big thanks to everyone who contributed to this release,

Mahesh, Dan, and the Zephyr Release Team