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Zephyr 2.5.0 (Working Draft)

We are pleased to announce the release of Zephyr RTOS version 2.5.0.

Major enhancements with this release include:

  • Introduced support for the SPARC processor architecture and the LEON processor implementation.

The following sections provide detailed lists of changes by component.

Known issues

You can check all currently known issues by listing them using the GitHub interface and listing all issues with the bug label.

API Changes

  • Removed SETTINGS_USE_BASE64 support as its been deprecated for more than two releases.

  • The lwm2m_rd_client_start() function now accepts an additional flags parameter, which allows to configure current LwM2M client session, for instance enable bootstrap procedure in the curent session.

  • LwM2M execute now supports arguments. The execute callback lwm2m_engine_execute_cb_t is extended with an args parameter which points to the CoAP payload that comprises the arguments, and an args_len parameter to indicate the length of the args data.

  • Changed vcnl4040 dts binding default for property ‘proximity-trigger’. Changed the default to match the HW POR state for this property.

  • The clock_control_async_on() function will now take callback and user_data as arguments instead of structure which contained list node, callback and user data.

  • The mqtt_keepalive_time_left() function now returns -1 if keep alive messages are disabled by setting CONFIG_MQTT_KEEPALIVE to 0.

  • The CONFIG_LEGACY_TIMEOUT_API mode has been removed. All kernel timeout usage must use the new-style k_timeout_t type and not the legacy/deprecated millisecond counts.

  • The coap_pending_init() function now accepts an additional retries parameter, allowing to specify the maximum retransmission count of the confirmable message.

  • The CONFIG_BT_CTLR_CODED_PHY is now disabled by default for builds combining both Bluetooth host and controller.

Deprecated in this release

  • Nordic nRF5340 PDK board deprecated and planned to be removed in 2.6.0.

  • ARM Musca-A board and SoC support deprecated and planned to be removed in 2.6.0.

  • DEVICE_INIT was deprecated in favor of utilizing DEVICE_DEFINE directly.


Removed APIs in this release

Stable API changes in this release



  • ARC

  • ARM

    • AARCH32

      • Introduced the functionality for chain-loadable Zephyr fimrmware images to force the initialization of internal architecture state during early system boot (Cortex-M).

    • AARCH64


  • RISC-V


    • Added support for the SPARC architecture, compatible with the SPARC V8 specification and the SPARC ABI.

    • FPU is supported in both shared and unshared FP register mode.

  • x86

Boards & SoC Support

  • Added support for these SoC series:

  • Made these changes in other SoC series:

  • Changes for ARC boards:

  • Added support for these ARM boards:

  • Added support for these SPARC boards:

    • GR716-MINI LEON3FT microcontroller development board

    • Generic LEON3 board configuration for GRLIB FPGA reference designs

    • SPARC QEMU for emulating LEON3 processors and running kernel tests

  • Made these changes in other boards:

    • nRF5340 DK: Selected TF-M as the default Secure Processing Element (SPE) when building Zephyr for the non-secure domain.

  • Added support for these following shields:

Drivers and Sensors

  • ADC

  • Audio

  • Bluetooth

  • CAN

  • Clock Control

  • Console

  • Counter

  • Crypto

  • DAC

  • Debug

  • Display

  • DMA


  • Entropy

  • ESPI

  • Ethernet

  • Flash

    • CONFIG_NORDIC_QSPI_NOR_QE_BIT has been removed. The quad-enable-requirements devicetree property should be used instead.

  • GPIO

  • Hardware Info

  • I2C

  • I2S

  • IEEE 802.15.4

  • Interrupt Controller

  • IPM

  • Keyboard Scan

  • LED

  • LED Strip

  • LoRa

  • Modem

  • PECI

  • Pinmux

  • PS/2

  • PWM

  • Sensor

  • Serial

  • SPI

  • Timer

  • USB

    • Made USB DFU class compatible with the target configuration that does not have a secondary image slot.

    • Support to use USB DFU within MCUBoot with single application slot mode.

  • Video

  • Watchdog

  • WiFi



  • Host

    • When privacy has been enabled in order to advertise towards a privacy-enabled peer the BT_LE_ADV_OPT_DIR_ADDR_RPA option must now be set, same as when privacy has been disabled.

  • Mesh

    • The bt_mesh_cfg_srv structure has been deprecated in favor of a standalone Heartbeat API and Kconfig entries for default state values.

  • BLE split software Controller

  • HCI Driver

Build and Infrastructure

  • Improved support for additional toolchains:

  • Devicetree

    • DT_ENUM_IDX_OR: new macro

    • Support for legacy devicetree macros via CONFIG_LEGACY_DEVICETREE_MACROS was removed. All devicetree-based code should be using the new devicetree API introduced in Zephyr 2.3 and documented in Devicetree access from C/C++. Information on flash partitions has moved to Flash map.

Libraries / Subsystems

  • Disk

  • Management

    • MCUmgr

      • Added support for flash devices that have non-0xff erase value.

      • Added optional verification, enabled via CONFIG_IMG_MGMT_REJECT_DIRECT_XIP_MISMATCHED_SLOT, of an uploaded Direct-XIP binary, which will reject any binary that is not able to boot from base address of offered upload slot.

    • updatehub

  • Settings

  • Random

  • POSIX subsystem

  • Power management

  • Logging

  • LVGL

    • Library has been updated to minor release v7.6.1

  • Shell

  • Storage

    • flash_map: Added API to get the value of an erased byte in the flash_area, see flash_area_erased_val().

  • Tracing

  • Debug

  • DFU

  • boot: Reworked using MCUBoot’s bootutil_public library which allow to use API implementation already provided by MCUboot codebase and remove zephyr’s own implementations.


  • HALs are now moved out of the main tree as external modules and reside in their own standalone repositories.


  • bootloader

    • Added hardening against hardware level fault injection and timing attacks, see CONFIG_BOOT_FIH_PROFILE_HIGH and similar kconfig options.

    • Introduced Abstract crypto primitives to simplify porting.

    • Added ram-load upgrade mode (not enabled for zephy-rtos yet).

    • Renamed single-image mode to single-slot mode, see CONFIG_SINGLE_APPLICATION_SLOT.

    • Added patch for turning off cache for Cortex M7 before chain-loading.

    • Fixed boostrapping in swap-move mode.

    • Fixed issue causing that interrupted swap-move operation might brick device if the primary image was padded.

    • Fixed issue causing that HW stack protection catches the chain-loaded application during its early initialization.

    • Added reset of Cortex SPLIM registers before boot.

    • Fixesd build issue that occurs if CONF_FILE contains multiple file paths instead of single file path.

    • Added watchdog feed on nRF devices. See CONFIG_BOOT_WATCHDOG_FEED option.

    • Removed the flash_area_read_is_empty() port implementation function.

    • Initialize the ARM core configuration only when selected by the user, see CONFIG_MCUBOOT_CLEANUP_ARM_CORE.

    • Allow the final data chunk in the image to be unaligned in the serial-recovery protocol.

    • Kconfig: allow xip-revert only for xip-mode.

    • ext: tinycrypt: update ctr mode to stream.

    • Use minimal CBPRINTF implementation.

    • Configure logging to LOG_MINIMAL by default.

    • boot: cleanup NXP MPU configuration before boot.

    • Fix nokogiri<=1.11.0.rc4 vulnerability.

    • bootutil_public library was extracted as code which is common API for MCUboot and the DFU application, see CONFIG_MCUBOOT_BOOTUTIL_LIB

  • imgtool

    • Print image digest during verify.

    • Add possibility to set confirm flag for hex files as well.

    • Usage of –confirm implies –pad.

    • Fixed ‘custom_tlvs’ argument handling.

    • Add support for setting fixed ROM address into image header.


  • Synchronized Trusted-Firmware-M module to the upstream v1.2.0 release.


Tests and Samples