This is the documentation for the latest (main) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down menu on the left and select the desired version.

Zephyr 3.5.0 (Working Draft)

We are pleased to announce the release of Zephyr version 3.5.0.

Major enhancements with this release include:

The following sections provide detailed lists of changes by component.



  • ARM

    • Architectural support for Arm Cortex-M has been separated from Arm Cortex-A and Cortex-R. This includes separate source modules to handle tasks like IRQ management, exception handling, thread handling and swap. For implementation details see GitHub #60031.

  • ARM

  • ARM64

  • RISC-V

  • Xtensa


  • Audio

  • Direction Finding

  • Host

  • Mesh

  • Controller

  • HCI Driver

Boards & SoC Support

  • Added support for these SoC series:

    • Nuvoton NuMaker M46x series

  • Removed support for these SoC series:

  • Made these changes in other SoC series:

    • i.MX RT SOCs no longer enable CONFIG_DEVICE_CONFIGURATION_DATA by default. boards using external SDRAM should set CONFIG_DEVICE_CONFIGURATION_DATA and CONFIG_NXP_IMX_EXTERNAL_SDRAM to enabled.

    • i.MX RT SOCs no longer support CONFIG_OCRAM_NOCACHE, as this functionality can be achieved using devicetree memory regions

  • Added support for these ARC boards:

  • Added support for these ARM boards:

    • Nuvoton NuMaker Platform M467

  • Added support for these ARM64 boards:

  • Added support for these RISC-V boards:

  • Added support for these X86 boards:

  • Added support for these Xtensa boards:

  • Made these changes for ARC boards:

  • Made these changes for ARM boards:

  • Made these changes for ARM64 boards:

  • Made these changes for RISC-V boards:

  • Made these changes for X86 boards:

  • Made these changes for Xtensa boards:

  • Removed support for these ARC boards:

  • Removed support for these ARM boards:

  • Removed support for these ARM64 boards:

  • Removed support for these RISC-V boards:

  • Removed support for these X86 boards:

  • Removed support for these Xtensa boards:

  • Made these changes in other boards:

  • Added support for these following shields:

Build system and infrastructure

  • SCA (Static Code Analysis)

    • Added support for CodeChecker

  • Twister now supports required_snippets in testsuite .yml files, this can be used to include a snippet when a test is ran (and exclude any boards from running that the snippet cannot be applied to).

  • Interrupts

    • Added support for shared interrupts

  • Added support for setting MCUboot encryption key in sysbuild which is then propagated to the bootloader and target images to automatically create encrypted updates.

Drivers and Sensors

  • ADC

  • Battery-backed RAM

  • CAN

  • Clock control

    • Added support for Nuvoton NuMaker M46x

  • Counter

  • Crypto

  • DAC

  • DFU

  • Disk

  • Display

    • Added support for ST7735S (in ST7735R driver)

  • DMA


  • Entropy

  • ESPI

  • Ethernet

  • Flash

    • Introduce npcx flash driver that supports two or more spi nor flashes via a single Flash Interface Unit (FIU) module and Direct Read Access (DRA) mode for better performance.

    • Added support for Nuvoton NuMaker M46x embedded flash

  • FPGA

  • Fuel Gauge

  • GPIO

    • Added support for Nuvoton NuMaker M46x

  • hwinfo

  • I2C

  • I2S

  • I3C

  • IEEE 802.15.4

    • A new mandatory method attr_get() was introduced into ieee802154_radio_api. Drivers need to implement at least IEEE802154_ATTR_PHY_SUPPORTED_CHANNEL_PAGES and IEEE802154_ATTR_PHY_SUPPORTED_CHANNEL_RANGES.

    • The hardware capabilities IEEE802154_HW_2_4_GHZ and IEEE802154_HW_SUB_GHZ were removed as they were not aligned with the standard and some already existing drivers couldn’t properly express their channel page and channel range (notably SUN FSK and HRP UWB drivers). The capabilities were replaced by the standard conforming new driver attribute IEEE802154_ATTR_PHY_SUPPORTED_CHANNEL_PAGES that fits all in-tree drivers.

    • The method get_subg_channel_count() was removed from ieee802154_radio_api. This method could not properly express the channel range of existing drivers (notably SUN FSK drivers that implement channel pages > 0 and may not have zero-based channel ranges or UWB drivers that could not be represented at all). The method was replaced by the new driver attribute IEEE802154_ATTR_PHY_SUPPORTED_CHANNEL_RANGES that fits all in-tree drivers.

  • Interrupt Controller

    • GIC: Architecture version selection is now based on the device tree

  • IPM


  • LED

  • MBOX

  • MEMC

  • PCIE

  • PECI

  • Pin control

    • Added support for Nuvoton NuMaker M46x

  • PWM

  • Power domain

  • Regulators

  • Reset

    • Added support for Nuvoton NuMaker M46x

  • Retained memory

  • SDHC

  • Sensor

  • Serial

    • Added support for Nuvoton NuMaker M46x

    • NS16550: Reworked how device initialization macros.

      • CONFIG_UART_NS16550_ACCESS_IOPORT and CONFIG_UART_NS16550_SIMULT_ACCESS are removed. For UART using IO port access, add “io-mapped” property to device tree node.

  • SPI

    • Remove npcx spi driver implemented by Flash Interface Unit (FIU) module.

  • Timer

    • The TI CC13xx/26xx system clock timer compatible was changed from ti,cc13xx-cc26xx-rtc to ti,cc13xx-cc26xx-rtc-timer and the corresponding Kconfig option from CC13X2_CC26X2_RTC_TIMER to CC13XX_CC26XX_RTC_TIMER for improved consistency and extensibility. No action is required unless the internal timer was modified.

  • USB

  • W1

  • Watchdog

  • WiFi


  • Time and timestamps in the network subsystem, PTP and IEEE 802.15.4 were more precisely specified and all in-tree call sites updated accordingly. Fields for timed TX and TX/RX timestamps have been consolidated. See net_time_t, net_ptp_time, ieee802154_config, ieee802154_radio_api and net_pkt for extensive documentation. As this is largely an internal API, existing applications will most probably continue to work unchanged.

  • CoAP:

    • Use 64 bit timer values for calculating transmission timeouts. This fixes potential problems for devices that stay on for more than 49 days when the 32 bit uptime counter might roll over and cause CoAP packets to not timeout at all on this event.

  • LwM2M:

  • Wi-Fi * Added Passive scan support. * The Wi-Fi scan API updated with Wi-Fi scan parameter to allow scan mode selection.


  • USB device HID * Kconfig option USB_HID_PROTOCOL_CODE, deprecated in v2.6, is finally removed.


Libraries / Subsystems

  • Management

    • Introduced MCUmgr client support with handlers for img_mgmt and os_mgmt.

    • Added response checking to MCUmgr’s MGMT_EVT_OP_CMD_RECV notification callback to allow applications to reject MCUmgr commands.

    • MCUmgr SMP version 2 error translation (to legacy MCUmgr error code) is now supported in function handlers by setting mg_translate_error of mgmt_group when registering a group. See smp_translate_error_fn for function details.

    • Fixed an issue with MCUmgr img_mgmt group whereby the size of the upload in the initial packet was not checked.

    • Fixed an issue with MCUmgr fs_mgmt group whereby some status codes were not checked properly, this meant that the error returned might not be the correct error, but would only occur in situations where an error was already present.

    • Fixed an issue whereby the SMP response function did not check to see if the initial zcbor map was created successfully.

    • Fixes an issue with MCUmgr shell_mgmt group whereby the length of a received command was not properly checked.

    • Added optional mutex locking support to MCUmgr img_mgmt group, which can be enabled with CONFIG_MCUMGR_GRP_IMG_MUTEX.

    • Added MCUmgr settings management group, which allows for manipulation of zephyr settings from a remote device, see Settings (Config) Management Group for details.

    • Added CONFIG_MCUMGR_GRP_IMG_ALLOW_CONFIRM_NON_ACTIVE_IMAGE_SECONDARY and CONFIG_MCUMGR_GRP_IMG_ALLOW_CONFIRM_NON_ACTIVE_IMAGE_ANY that allow to control whether MCUmgr client will be allowed to confirm non-active images.

    • Added CONFIG_MCUMGR_GRP_IMG_ALLOW_ERASE_PENDING that allows to erase slots pending for next boot, that are not revert slots.

    • Added user_data as an optional field to mgmt_handler when CONFIG_MCUMGR_MGMT_HANDLER_USER_DATA is enabled.

    • Added optional force parameter to os mgmt reset command, this can be checked in the MGMT_EVT_OP_OS_MGMT_RESET notification callback whose data structure is os_mgmt_reset_data.

    • Added configurable number of SMP encoding levels via CONFIG_MCUMGR_SMP_CBOR_MIN_ENCODING_LEVELS, which automatically increments minimum encoding levels for in-tree groups if CONFIG_ZCBOR_CANONICAL is enabled.

  • File systems

    • Added support for ext2 file system.

    • Added support of mounting littlefs on the block device from the shell/fs.

    • Added alignment parameter to FS_LITTLEFS_DECLARE_CUSTOM_CONFIG macro, it can speed up read/write operation for SDMMC devices in case when we align buffers on CONFIG_SDHC_BUFFER_ALIGNMENT, because we can avoid extra copy of data from card bffer to read/prog buffer.

  • Retention

  • Binary descriptors


  • Nuvoton

    • Added Nuvoton NuMaker M46x


  • Added CONFIG_MCUBOOT_BOOTLOADER_NO_DOWNGRADE that allows to inform application that the on-board MCUboot has been configured with downgrade prevention enabled. This option is automatically selected for DirectXIP mode and is available for both swap modes.

  • Added CONFIG_MCUBOOT_BOOTLOADER_MODE_OVERWRITE_ONLY that allows to inform application that the on-board MCUboot will overwrite the primary slot with secondary slot contents, without saving the original image in primary slot.

  • Fixed issue with serial recovery not showing image details for decrypted images.

  • Fixed issue with serial recovery in single slot mode wrongly iterating over 2 image slots.

  • Fixed an issue with boot_serial repeats not being processed when output was sent, this would lead to a divergence of commands whereby later commands being sent would have the previous command output sent instead.

  • Fixed an issue with the boot_serial zcbor setup encoder function wrongly including the buffer address in the size which caused serial recovery to fail on some platforms.

  • Fixed wrongly building in optimize for debug mode by default, this saves a significant amount of flash space.

  • Fixed issue with serial recovery use of MBEDTLS having undefined operations which led to usage faults when the secondary slot image was encrypted.

  • Added error output when flash device fails to open and asserts are disabled, which will now panic the bootloader.

  • Added currently running slot ID and maximum application size to shared data function definition.

  • Added P384 and SHA384 support to imgtool.

  • Added optional serial recovery image state and image set state commands.

  • Added dumpinfo command for signed image parsing in imgtool.

  • Added getpubhash command to dump the sha256 hash of the public key in imgtool.

  • Added support for getpub to print the output to a file in imgtool.

  • Added support for dumping the raw versions of the public keys in imgtool.

  • Added support for sharing boot information with application via retention subsystem.

  • Added support for serial recovery to read and handle encrypted seondary slot partitions.

  • Removed ECDSA P224 support.

  • Removed custom image list boot serial extension support.

  • Reworked boot serial extensions so that they can be used by modules or from user repositories by switching to iterable sections.

  • Reworked image encryption support for Zephyr, static dummy key files are no longer in the code, a pem file must be supplied to extract the private and public keys. The Kconfig menu has changed to only show a single option for enabling encryption and selecting the key file.

  • Reworked the ECDSA256 TLV curve agnostic and renamed it to ECDSA_SIG.

  • CDDL auto-generated function code has been replaced with zcbor function calls, this now allows the parameters to be supplied in any order.

  • The MCUboot version in this release is version 2.0.0+0-rc1.


Trusted Firmware-M

Trusted Firmware-A

  • Updated to TF-A 2.9.0.



Tests and Samples

  • Created common sample for file systems (fs_sample). It originates from sample for FAT (fat_fs) and supports both FAT and ext2 file systems.

Known Issues