embassy-boot-nrf

An Embassy project.

An adaptation of embassy-boot for nRF.

Features

• Load applications with or without the softdevice.
• Configure bootloader partitions based on linker script.
• Using watchdog timer to detect application failure.

Working with a SoftDevice

When a SoftDevice is present, it handles starting the bootloader and the application as needed.

The SoftDevice architecture supports the bootloader via a configurable base address, referred to as BOOTLOADERADDR, in the application flash region. This address can be specified either:

1. At the MBR_BOOTLOADER_ADDR location in flash memory (defined in nrf_mbr.h), or
2. In the UICR.NRFFW[0] register.

The UICR.NRFFW[0] register is used only if MBR_BOOTLOADER_ADDR has its default value of 0xFFFFFFFF. This bootloader relies on the latter approach.

In the memory.x linker script, there is a section .uicr_bootloader_start_address (origin 0x10001014, length 0x4) that stores the BOOTLOADERADDR value. Ensure that __bootloader_start is set to the origin address of the bootloader partition.

When a bootloader is present, the SoftDevice forwards interrupts to it and executes the bootloader reset handler, defined in the bootloader's vector table at BOOTLOADERADDR.

Once the bootloader loads the application, the SoftDevice initiates the Application Reset Handler, defined in the application’s vector table at APP_CODE_BASE hardcoded in the SoftDevice. The active partition's origin must match the APP_CODE_BASE value hardcoded within the SoftDevice. This value can be found in the release notes for each SoftDevice version.