RE: Bootloader difference and implementation from SDK 14 to SDK 16

Einar Thorsrud — Mon, 06 Jan 2020 13:31:24 GMT

Hi,

There is a new SoftDevice helper library, so you will find much of the same information in nrf_sdm.h. There you have SD_SIZE_GET(), for instance. There you also have SD_FLASH_SIZE macro, specifying the SoftDevice size excluding the MBR. The MBR_SIZE is specified in nrf_mbr.h, and is always 0x1000. This means that the Start of the SoftDevice is always at MBR_SIZE (since it is immediately after), and the start of the application is always at (SD_FLASH_SIZE + MBR_SIZE).

The BOOTLOADER_START_ADDR concept is used in the bootloader, but since you have your own bootloader it may not be relevant? The key point is just that you need to provide the start address of your bootloader to the MBR, which you do by writing the start address of your bootloader to the dedicated register in the UICR (0x10001014). You can search for "uicr_bootloader_start_address"in SDK 16 to see how it is done in our example bootloader.

SDK 16 does not include a "background" DFU bootloader example, but it is possible to implement this using the DFU modules we provide so that the application is responsible for validating and transferring the image, leaving only the activation to the bootloader. Though there are no examples, this has been discussed a few times, for instance in this thread.