https://devzone.nordicsemi.com/f/nordic-q-a/76207/internal-dfuHi, I am working on a bootloader that can do DFU for my nrf52840 DK. Currently, when the bootloader goes into DFU mode, it obtains the init packet via UART. Then, after executing the init packet the bootloader will start writing the firmware image toen-USTelligent Community 13Fri, 11 Jun 2021 11:30:07 GMThttps://devzone.nordicsemi.com/thread/314893?ContentTypeID=1Fri, 11 Jun 2021 11:30:07 GMT137ad170-7792-4731-bb38-c0d22fbe4515:eac9bda2-0bde-4582-89ed-91f40b434599Vidar Berg<p>Hi,</p> <p>I don&#39;t see any reasons for why this shouldn&#39;t work, but you will have to modify the bootloader to check (this check may be conditional based on GREPREGET value, etc) for available updates in external flash on startup, and implement a routine that reads and validates the init command from ext. flash before activating the new update.</p><div style="clear:both;"></div>