nRF52840 Preview DK v0.11.x

Swapping interface MCU firmware

The onboard interface MCU is factory-programmed with an mbed-compliant bootloader. This feature makes it possible to swap the interface firmware between the factory-preloaded SEGGER J-Link OB and the mbed interface firmware.

  1. Download the mbed interface firmware and the J-Link OB image from
  2. Enter the bootloader.
    See section IF Boot/Reset button on how to enter the bootloader.
  3. To swap the interface MCU firmware, drag the interface image (.bin) into the mounted bootloader drive on the connected computer.
  4. Power cycle the board.
  • The J-Link serial number is linked to the interface MCU and will not change even when swapping the interface MCU firmware.
  • When in bootloader mode, do not drag and drop any files except those downloaded from for use with the interface MCU. If a wrong file is used, it can overwrite the bootloader and ruin the interface MCU firmware without the possibility of recovery.