Arduino IDE Burn Bootloader menu option will pick the correct bootloader binary for your selected board and prevent any command typos or other common errors.
First select the correct board you are using under Tools -> Board
Then select "Bootloader DFU for Bluefruit nRF52" for Tools->Programmer
Double check all of the following: Board, Programmer...
Then select Tools->Burn Bootloader to start the upgrade.
After receiving the new Bootloader over the serial connection, the old Bootloader will erase itself! The new bootloader will then be flashed. The process typically takes 30-60 seconds to complete. Make sure you see the "Device programmed" in the output log before launching Serial monitor or uploadinga new sketch.
Upgrading target on /dev/ttyACM0 with DFU package /Adafruit_nRF52_Arduino/bootloader/feather_nrf52840_express/feather_nrf52840_express_bootloader-0.6.2_s140_6.1.1.zip. Flow control is disabled, Dual bank, Touch 1200 Touched serial port /dev/ttyACM0 Opened serial port /dev/ttyACM0 Starting DFU upgrade of type 3, SoftDevice size: 151016, bootloader size: 39000, application size: 0 Sending DFU start packet Sending DFU init packet Sending firmware file ######################################## ######################################## ######################################## ######################################## ######################################## ######################################## ######################################## ######################################## ######################################## ############ Activating new firmware DFU upgrade took 20.50154972076416s Device programmed.
The drawbacks is the bundled bootloader may not be the latest one and you will need to install Arduino IDE. Check out the next page for more advanced command line version
