Datasheet

Using the Bootloader

The Bluefruit nRF52 Feather includes a customized version of the Nordic bootloader that enables serial support, over

the air (OTA) DFU support, and various fail safe features like factory reset when the FRST pin is grounded at startup.

The bootloader that all Bluefruit nRF52 Feathers ships with allows you to flash user sketches to the nRF52832 using

only the CP2104 USB to serial adapter populated on the board.

Forcing Serial Boot Mode

The Bluefruit nRF52 Feather is designed to briefly enter serial bootloader mode for a short delay every time the device

comes out of reset, and the DTR line on the CP2104 USB to Serial adapter will trigger a reset every time the Serial

Monitor is opened. This means that you can normally flash a user sketch to the nRF52 with no manual intervention on

your part at a HW level.

If you need to force the serial bootloader mode, however, you can connect the DFU pin to GND at startup, which will

force you to enter serial bootloader mode and stay in that mode until you reset or power cycle the board.

This can be used to recover bricked boards where a bad user sketch has been uploaded, since you will enter serial

bootloader mode without executing the user sketch, and you can flash a new sketch directly from the Arduino IDE.

This page is for information purposes only. Normally the bootloader will work transparently and automatically

from the Arduino IDE, requiring no manual intervention on your behalf.

Forcing the serial bootloader can often be used to recover bricked devices.

nRF52840-based board can also use double reset trick to force into serial bootloader