User's Manual

5 Programming
The nRF52840 Dongle can be programmed through the built-in USB bootloader.
Before you start, check Getting started on page 8.
To program the Dongle, it must be in bootloader mode.
The Dongle can be made to enter bootloader mode in one of the two ways:
• Trigger the nRF52840 USB DFU endpoint.
The firmware to support this is embedded in all nRF Connect for Desktop apps for the
nRF52840Dongle. If you add the DFU Trigger Library (USB) to your custom device firmware, you
will be able totrigger the DFU from nRF Connect for Desktop without using any buttons. For
documentation, see DFUTrigger Library (USB), which is part of the nRF5 SDK v15.2.0.
• For Dongles with applications missing the USB DFU endpoint: Press the RESET button.
When the nRF52840 Dongle has entered the bootloader mode, LD2 pulses red. The Dongle is
now readyfor programming.
All the nRF Connect for Desktop apps require specific firmware to be present on the nRF52840
Dongle tofunction correctly. The apps will update the firmware if needed. If you want to upload a
custom firmwareto the Dongle, you can do this by using the dedicated Programmer
programming app, or nrfutil