Application Flashing

The nRF52 Secure Bootloader requires that apps be digitally signed and flashed over the USB/BLE interface, meaning that you can't flash your application hex file via nrfjprog and expect things to work.

The flashing procedure is as follows:

1. Generate a .hex for your application.

If you're using Arduino, generate a hex by using the 'Export Compiled Binary' on your sketch.

2. Generate a signed package:

 nrfutil pkg generate --hw-version 52 --application-version 1 --application /path/to/compiled/program.hex --sd-req 0xB6 --key-file /path/to/kaidyth_nrf52_bootloader/default_private.pem app_dfu_package.zip

Note that you'll need to download the default private key bundled with the bootloader to sign your application. If you're using a custom key with your bootloader use that key instead.

3. Flash over USB

nrfutil dfu usb-serial --package app_dfu_package.zip -p /dev/ttyACM0

You can also use the nRF Connect mobile/desktop app to flash the program over Bluetooth DFU.