nRF Util: Generating and displaying bootloader settings

Use the settings command to generate and display a bootloader settings page.

A Device Firmware Update (DFU) bootloader requires a bootloader settings page that contains information about the current DFU process. In addition, it can contain information about the installed application and the firmware version.

Run nrfutil settings generate to generate a bootloader settings page and store it in a HEX file.
You can see available options by entering the following command:
```
nrfutil settings generate --help
```
Run nrfutil settings display to display the contents of a bootloader settings page that is present in a HEX file.
To read the bootloader settings page from a programmed device, use nrfjprog to dump the flash memory of the IC (where HEX_file is the name of the resulting HEX file):
```
nrfjprog --readcode HEX_file
```

After generating the bootloader settings page, you can use mergehex and nrfjprog to program it to the device. See the nRF Command Line Tools documentation for more information.

For example, enter the following command to generate a bootloader settings page for an nRF52840 device with the application app.hex installed, with application version 3, bootloader version 2, and bootloader settings version 1 (for SDK v13.0.0), and store it in a file named settings.hex:

nrfutil settings generate --family NRF52840 --application app.hex --application-version 3 --bootloader-version 2 --bl-settings-version 1 settings.hex

Enter the following command to display the contents of the generated HEX file:

nrfutil settings display settings.hex

Each nRF device has a corresponding --family setting:

Table 1. `--family` settings
Family setting	nRF devices
NRF51	nRF51xxx
NRF52	nRF52832, nRF52833
NRF52QFAB	nRF52832-QFAB, nRF52820
NRF52810	nRF52810, nRF52811, nRF52805
NRF52840	nRF52840

The --bl-settings-version depends on the SDK version:

Table 2. SDK and BL settings versions
SDK version	BL settings version
<=12.0	1
>=15.3.0	2

The DFU bootloader settings version supported and used by your selected SDK is listed in the nrf_dfu_types.h file in the bootloader library. Even though bootloaders compiled from an nRF5 SDK 15.3.0 or later can only use version 2, they can be configured to support a version 1 settings page. When a new bootloader with a version 1 settings page boots, the bootloader translates the settings page to version 2 before booting. If a version 2 settings page is used, boot validation for SoftDevice and Application can be generated with the settings page using the --sd-boot-validation and --app-boot-validation commands.