.. _lib_dfu_multi_image:

DFU multi-image
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.. contents::
   :local:
   :depth: 2

The DFU multi-image library provides an API for writing a DFU multi-image package that can be downloaded in chunks of arbitrary size.
The DFU multi-image package is a simple archive file that consists of a CBOR-based header that describes contents of the package, followed by a number of updates images, such as firmware images for different MCU cores.

Images included in a DFU multi-image package are identified by numeric identifiers assigned by the user.
The library provides a way for the user to register custom functions for writing a single image with a given identifier.

Because the library makes no assumptions about the formats of images included in a written package, it serves as a general-purpose solution for device firmware upgrades.
For example, it can be used to upgrade the :ref:`nRF5340 <ug_nrf5340_multi_image>` firmware.

Configuration
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To enable the DFU multi-image library, set the :kconfig:option:`CONFIG_DFU_MULTI_IMAGE` Kconfig option.

To configure the maximum number of images that the DFU multi-image library is able to process, use the :kconfig:option:`CONFIG_DFU_MULTI_IMAGE_MAX_IMAGE_COUNT` Kconfig option.

To enable building the DFU multi-image package that contains commonly used update images, such as the application core firmware, the network core firmware, or MCUboot images, set the :kconfig:option:`CONFIG_DFU_MULTI_IMAGE_PACKAGE_BUILD` Kconfig option.

Dependencies
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This module uses the following |NCS| libraries and drivers:

* `zcbor`_

API documentation
*****************

| Header file: :file:`include/dfu/dfu_multi_image.h`
| Source files: :file:`subsys/dfu/dfu_multi_image/src/`

.. doxygengroup:: dfu_multi_image
   :project: nrf
   :members: