.. zephyr:code-sample:: usb-dfu
   :name: USB DFU (Device Firmware Upgrade)
   :relevant-api: usbd_api _usb_device_core_api

   Implement device firmware upgrade using the USB DFU class driver.

Overview
********

This sample app demonstrates use of a USB DFU Class driver provided
by the Zephyr project.

Requirements
************

This project requires an USB device driver. Currently, the USB DFU
class provided by the Zephyr project depends on DFU image manager and
partition layout. Refer to :ref:`flash_map_api` for details about
partition layout. You SoC must run MCUboot as the stage 1 bootloader.
This sample is built as an application for the MCUboot bootloader.

.. note::
   This example explicitly turns :kconfig:option:`CONFIG_USB_DFU_ENABLE_UPLOAD` on.

Building and Testing
********************

Building and signing the application
====================================

This sample can be built in the usual way (see :ref:`build_an_application`
for more details) and flashed with regular flash tools, but will need
to be loaded at the offset of SLOT-0.

Application images (such as this sample) must be signed.
The build system can do this for you by setting the :kconfig:option:`CONFIG_MCUBOOT_SIGNATURE_KEY_FILE` symbol.

For example:

.. code-block:: console

   west build -b nrf52840dk_nrf52840 zephyr/samples/subsys/usb/dfu -d build-dfu -- \
   -DCONFIG_MCUBOOT_SIGNATURE_KEY_FILE=\"bootloader/mcuboot/root-rsa-2048.pem\"

Build and flash MCUboot bootloader for Zephyr project as it is described in
the `Using MCUboot with Zephyr`_ documentation. Then build, sign and flash
the USB DFU sample at the offset of SLOT-0.

Build and sign a second application image e.g. :ref:`hello_world`,
which will be used as an image for the update.
Do not forget to enable the required :kconfig:option:`CONFIG_BOOTLOADER_MCUBOOT` option (as described
in :ref:`mcuboot`). For example:

.. code-block:: console

   west build -b nrf52840dk_nrf52840 zephyr/samples/hello_world -d build-hello_world -- \
   -DCONFIG_BOOTLOADER_MCUBOOT=y '-DCONFIG_MCUBOOT_SIGNATURE_KEY_FILE="bootloader/mcuboot/root-rsa-2048.pem"'

Testing
=======

The Linux ``dfu-util`` tool can be used to backup or update the application
image.

Use the following command to backup the SLOT-0 image:

.. code-block:: console

   dfu-util --alt 0 --upload slot0_backup.bin

Use the following command to update the application:

.. code-block:: console

   dfu-util --alt 1 --download build-hello_world/zephyr/zephyr.signed.bin

Reset the SoC. MCUboot boot will swap the images and boot the new application,
showing this output to the console:

.. code-block:: console

   *** Booting Zephyr OS build zephyr-v3.0.0-360-gc0dd594d4d3d  ***
   I: Starting bootloader
   I: Primary image: magic=good, swap_type=0x3, copy_done=0x1, image_ok=0x1
   I: Secondary image: magic=good, swap_type=0x2, copy_done=0x3, image_ok=0x3
   I: Boot source: none
   I: Swap type: test
   I: Bootloader chainload address offset: 0xc000
   I: Jumping to the first image slot
   *** Booting Zephyr OS build zephyr-v3.0.0-361-gb987e6daa2f9  ***
   Hello World! nrf52840dk_nrf52840


Reset the SoC again and MCUboot should revert the images and boot
USB DFU sample, showing this output to the console:

.. code-block:: console

   *** Booting Zephyr OS build zephyr-v3.0.0-360-gc0dd594d4d3d  ***
   I: Starting bootloader
   I: Primary image: magic=good, swap_type=0x2, copy_done=0x1, image_ok=0x3
   I: Secondary image: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
   I: Boot source: none
   I: Swap type: revert
   I: Secondary image: magic=unset, swap_type=0x1, copy_done=0x3, image_ok=0x3
   I: Bootloader chainload address offset: 0xc000
   I: Jumping to the first image slot
   *** Booting Zephyr OS build zephyr-v3.0.0-361-gb987e6daa2f9  ***
   [00:00:00.005,920] <inf> main: This device supports USB DFU class.

Permanent download and automatic reboot
=======================================

There are some symbols that can be used to enable a hands free download:

To mark SLOT-1 as permanent after the download completes,
enable the :kconfig:option:`CONFIG_USB_DFU_PERMANENT_DOWNLOAD` symbol.

To automatically reboot after the download completes,
enable the :kconfig:option:`CONFIG_USB_DFU_REBOOT` symbol.

.. warning::
   Enabling :kconfig:option:`CONFIG_USB_DFU_PERMANENT_DOWNLOAD` can lead to a bricked device!
   Make sure there is another way to download firmware.
   For example via a debugger or Mcuboot's recovery mode.

Both symbols can be enabled with the :file:`overlay-permanent-download.conf` overlay. For example:

.. code-block:: console

   west build -b nrf52840dk_nrf52840 zephyr/samples/subsys/usb/dfu -d build-dfu -- \
   -DCONFIG_BOOTLOADER_MCUBOOT=y '-DCONFIG_MCUBOOT_SIGNATURE_KEY_FILE="bootloader/mcuboot/root-rsa-2048.pem"' \
   -DEXTRA_CONF_FILE=overlay-permanent-download.conf


The listing below shows the output to the console when downloading via dfu-util.
Note the ``Swap type: perm``.

.. code-block:: console

   *** Booting Zephyr OS build zephyr-v3.0.0-361-ge6900e2451d5  ***
   [00:00:00.005,920] <inf> main: This device supports USB DFU class.

   *** Booting Zephyr OS build zephyr-v3.0.0-360-gc0dd594d4d3d  ***
   I: Starting bootloader
   I: Primary image: magic=good, swap_type=0x4, copy_done=0x1, image_ok=0x1
   I: Secondary image: magic=good, swap_type=0x3, copy_done=0x3, image_ok=0x1
   I: Boot source: none
   I: Swap type: perm
   I: Bootloader chainload address offset: 0xc000
   I: Jumping to the first image slot
   *** Booting Zephyr OS build zephyr-v3.0.0-361-gb987e6daa2f9  ***
   Hello World! nrf52840dk_nrf52840


.. _MCUboot GitHub repo: https://github.com/zephyrproject-rtos/mcuboot
.. _Using MCUboot with Zephyr: https://docs.mcuboot.com/readme-zephyr