Device Firmware Upgrade via USB
========================================

:link_to_translation:`zh_CN:[中文]`

Typically, the firmware of the {IDF_TARGET_NAME} is flashed via the chip's serial port. However, flashing via the serial port requires a USB to serial converter chip (e.g., CP210x or FTDI) to be connected to the {IDF_TARGET_NAME} (see :doc:`Establish Serial Connection with {IDF_TARGET_NAME} <../get-started/establish-serial-connection>` for more details). The {IDF_TARGET_NAME} contains a USB OTG peripheral making it possible to connect the {IDF_TARGET_NAME} to the host directly via USB (thus not requiring a USB to serial converter chip).

Device Firmware Upgrade (DFU) is a mechanism for upgrading the firmware of the {IDF_TARGET_NAME} directly via the Universal Serial Bus (USB).

- :ref:`get-started-get-prerequisites` of the Getting Started Guide introduces the software requirements of DFU.
- Section :ref:`api_guide_dfu_build` describes how to build firmware for DFU with ESP-IDF.
- Section :ref:`api_guide_dfu_flash` deals with flashing the firmware.

USB Connection
--------------

The necessary connections for the {IDF_TARGET_NAME}'s internal USB PHY (transceiver) are shown in the following table:

.. list-table::
   :header-rows: 1
   :widths: 25 20

   * - GPIO
     - USB

   * - 20
     - D+ (green)

   * - 19
     - D- (white)

   * - GND
     - GND (black)

   * - +5V
     - +5V (red)

.. warning::

    Some cables are wired up with non-standard colors and some drivers are able to work with swapped D+ and D- connections. Please try to swap the cables connecting to D+ and D- if your device is not detected.

.. only:: esp32s3

    By default, the :doc:`USB_SERIAL_JTAG<usb-serial-jtag-console>` module is connected to the {IDF_TARGET_NAME}'s internal USB PHY, while the USB OTG peripheral can be used only if an external USB PHY is connected. Since DFU is provided via the USB OTG peripheral, it cannot be used through the internal PHY in this configuration.

    However, users can permanently switch the internal USB PHY to work with USB OTG peripheral instead of USB_SERIAL_JTAG by burning the ``USB_PHY_SEL`` eFuse. See *{IDF_TARGET_NAME} Technical Reference Manual* [`PDF <{IDF_TARGET_TRM_EN_URL}>`__] for more details about USB_SERIAL_JTAG and USB OTG.

.. note::

    The {IDF_TARGET_NAME} chip needs to be in bootloader mode before it can be detected as a DFU device and flash. This can be achieved by pulling GPIO0 down (e.g., pressing the BOOT button), pulling RESET down for a moment, and releasing GPIO0.


.. _api_guide_dfu_build:

Building the DFU Image
======================

The command below will create a DFU image named ``dfu.bin`` that is placed in the project's ``build`` directory::

    idf.py dfu

.. note::
    Do not forget to set the target chip by ``idf.py set-target`` before running ``idf.py dfu``. Otherwise, you might create an image for a different chip or receive an error message like ``unknown target 'dfu'``.

.. _api_guide_dfu_flash:

Flashing the DFU Image
====================================

The command below will download the DFU image into the {IDF_TARGET_NAME}::

    idf.py dfu-flash

The command relies on `dfu-util <http://dfu-util.sourceforge.net/>`_. Please see :ref:`get-started-get-prerequisites` for installing ``dfu-util``. ``dfu-util`` needs additional setup for :ref:`api_guide_dfu_flash_win` or setting up an :ref:`api_guide_dfu_flash_udev`. macOS users should be able to use ``dfu-util`` without further setup.

If there are more boards with the same chip connected then ``idf.py dfu-list`` can be used to list the available devices, for example::

    Found Runtime: [303a:0002] ver=0723, devnum=4, cfg=1, intf=2, path="1-10", alt=0, name="UNKNOWN", serial="0"
    Found Runtime: [303a:0002] ver=0723, devnum=6, cfg=1, intf=2, path="1-2", alt=0, name="UNKNOWN", serial="0"

Consequently, the desired device can be selected for flashing by the ``--path`` argument. For example, the devices listed above can be flashed individually by the following commands::

    idf.py dfu-flash --path 1-10
    idf.py dfu-flash --path 1-2

.. note::
    The vendor and product identificators are set based on the selected chip target by the ``idf.py set-target`` command and they are not selectable during the ``idf.py dfu-flash`` call.

See :ref:`api_guide_dfu_flash_errors` and their solutions.

.. _api_guide_dfu_flash_udev:

Udev Rule (Linux only)
----------------------

Udev is a device manager for the Linux kernel. It allows us to run ``dfu-util`` (and ``idf.py dfu-flash``) without ``sudo`` for gaining access to the chip.

Create file ``/etc/udev/rules.d/40-dfuse.rules`` with the following content::

    SUBSYSTEMS=="usb", ATTRS{idVendor}=="303a", ATTRS{idProduct}=="00??", GROUP="plugdev", MODE="0666"

.. note::
    Please check the output of the command ``groups``. The user has to be a member of the `GROUP` specified above. You may use some other existing groups for this purpose (e.g., `uucp` on some systems instead of `plugdev`) or create a new group for this purpose.

Restart your computer so the previous setting could take into affect or run ``sudo udevadm trigger`` to force manually udev to trigger your new rule.

.. _api_guide_dfu_flash_win:

USB Drivers (Windows only)
--------------------------

``dfu-util`` uses `libusb` to access the device. You have to register on Windows the device with the `WinUSB` driver.

Please see the `libusb wiki <https://github.com/libusb/libusb/wiki/Windows#How_to_use_libusb_on_Windows>`_ for more details.

The drivers can be installed by the `Zadig tool <https://zadig.akeo.ie/>`_. Please make sure that the device is in download mode before you run the tool and that it detects the {IDF_TARGET_NAME} device before you install the drivers. The Zadig tool might detect several USB interfaces of {IDF_TARGET_NAME}. Please install the WinUSB driver only for the interface where there is no driver installed (probably it is Interface 2) and do not re-install the driver for the other interface.

.. warning::
    The manual installation of the driver in Device Manager of Windows is not recommended because the flashing might not work properly.

.. _api_guide_dfu_flash_errors:

Common Errors and Known Issues
------------------------------

- ``dfu-util: command not found`` might indicate that the tool hasn't been installed or is not available from the terminal. An easy way of checking the tool is running ``dfu-util --version``. Please see :ref:`get-started-get-prerequisites` for installing ``dfu-util``.

- The reason for ``No DFU capable USB device available`` could be that the USB driver wasn't properly installed on Windows (see :ref:`api_guide_dfu_flash_win`), udev rule was not setup on Linux (see :ref:`api_guide_dfu_flash_udev`) or the device isn't in bootloader mode.

- Flashing with ``dfu-util`` on Windows fails on the first attempt with error ``Lost device after RESET?``. Please retry the flashing and it should succeed the next time.
