USB Driver
==========

Overview
--------

The driver allows users to use {IDF_TARGET_NAME} chips to develop USB devices on top the TinyUSB stack. TinyUSB is integrating with ESP-IDF to provide USB features of the framework. Using this driver the chip works as a composite device supporting to represent several USB devices simultaneously. Currently, only the communications device class (CDC) type of the device with the ACM (Abstract Control Model) subclass is supported.


Features
--------

- Configuration of device and string USB descriptors
- USB Serial Device (CDC-ACM)
- Input and output through USB Serial Device


Hardware USB Connection
-----------------------

- Any board with the {IDF_TARGET_NAME} chip with USB connectors or with exposed USB's D+ and D- (DATA+/DATA-) pins.

If the board has no USB connector but has the pins, connect pins directly to the host (e.g. with do-it-yourself cable from any USB connection cable). For example, connect GPIO19/20 to D-/D+ respectively for an ESP32-S2 board:


.. figure:: ../../../_static/usb-board-connection.png
    :align: center
    :alt: Connection of a board to a host ESP32-S2
    :figclass: align-center

Driver Structure
----------------

As the basis is used the TinyUSB stack.

On top of it the driver implements:

- Customization of USB descriptors
- Serial device support
- Redirecting of standard streams through the Serial device
- Encapsulated driver's task servicing the TinyuSB



Configuration
-------------

Via Menuconfig options you can specify:

- Several of descriptor's parameters (see: Descriptors Configuration bellow)
- USB Serial low-level Configuration
- The verbosity of the TinyUSB's log
- Disable the TinyUSB main task (for the custom implementation)


Descriptors Configuration
^^^^^^^^^^^^^^^^^^^^^^^^^

The driver's descriptors are provided by the :cpp:type:`tinyusb_config_t` structure's :cpp:member:`descriptor` and :cpp:member:`string_descriptor` members. Therefore, users should initialize :cpp:type:`tinyusb_config_t` to their desired descriptor before calling :cpp:func:`tinyusb_driver_install` to install driver.

However, the driver also provides a default descriptor. The driver can be installed with the default descriptor by setting the :cpp:member:`descriptor` and :cpp:member:`string_descriptor` members of :cpp:type:`tinyusb_config_t` to `NULL` before calling :cpp:func:`tinyusb_driver_install`. The driver's default descriptor is specified using Menuconfig, where the following fields should be configured:

- PID
- VID
- bcdDevice
- Manufacturer
- Product name
- Name of CDC device if it is On
- Serial number

If you want to use own descriptors with extended modification, you can define them during the driver installation process


Install Driver
--------------
To initialize the driver, users should call :cpp:func:`tinyusb_driver_install`. The driver's configuration is specified in a :cpp:type:`tinyusb_config_t` structure that is passed as an argument to :cpp:func:`tinyusb_driver_install`.

 Note that the :cpp:type:`tinyusb_config_t` structure can be zero initialized (e.g. ``tinyusb_config_t tusb_cfg = { 0 }``) or partially (as shown below). For any member that is initialized to `0` or `NULL`, the driver will use its default configuration values for that member (see example below)

.. code-block:: c

    tinyusb_config_t partial_init = {
        .descriptor = NULL;         //Uses default descriptor specified in Menuconfig
        .string_descriptor = NULL;  //Uses default string specified in Menuconfig
        .external_phy = false;
    }

USB Serial Device (CDC-ACM)
---------------------------

If the CDC option is enabled in Menuconfig, the USB Serial Device could be initialized with :cpp:func:`tusb_cdc_acm_init` according to the settings from :cpp:type:`tinyusb_config_cdcacm_t` (see example below).

.. code-block:: c

    tinyusb_config_cdcacm_t amc_cfg = {
        .usb_dev = TINYUSB_USBDEV_0,
        .cdc_port = TINYUSB_CDC_ACM_0,
        .rx_unread_buf_sz = 64,
        .callback_rx = NULL,
        .callback_rx_wanted_char = NULL,
        .callback_line_state_changed = NULL,
        .callback_line_coding_changed = NULL
    };
    tusb_cdc_acm_init(&amc_cfg);

To specify callbacks you can either set the pointer to your :cpp:type:`tusb_cdcacm_callback_t` function in the configuration structure or call :cpp:func:`tinyusb_cdcacm_register_callback` after initialization.

USB Serial Console
^^^^^^^^^^^^^^^^^^

The driver allows to redirect all standard application strings (stdin/out/err) to the USB Serial Device and return them to UART using :cpp:func:`esp_tusb_init_console`/:cpp:func:`esp_tusb_deinit_console` functions.


Application Examples
--------------------

The table below describes the code examples available in the directory :example:`peripherals/usb/`.

.. list-table::
   :widths: 35 65
   :header-rows: 1

   * - Code Example
     - Description
   * - :example:`peripherals/usb/tusb_console`
     - How to set up {IDF_TARGET_NAME} chip to get log output via Serial Device connection
   * - :example:`peripherals/usb/tusb_sample_descriptor`
     - How to set up {IDF_TARGET_NAME} chip to work as a Generic USB Device with a user-defined descriptor
   * - :example:`peripherals/usb/tusb_serial_device`
     - How to set up {IDF_TARGET_NAME} chip to work as a USB Serial Device


API Reference
-------------

.. include-build-file:: inc/tinyusb.inc
.. include-build-file:: inc/tinyusb_types.inc
.. include-build-file:: inc/tusb_cdc_acm.inc
.. include-build-file:: inc/tusb_console.inc
.. include-build-file:: inc/tusb_tasks.inc
.. include-build-file:: inc/vfs_tinyusb.inc