:mod:`usb_midi`
===============

.. py:module:: usb_midi

.. autoapi-nested-parse::

   MIDI over USB

   The `usb_midi` module contains classes to transmit and receive MIDI messages over USB.



.. raw:: html

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    </p>




.. py:data:: ports
   :annotation: :Tuple[Union[PortIn, PortOut], Ellipsis]

   Tuple of all MIDI ports. Each item is ether `PortIn` or `PortOut`.


.. py:function:: disable() -> None

   Disable presenting a USB MIDI device to the host.
   The device is normally enabled by default, but on some boards with limited endpoints
   including ESP32-S2 and certain STM boards, it is disabled by default.
   Can be called in ``boot.py``, before USB is connected.


.. py:function:: enable() -> None

   Enable presenting a USB MIDI device to the host.
   The device is enabled by default, so you do not normally need to call this function.
   Can be called in ``boot.py``, before USB is connected.

   If you enable too many devices at once, you will run out of USB endpoints.
   The number of available endpoints varies by microcontroller.
   CircuitPython will go into safe mode after running boot.py to inform you if
   not enough endpoints are available.


.. py:class:: PortIn

   Receives midi commands over USB

   You cannot create an instance of `usb_midi.PortIn`.

   PortIn objects are constructed for every corresponding entry in the USB
   descriptor and added to the ``usb_midi.ports`` tuple.

   .. py:method:: read(nbytes: Optional[int] = None) -> Optional[bytes]

      Read characters.  If ``nbytes`` is specified then read at most that many
      bytes. Otherwise, read everything that arrives until the connection
      times out. Providing the number of bytes expected is highly recommended
      because it will be faster.

      :return: Data read
      :rtype: bytes or None


   .. py:method:: readinto(buf: _typing.WriteableBuffer, nbytes: Optional[int] = None) -> Optional[bytes]

      Read bytes into the ``buf``.  If ``nbytes`` is specified then read at most
      that many bytes.  Otherwise, read at most ``len(buf)`` bytes.

      :return: number of bytes read and stored into ``buf``
      :rtype: bytes or None



.. py:class:: PortOut

   Sends midi messages to a computer over USB

   You cannot create an instance of `usb_midi.PortOut`.

   PortOut objects are constructed for every corresponding entry in the USB
   descriptor and added to the ``usb_midi.ports`` tuple.

   .. py:method:: write(buf: _typing.ReadableBuffer) -> Optional[int]

      Write the buffer of bytes to the bus.

      :return: the number of bytes written
      :rtype: int or None