:mod:`pwmio`
============

.. py:module:: pwmio

.. autoapi-nested-parse::

   Support for PWM based protocols

   The `pwmio` module contains classes to provide access to basic pulse IO.

   All classes change hardware state and should be deinitialized when they
   are no longer needed if the program continues after use. To do so, either
   call :py:meth:`!deinit` or use a context manager. See
   :ref:`lifetime-and-contextmanagers` for more info.

   For example::

     import time
     import pwmio
     import board

     pwm = pwmio.PWMOut(board.LED)
     pwm.duty_cycle = 2 ** 15
     time.sleep(0.1)

   This example will initialize the the device, set
   :py:data:`~pwmio.PWMOut.duty_cycle`, and then sleep 0.1 seconds.
   CircuitPython will automatically turn off the PWM when it resets all
   hardware after program completion. Use ``deinit()`` or a ``with`` statement
   to do it yourself.



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.. py:class:: PWMOut(pin: microcontroller.Pin, *, duty_cycle: int = 0, frequency: int = 500, variable_frequency: bool = False)

   Output a Pulse Width Modulated signal on a given pin.

   Create a PWM object associated with the given pin. This allows you to
   write PWM signals out on the given pin. Frequency is fixed after init
   unless ``variable_frequency`` is True.

   .. note:: When ``variable_frequency`` is True, further PWM outputs may be
     limited because it may take more internal resources to be flexible. So,
     when outputting both fixed and flexible frequency signals construct the
     fixed outputs first.

   :param ~microcontroller.Pin pin: The pin to output to
   :param int duty_cycle: The fraction of each pulse which is high. 16-bit
   :param int frequency: The target frequency in Hertz (32-bit)
   :param bool variable_frequency: True if the frequency will change over time


   Simple LED on::

     import pwmio
     import board

     pwm = pwmio.PWMOut(board.LED)

     while True:
         pwm.duty_cycle = 2 ** 15  # Cycles the pin with 50% duty cycle (half of 2 ** 16) at the default 500hz

   PWM LED fade::

     import pwmio
     import board

     pwm = pwmio.PWMOut(board.LED)  # output on LED pin with default of 500Hz

     while True:
         for cycle in range(0, 65535):  # Cycles through the full PWM range from 0 to 65535
             pwm.duty_cycle = cycle  # Cycles the LED pin duty cycle through the range of values
         for cycle in range(65534, 0, -1):  # Cycles through the PWM range backwards from 65534 to 0
             pwm.duty_cycle = cycle  # Cycles the LED pin duty cycle through the range of values

   PWM at specific frequency (servos and motors)::

     import pwmio
     import board

     pwm = pwmio.PWMOut(board.D13, frequency=50)
     pwm.duty_cycle = 2 ** 15  # Cycles the pin with 50% duty cycle (half of 2 ** 16) at 50hz

   Variable frequency (usually tones)::

     import pwmio
     import board
     import time

     pwm = pwmio.PWMOut(board.D13, duty_cycle=2 ** 15, frequency=440, variable_frequency=True)
     time.sleep(0.2)
     pwm.frequency = 880
     time.sleep(0.1)

   .. py:attribute:: duty_cycle
      :annotation: :int

      16 bit value that dictates how much of one cycle is high (1) versus low
      (0). 0xffff will always be high, 0 will always be low and 0x7fff will
      be half high and then half low.

      Depending on how PWM is implemented on a specific board, the internal
      representation for duty cycle might have less than 16 bits of resolution.
      Reading this property will return the value from the internal representation,
      so it may differ from the value set.


   .. py:attribute:: frequency
      :annotation: :int

      32 bit value that dictates the PWM frequency in Hertz (cycles per
      second). Only writeable when constructed with ``variable_frequency=True``.

      Depending on how PWM is implemented on a specific board, the internal value
      for the PWM's duty cycle may need to be recalculated when the frequency
      changes. In these cases, the duty cycle is automatically recalculated
      from the original duty cycle value. This should happen without any need
      to manually re-set the duty cycle.


   .. py:method:: deinit() -> None

      Deinitialises the PWMOut and releases any hardware resources for reuse.


   .. py:method:: __enter__() -> PWMOut

      No-op used by Context Managers.


   .. py:method:: __exit__() -> None

      Automatically deinitializes the hardware when exiting a context. See
      :ref:`lifetime-and-contextmanagers` for more info.