:mod:`rtc`
==========

.. py:module:: rtc

.. autoapi-nested-parse::

   Real Time Clock

   The `rtc` module provides support for a Real Time Clock. You can access and manage the
   RTC using :class:`rtc.RTC`. It also backs the :func:`time.time` and :func:`time.localtime`
   functions using the onboard RTC if present.



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.. py:function:: set_time_source(rtc: RTC) -> None

   Sets the RTC time source used by :func:`time.localtime`.
   The default is :class:`rtc.RTC`, but it's useful to use this to override the
   time source for testing purposes. For example::

     import rtc
     import time

     class RTC(object):
         @property
         def datetime(self):
             return time.struct_time((2018, 3, 17, 21, 1, 47, 0, 0, 0))

     r = RTC()
     rtc.set_time_source(r)


.. py:class:: RTC

   Real Time Clock

   This class represents the onboard Real Time Clock. It is a singleton and will always return the same instance.

   .. py:attribute:: datetime
      :annotation: :time.struct_time

      The current date and time of the RTC as a `time.struct_time`.

      This must be set to the current date and time whenever the board loses power::

        import rtc
        import time

        r = rtc.RTC()
        r.datetime = time.struct_time((2019, 5, 29, 15, 14, 15, 0, -1, -1))


      Once set, the RTC will automatically update this value as time passes. You can read this
      property to get a snapshot of the current time::

        current_time = r.datetime
        print(current_time)
        # struct_time(tm_year=2019, tm_month=5, ...)


   .. py:attribute:: calibration
      :annotation: :int

      The RTC calibration value as an `int`.

      A positive value speeds up the clock and a negative value slows it down.
      Range and value is hardware specific, but one step is often approximately 1 ppm::

        import rtc
        import time

        r = rtc.RTC()
        r.calibration = 1