circuitpython/docs/library/pyb.RTC.rst

84 lines
2.4 KiB
ReStructuredText
Raw Normal View History

.. currentmodule:: pyb
.. _pyb.RTC:
2014-10-31 18:21:37 -04:00
class RTC -- real time clock
============================
The RTC is and independent clock that keeps track of the date
and time.
Example usage::
rtc = pyb.RTC()
rtc.datetime((2014, 5, 1, 4, 13, 0, 0, 0))
print(rtc.datetime())
Constructors
------------
.. class:: pyb.RTC()
Create an RTC object.
Methods
-------
.. method:: RTC.datetime([datetimetuple])
Get or set the date and time of the RTC.
With no arguments, this method returns an 8-tuple with the current
date and time. With 1 argument (being an 8-tuple) it sets the date
and time.
.. only:: port_pyboard
The 8-tuple has the following format:
(year, month, day, weekday, hours, minutes, seconds, subseconds)
``weekday`` is 1-7 for Monday through Sunday.
``subseconds`` counts down from 255 to 0
.. only:: port_pyboard
.. method:: RTC.wakeup(timeout, callback=None)
Set the RTC wakeup timer to trigger repeatedly at every ``timeout``
milliseconds. This trigger can wake the pyboard from both the sleep
states: :meth:`pyb.stop` and :meth:`pyb.standby`.
If ``timeout`` is ``None`` then the wakeup timer is disabled.
If ``callback`` is given then it is executed at every trigger of the
wakeup timer. ``callback`` must take exactly one argument.
.. method:: RTC.info()
Get information about the startup time and reset source.
- The lower 0xffff are the number of milliseconds the RTC took to
start up.
- Bit 0x10000 is set if a power-on reset occurred.
- Bit 0x20000 is set if an external reset occurred
.. method:: RTC.calibration(cal)
Get or set RTC calibration.
With no arguments, ``calibration()`` returns the current calibration
value, which is an integer in the range [-511 : 512]. With one
argument it sets the RTC calibration.
2016-07-31 19:52:00 -04:00
The RTC Smooth Calibration mechanism adjusts the RTC clock rate by
adding or subtracting the given number of ticks from the 32768 Hz
clock over a 32 second period (corresponding to 2^20 clock ticks.)
Each tick added will speed up the clock by 1 part in 2^20, or 0.954
ppm; likewise the RTC clock it slowed by negative values. The
usable calibration range is:
(-511 * 0.954) ~= -487.5 ppm up to (512 * 0.954) ~= 488.5 ppm