1  
  2  Introduction to Adafruit's PCF8523 Real Time Clock (RTC) Library
  3  ================================================================
  4  
  5  .. image:: https://readthedocs.org/projects/adafruit-circuitpython-pcf8523/badge/?version=latest
  6      :target: https://circuitpython.readthedocs.io/projects/pcf8523/en/latest/
  7      :alt: Documentation Status
  8  
  9  .. image :: https://img.shields.io/discord/327254708534116352.svg
 10      :target: https://adafru.it/discord
 11      :alt: Discord
 12  
 13  .. image:: https://github.com/adafruit/Adafruit_CircuitPython_PCF8523/workflows/Build%20CI/badge.svg
 14      :target: https://github.com/adafruit/Adafruit_CircuitPython_PCF8523/actions/
 15      :alt: Build Status
 16  
 17  This is a great battery-backed real time clock (RTC) that allows your
 18  microcontroller project to keep track of time even if it is reprogrammed,
 19  or if the power is lost. Perfect for datalogging, clock-building, time
 20  stamping, timers and alarms, etc. Equipped with PCF8523 RTC - it can
 21  run from 3.3V or 5V power & logic!
 22  
 23  The PCF8523 is simple and inexpensive but not a high precision device.
 24  It may lose or gain up to two seconds a day. For a high-precision,
 25  temperature compensated alternative, please check out the
 26  `DS3231 precision RTC. <https://www.adafruit.com/products/3013>`_
 27  If you need a DS1307 for compatibility reasons, check out our
 28  `DS1307 RTC breakout <https://www.adafruit.com/products/3296>`_.
 29  
 30  .. image:: _static/3295-00.jpg
 31      :alt: PCF8523 Breakout Board
 32  
 33  Dependencies
 34  =============
 35  
 36  This driver depends on the `Register <https://github.com/adafruit/Adafruit_CircuitPython_Register>`_
 37  and `Bus Device <https://github.com/adafruit/Adafruit_CircuitPython_BusDevice>`_
 38  libraries. Please ensure they are also available on the CircuitPython filesystem.
 39  This is easily achieved by downloading
 40  `a library and driver bundle <https://github.com/adafruit/Adafruit_CircuitPython_Bundle>`_.
 41  
 42  Installing from PyPI
 43  ====================
 44  On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally `from
 45  PyPI <https://pypi.org/project/adafruit-circuitpython-pcf8523/>`_. To install for current user:
 46  
 47  .. code-block:: shell
 48  
 49      pip3 install adafruit-circuitpython-pcf8523
 50  
 51  To install system-wide (this may be required in some cases):
 52  
 53  .. code-block:: shell
 54  
 55      sudo pip3 install adafruit-circuitpython-pcf8523
 56  
 57  To install in a virtual environment in your current project:
 58  
 59  .. code-block:: shell
 60  
 61      mkdir project-name && cd project-name
 62      python3 -m venv .env
 63      source .env/bin/activate
 64      pip3 install adafruit-circuitpython-pcf8523
 65  
 66  
 67  Usage Notes
 68  ===========
 69  
 70  Basics
 71  ------
 72  
 73  Of course, you must import the library to use it:
 74  
 75  .. code:: python
 76  
 77      import busio
 78      import adafruit_pcf8523
 79      import time
 80  
 81  All the Adafruit RTC libraries take an instantiated and active I2C object
 82  (from the `busio` library) as an argument to their constructor. The way to
 83  create an I2C object depends on the board you are using. For boards with labeled
 84  SCL and SDA pins, you can:
 85  
 86  .. code:: python
 87  
 88      from board import *
 89  
 90  You can also use pins defined by the onboard `microcontroller` through the
 91  `microcontroller.Pin` module.
 92  
 93  Now, to initialize the I2C bus:
 94  
 95  .. code:: python
 96  
 97      i2c_bus = busio.I2C(SCL, SDA)
 98  
 99  Once you have created the I2C interface object, you can use it to instantiate
100  the RTC object:
101  
102  .. code:: python
103  
104      rtc = adafruit_pcf8523.PCF8523(i2c_bus)
105  
106  Date and time
107  -------------
108  
109  To set the time, you need to set datetime` to a `time.struct_time` object:
110  
111  .. code:: python
112  
113      rtc.datetime = time.struct_time((2017,1,9,15,6,0,0,9,-1))
114  
115  After the RTC is set, you retrieve the time by reading the `datetime`
116  attribute and access the standard attributes of a struct_time such as ``tm_year``,
117  ``tm_hour`` and ``tm_min``.
118  
119  .. code:: python
120  
121      t = rtc.datetime
122      print(t)
123      print(t.tm_hour, t.tm_min)
124  
125  Alarm
126  -----
127  
128  To set the time, you need to set `alarm` to a tuple with a `time.struct_time`
129  object and string representing the frequency such as "hourly":
130  
131  .. code:: python
132  
133      rtc.alarm = (time.struct_time((2017,1,9,15,6,0,0,9,-1)), "daily")
134  
135  After the RTC is set, you retrieve the alarm status by reading the
136  `alarm_status` attribute. Once True, set it back to False to reset.
137  
138  .. code:: python
139  
140      if rtc.alarm_status:
141          print("wake up!")
142          rtc.alarm_status = False
143  
144  Contributing
145  ============
146  
147  Contributions are welcome! Please read our `Code of Conduct
148  <https://github.com/adafruit/Adafruit_CircuitPython_PCF8523/blob/master/CODE_OF_CONDUCT.md>`_
149  before contributing to help this project stay welcoming.
150  
151  Documentation
152  =============
153  
154  For information on building library documentation, please check out `this guide <https://learn.adafruit.com/creating-and-sharing-a-circuitpython-library/sharing-our-docs-on-readthedocs#sphinx-5-1>`_.