Introduction to the PCF85063A Real Time Clock (RTC) Library

This is a super-small real time clock (RTC) that allows your microcontroller project to keep track of time even if it is reprogrammed, or if the power is lost. Perfect for datalogging, clock-building, time stamping, timers and alarms, etc.

The PCF85063A is simple and inexpensive but not a high precision device. It may lose or gain up to two seconds a day. For a high-precision, temperature compensated alternative, please check out the DS3231 precision RTC. <https://www.adafruit.com/products/3013>_ If you need a DS1307 for compatibility reasons, check out our DS1307 RTC breakout <https://www.adafruit.com/products/3296>_.

The PCF85063A is used in various Pimoroni boards, e.g. the Badger2040W or InkyFrame. It is also used in the CM4IO-board.

Dependencies

This driver depends on the Register <https://github.com/adafruit/Adafruit_CircuitPython_Register>_ and Bus Device <https://github.com/adafruit/Adafruit_CircuitPython_BusDevice>_ libraries. Please ensure they are also available on the CircuitPython filesystem. This is easily achieved by downloading a library and driver bundle <https://github.com/adafruit/Adafruit_CircuitPython_Bundle>_.

Installing from PyPI

Note: currently, the package is not yet available from PyPI.

On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI <https://pypi.org/project/circuitpython-pcf85063a/>_. To install for current user:

.. code-block:: shell

pip3 install circuitpython-pcf85063a

To install system-wide (this may be required in some cases):

.. code-block:: shell

sudo pip3 install circuitpython-pcf85063a

To install in a virtual environment in your current project:

.. code-block:: shell

mkdir project-name && cd project-name
python3 -m venv .venv
source .venv/bin/activate
pip3 install circuitpython-pcf85063a

Usage Notes

Basics

Of course, you must import the library to use it:

.. code:: python3

import time
import pcf85063a

All the RTC libraries take an instantiated and active I2C object (from the board library) as an argument to their constructor. The way to create an I2C object depends on the board you are using. For boards with labeled SCL and SDA pins, you can:

.. code:: python3

import board

Now, to initialize the I2C bus:

.. code:: python3

i2c = board.I2C()

Once you have created the I2C interface object, you can use it to instantiate the RTC object:

.. code:: python3

rtc = pcf85063a.PCF85063A(i2c)

Date and time

To set the time, you need to set datetimeto atime.struct_time` object:

.. code:: python3

rtc.datetime = time.struct_time((2017,1,9,15,6,0,0,9,-1))

After the RTC is set, you retrieve the time by reading the datetime attribute and access the standard attributes of a struct_time such as tm_year, tm_hour and tm_min.

.. code:: python3

t = rtc.datetime
print(t)
print(t.tm_hour, t.tm_min)

Alarm

To set the time, you need to set alarm to a tuple with a time.struct_time object and string representing the frequency such as "hourly":

.. code:: python3

rtc.alarm = (time.struct_time((2017,1,9,15,6,0,0,9,-1)), "daily")

After the RTC is set, you retrieve the alarm status by reading the alarm_status attribute. Once True, set it back to False to reset.

.. code:: python3

if rtc.alarm_status:
    print("wake up!")
    rtc.alarm_status = False

Documentation

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>_.

Contributing

Contributions are welcome! This project follows Adafruit's Code of Conduct <https://github.com/bablokb/circuitpython_pcf85063a/blob/main/CODE_OF_CONDUCT.md>_ before contributing to help this project stay welcoming.