Introduction
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The datasheet for the DS3231 explains that this part is an
"Extremely Accurate I²C-Integrated RTC/TCXO/Crystal". And,
hey, it does exactly what it says on the tin! This Real Time
Clock (RTC) is the most precise you can get in a small, low
power package.
Most RTCs use an external 32kHz timing crystal that is used
to keep time with low current draw. And that's all well and
good, but those crystals have slight drift, particularly when
the temperature changes (the temperature changes the oscillation
frequency very very very slightly but it does add up!) This
RTC is in a beefy package because the crystal is inside the
chip! And right next to the integrated crystal is a temperature
sensor. That sensor compensates for the frequency changes by
adding or removing clock ticks so that the timekeeping stays
on schedule.
This is the finest RTC you can get, and now we have it in a
compact, breadboard-friendly breakout. With a coin cell
plugged into the back, you can get years of precision
timekeeping, even when main power is lost. Great for
datalogging and clocks, or anything where you need to
really know the time.
.. image:: ../docs/_static/3013-01.jpg
:alt: DS3231 Product Image
Dependencies
This driver depends on:
Adafruit CircuitPython <https://github.com/adafruit/circuitpython>
_Bus Device <https://github.com/adafruit/Adafruit_CircuitPython_BusDevice>
_Register <https://github.com/adafruit/Adafruit_CircuitPython_Register>
_
Please ensure all dependencies are available on the CircuitPython filesystem.
This is easily achieved by downloading
the Adafruit library and driver bundle <https://github.com/adafruit/Adafruit_CircuitPython_Bundle>
_.
Installing from PyPI
On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI <https://pypi.org/project/adafruit-circuitpython-ds3231/>
_. To install for current user:
.. code-block:: shell
pip3 install adafruit-circuitpython-ds3231
To install system-wide (this may be required in some cases):
.. code-block:: shell
sudo pip3 install adafruit-circuitpython-ds3231
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 adafruit-circuitpython-ds3231
Usage Notes
Basics
Of course, you must import the library to use it:
.. code:: python3
import adafruit_ds3231
import time
All the Adafruit 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() # uses board.SCL and board.SDA
Once you have created the I2C interface object, you can use it to instantiate
the RTC object:
.. code:: python3
rtc = adafruit_ds3231.DS3231(i2c)
Date and time
To set the time, you need to set datetime
to a time.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 alarm1
or alarm2
to a tuple with a
time.struct_time
object and string representing the frequency such as "hourly":
.. code:: python3
rtc.alarm1 = (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 corresponding
alarm1_status
or alarm2_status
attributes. Once True, set it back to False
to reset.
.. code:: python3
if rtc.alarm1_status:
print("wake up!")
rtc.alarm1_status = False
Documentation
API documentation for this library can be found on Read the Docs <https://docs.circuitpython.org/projects/ds3231/en/latest/>
_.
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! Please read our Code of Conduct <https://github.com/adafruit/Adafruit_CircuitPython_DS3231/blob/main/CODE_OF_CONDUCT.md>
_
before contributing to help this project stay welcoming.