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.
This driver depends on:
Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle.
Of course, you must import the library to use it:
import busio import adafruit_ds3231 import time
All the Adafruit RTC libraries take an instantiated and active I2C object
busio 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:
from board import *
You can also use pins defined by the onboard
microcontroller through the
Now, to initialize the I2C bus:
myI2C = busio.I2C(SCL, SDA)
Once you have created the I2C interface object, you can use it to instantiate the RTC object:
rtc = adafruit_ds3231.DS3231(myI2C)
Date and time¶
To set the time, you need to set
datetime to a
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
attribute and access the standard attributes of a struct_time such as
t = rtc.datetime print(t) print(t.tm_hour, t.tm_min)
To set the time, you need to set
alarm2 to a tuple with a
time.struct_time object and string representing the frequency such as “hourly”:
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
alarm2_status attributes. Once True, set it back to False
if rtc.alarm1_status: print("wake up!") rtc.alarm1_status = False
Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.
To build this library locally you’ll need to install the circuitpython-build-tools package.
python3 -m venv .env source .env/bin/activate pip install circuitpython-build-tools
Once installed, make sure you are in the virtual environment:
Then run the build:
circuitpython-build-bundles --filename_prefix adafruit-circuitpython-ds3231 --library_location .
Sphinx is used to build the documentation based on rST files and comments in the code. First, install dependencies (feel free to reuse the virtual environment from above):
python3 -m venv .env source .env/bin/activate pip install Sphinx sphinx-rtd-theme
Now, once you have the virtual environment activated:
cd docs sphinx-build -E -W -b html . _build/html
This will output the documentation to
docs/_build/html. Open the index.html in your browser to
view them. It will also (due to -W) error out on any warning like Travis will. This is a good way to
locally verify it will pass.