CircuitPython library to support DS3231 Real Time Clock (RTC).

This library supports the use of the DS3231-based RTC in CircuitPython.

Author(s): Philip R. Moyer and Radomir Dopieralski for Adafruit Industries.

Implementation Notes


Software and Dependencies:


  1. Milliseconds are not supported by this RTC.

  2. Datasheet:

class adafruit_ds3231.DS3231(i2c: I2C)[source]

Interface to the DS3231 RTC.


i2c (I2C) – The I2C bus the device is connected to

Quickstart: Importing and using the device

Here is an example of using the DS3231 class. First you will need to import the libraries to use the sensor

import time
import board
import adafruit_ds3231

Once this is done you can define your board.I2C object and define your sensor object

i2c = board.I2C()  # uses board.SCL and board.SDA
rtc = adafruit_ds3231.DS3231(i2c)

Now you can give the current time to the device.

t = time.struct_time((2017, 10, 29, 15, 14, 15, 0, -1, -1))
rtc.datetime = t

You can access the current time accessing the datetime attribute.

current_time = rtc.datetime

Alarm time for the first alarm.


True if the interrupt pin will output when alarm1 is alarming.


True if alarm1 is alarming. Set to False to reset.


Alarm time for the second alarm.


True if the interrupt pin will output when alarm2 is alarming.


True if alarm2 is alarming. Set to False to reset.

property calibration: int

Calibrate the frequency of the crystal oscillator by adding or removing capacitance. The datasheet calls this the Aging Offset. Calibration values range from -128 to 127; each step is approximately 0.1ppm, and positive values decrease the frequency (increase the period). When set, a temperature conversion is forced so the result of calibration can be seen directly at the 32kHz pin immediately

property datetime: struct_time

Gets the current date and time or sets the current date and time then starts the clock.


Current date and time.


True if the oscillator is disabled.

force_temperature_conversion() float[source]

Forces a conversion and returns the new temperature


True if the device has lost power since the time was set.

property temperature: float

Returns the last temperature measurement. Temperature is updated only every 64 seconds, or when a conversion is forced.