The Dallas DS3231M Real Time Clock is a compact high precision real time clock module that comes in a SOIC-8 surface mount package. It runs on 2.3V to 5.5V supply voltage and is controlled using the I2C/TWI protocol. It features two hardware alarms with interrupt, so you can use it to make your microcontroller do tasks at specific times. Combined with sleep mode this makes a perfect companion for creating a logging module.

We've prepared a breakout board that comes with a backup battery and gives access to all the features of the RTC (including interrupt pin and 32kHz square wave output). We also provide an Arduino (as well as avr-gcc) library that supports all features of the chip.


  • DS3231M high precision Real Time Clock
  • Backup battery
  • Very compact PCB
  • Two TWI/I2C ports to daisy chain with other TWI/I2C devices
  • Open Source Arduino and low-level avr-gcc library available on Github
  • Pull-up resistors for SDA/SCL as well as for the 32KHz oscillator and square wave ouptut/alarm interrupt output