Documentation

// DS3231 RTC - Arduino Example
// Library: RTClib by Adafruit

#include <Wire.h>
#include <RTClib.h>

RTC_DS3231 rtc;

void setup() {
  Serial.begin(9600);
  if (!rtc.begin()) {
    Serial.println("DS3231 not found!");
    while (1);
  }

  // Run ONCE to set time, then comment out and re-upload:
  // rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));

  if (rtc.lostPower()) {
    Serial.println("Setting time to compile time...");
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }
}

void loop() {
  DateTime now = rtc.now();

  Serial.print(now.year()); Serial.print('/');
  Serial.print(now.month()); Serial.print('/');
  Serial.print(now.day()); Serial.print(' ');
  Serial.print(now.hour()); Serial.print(':');
  Serial.print(now.minute()); Serial.print(':');
  Serial.println(now.second());

  Serial.print("Temp: ");
  Serial.print(rtc.getTemperature());
  Serial.println(" C");

  delay(1000);
}

#!/usr/bin/env python3
# Install: pip install adafruit-circuitpython-ds3231
# Enable I2C: sudo raspi-config

import time
import board, busio
import adafruit_ds3231

i2c = busio.I2C(board.SCL, board.SDA)
rtc = adafruit_ds3231.DS3231(i2c)

# Set time once (uncomment, run, then re-comment):
# t = time.struct_time((2026, 5, 3, 12, 0, 0, 0, -1, -1))
# rtc.datetime = t

while True:
    t = rtc.datetime
    print(f"{t.tm_year}-{t.tm_mon:02d}-{t.tm_mday:02d} "
          f"{t.tm_hour:02d}:{t.tm_min:02d}:{t.tm_sec:02d}")
    print(f"Temp: {rtc.temperature:.2f} C")
    time.sleep(1)

# DS3231 on Pico - MicroPython
# Save ds3231_micropython.py from the micropython-stubs repo, or use this minimal driver

from machine import I2C, Pin
import time

I2C_ADDR = 0x68
i2c = I2C(0, sda=Pin(4), scl=Pin(5), freq=400000)

def bcd2dec(b):
    return (b // 16) * 10 + (b % 16)
def dec2bcd(d):
    return (d // 10) * 16 + (d % 10)

def get_time():
    data = i2c.readfrom_mem(I2C_ADDR, 0x00, 7)
    sec = bcd2dec(data[0] & 0x7F)
    minute = bcd2dec(data[1])
    hour = bcd2dec(data[2] & 0x3F)
    day = bcd2dec(data[4])
    month = bcd2dec(data[5] & 0x1F)
    year = 2000 + bcd2dec(data[6])
    return (year, month, day, hour, minute, sec)

while True:
    print(get_time())
    time.sleep(1)