DS3231 RTC with ESP32

Specifications

Power and logic levels

3.3 V: safe to connect directly

ESP32 pins, including those on a display board's connectors, work at 3.3 V and are not 5 V tolerant. Modules differ, so if in doubt, measure the signal before you connect it.

Wiring

Arduino code

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

const int SDA_PIN = 8, SCL_PIN = 9;   // use your board's I2C pins
RTC_DS3231 rtc;

void setup() {
  Serial.begin(115200);
  Wire.begin(SDA_PIN, SCL_PIN);
  if (!rtc.begin(&Wire)) {
    Serial.println("DS3231 not found");
    while (true) delay(1000);
  }
  if (rtc.lostPower()) rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
}

void loop() {
  DateTime n = rtc.now();
  Serial.printf("%04d-%02d-%02d %02d:%02d:%02d\n", n.year(), n.month(), n.day(), n.hour(), n.minute(), n.second());
  delay(1000);
}

Needs the RTClib library. Compiled for ESP32-S3 with arduino-esp32 3.x. Not yet tested by us on a physical sensor. Change the pins to match your board.

On a display

Read the value in your sketch and pass it to a label, or send it over MQTT and show it with an MQTT value in the editor.

Boards with a ready connector

Only boards whose connectors we have surveyed. Others may still work on free GPIOs.

Good to know

• Address 0x68 clashes with MPU6050 by default.
• Some cheap modules charge the cell. Do not charge a CR2032.
• With Wi-Fi available, NTP may be all you need.
• Some boards already have an RTC chip.

What it is good for

• Clocks without Wi-Fi
• Timers and schedules
• Data logging with timestamps

FAQ

Sources

• https://www.digikey.nl/nl/htmldatasheets/production/1799/0/0/1/ds3231s-.html

Related parts

• MPU6050
• BME280