How to Use RTC DS3231: Examples, Pinouts, and Specs

The Real-Time Clock (RTC) DS3231 is a low-cost, extremely accurate I2C real-time clock with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input, and maintains accurate timekeeping when main power to the device is interrupted. The integration of the crystal resonator enhances the long-term accuracy of the device and reduces the piece-part count in a manufacturing line. Common applications of the DS3231 include timekeeping for embedded systems, network servers, data loggers, and other devices that require precise time stamping.

• Time Accuracy: ±2ppm from 0°C to +40°C
• Battery Backup Input: 2.3V to 5.5V
• Operating Voltage: 2.3V to 5.5V
• Operating Temperature: -40°C to +85°C
• Digital Temp Sensor Output: ±3°C accuracy
• Memory: 236 bytes of non-volatile RAM

To use the DS3231 with an Arduino, connect the following pins:

• DS3231 SCL to Arduino A5 (or the SCL pin for your specific Arduino)
• DS3231 SDA to Arduino A4 (or the SDA pin for your specific Arduino)
• DS3231 VCC to Arduino 5V
• DS3231 GND to Arduino GND
• Optionally, DS3231 32K to an input pin if you need a 32kHz signal
• Optionally, DS3231 SQW to an interrupt pin if you need a square wave or alarm interrupt

• Always connect the battery to the DS3231 to ensure timekeeping during power outages.
• Avoid placing heat-generating components near the DS3231 to prevent temperature-induced inaccuracies.
• Use pull-up resistors on the SDA and SCL lines if your Arduino board does not have them built-in.

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

RTC_DS3231 rtc;

void setup() {
  Serial.begin(9600);
  if (!rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }

  if (rtc.lostPower()) {
    Serial.println("RTC lost power, let's set the time!");
    // The following line sets the RTC to the date & time this sketch was compiled
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }
}

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

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

  delay(1000);
}

• Time Not Accurate: Ensure the battery is properly installed and charged.
• No Communication: Check the SDA and SCL connections and ensure pull-up resistors are in place.
• Device Not Found: Make sure the DS3231 is powered and the correct I2C address is being used in your code.

• If the time drifts significantly, replace the battery and reset the time.
• Use the I2C scanner sketch to check if the Arduino is detecting the DS3231.
• Ensure the Arduino library for the DS3231 is correctly installed and included in your sketch.

Q: Can the DS3231 be used in battery-powered applications? A: Yes, the DS3231 is suitable for battery-powered applications due to its low power consumption.

Q: What is the purpose of the 32K pin? A: The 32K pin outputs a 32.768kHz signal that can be used to drive a microcontroller timer or as a clock reference.

Q: How do I set alarms on the DS3231? A: Alarms can be set using the RTC library functions. Refer to the library documentation for specific instructions.

Q: What is the battery life expectancy when using the DS3231? A: Battery life depends on the type of battery used and the environmental conditions but typically lasts for 2+ years with a standard 3V lithium cell.