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

The Adafruit DS3231 is a precision real-time clock (RTC) module that maintains accurate timekeeping even when the main power to the device it's connected to is turned off. Utilizing a temperature-compensated crystal oscillator, the DS3231 provides high stability and accuracy. Common applications include timekeeping in embedded systems, data logging with timestamps, and scheduling in various electronic projects.

• Time Accuracy: ±2ppm from 0°C to +40°C
• Battery Backup: Yes (CR2032 coin cell)
• Communication: I2C interface
• Operating Voltage: 2.3V to 5.5V
• Operating Temperature: -40°C to +85°C
• Memory: 236 bytes of non-volatile RAM

1. Power Connections: Connect VCC to a 2.3V to 5.5V power supply and GND to the ground.
2. I2C Connections: Connect SDA and SCL to your microcontroller's I2C data and clock lines respectively. For Arduino UNO, SDA is A4 and SCL is A5.
3. Battery Backup: Insert a CR2032 coin cell battery to keep the RTC running when main power is lost.
4. Square Wave/Interrupts: Optionally, use the SQW pin for generating square waves or as an interrupt signal.
5. 32kHz Output: Optionally, use the 32K pin if a 32kHz reference signal is required.

• Ensure that the I2C bus has pull-up resistors as required for your microcontroller.
• Avoid placing the module near heat sources to prevent temperature-induced inaccuracies.
• When using battery backup, be mindful of the battery's shelf life and replace it as needed.

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

RTC_DS3231 rtc;

void setup() {
  Serial.begin(9600);
  
  // Check if the RTC is connected correctly
  if (!rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }

  // Check if the RTC lost power and if so, set the time
  if (rtc.lostPower()) {
    Serial.println("RTC lost power, setting 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();
  
  // Print the current date and time
  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();
  
  // Wait for a second
  delay(1000);
}

• Time Not Accurate: Ensure the RTC module is not exposed to extreme temperatures and that the battery is in good condition.
• I2C Communication Failure: Check the wiring, ensure pull-up resistors are in place, and verify that the correct I2C address is being used.
• Module Not Responding: Make sure the power supply is within the specified range and the battery is properly installed.

• Battery Issues: Replace the CR2032 coin cell if the RTC has lost power or is not maintaining time when the main power supply is disconnected.
• I2C Scanning: Use an I2C scanner sketch to ensure that the Arduino is detecting the RTC module.
• Resetting the Module: If the module is not functioning as expected, a reset can be performed by pulling the RST pin low.

Q: How do I set the time on the DS3231? A: The time can be set using the rtc.adjust(DateTime(...)); function in the Arduino sketch.

Q: Can the DS3231 be used in low-power applications? A: Yes, the DS3231 has a very low power consumption, especially when running off the backup battery.

Q: What is the purpose of the 32K pin? A: The 32K pin outputs a 32kHz square wave that can be used as a clock reference for other devices.