How to Use DS 3231 RTC: Examples, Pinouts, and Specs

The DS3231 RTC module, manufactured by DORHEA (Part ID: DS3231 AT24C32), is a highly accurate real-time clock (RTC) designed to keep track of time and date. It features a temperature-compensated crystal oscillator (TCXO) to ensure precise timekeeping, even under varying environmental conditions. The module communicates via the I2C interface, making it easy to integrate with microcontrollers like Arduino, Raspberry Pi, and other embedded systems.

• Time-stamping data in data logging systems
• Alarm clock and timer applications
• Scheduling tasks in embedded systems
• Real-time event tracking in IoT devices
• Calendar-based automation systems

The DS3231 RTC module is designed for high accuracy and ease of use. Below are its key technical details:

• Operating Voltage: 3.3V to 5.5V
• Timekeeping Accuracy: ±2 ppm (parts per million) from 0°C to +40°C
• Interface: I2C (2-wire)
• Temperature Range: -40°C to +85°C
• Backup Battery Support: CR2032 coin cell battery
• Memory: Includes an AT24C32 EEPROM (32KB) for additional data storage
• Oscillator: Built-in temperature-compensated crystal oscillator (TCXO)
• Alarm Functions: Two programmable alarms
• Square Wave Output: Configurable frequency (1Hz, 4kHz, 8kHz, 32kHz)

The DS3231 RTC module has the following pinout:

The DS3231 RTC module is straightforward to use in a circuit. Below are the steps and best practices for integrating it into your project.

1. Power the Module: Connect the VCC pin to a 3.3V or 5V power source and the GND pin to ground.
2. Connect I2C Lines:
   • Connect the SDA pin to the SDA pin of your microcontroller.
   • Connect the SCL pin to the SCL pin of your microcontroller.
3. Optional Connections:
   • Use the SQW/OUT pin for square wave output or alarms if needed.
   • The 32K pin can be used for an external 32kHz clock signal.
4. Install Backup Battery: Insert a CR2032 coin cell battery into the battery holder to maintain timekeeping during power loss.

• Pull-Up Resistors: Ensure that the I2C lines (SDA and SCL) have pull-up resistors (typically 4.7kΩ). Some modules include these resistors by default.
• Battery Backup: Always use a backup battery to maintain timekeeping when the main power supply is disconnected.
• EEPROM Usage: The onboard AT24C32 EEPROM can be used to store additional data, such as configuration settings or logs.
• Temperature Compensation: The DS3231 automatically adjusts for temperature variations, so no manual calibration is required.

Below is an example of how to use the DS3231 RTC module with an Arduino UNO. This code sets the time and reads the current time and date.

#include <Wire.h>
#include <RTClib.h> // Include the Adafruit RTC library

RTC_DS3231 rtc; // Create an RTC object

void setup() {
  Serial.begin(9600); // Initialize serial communication
  Wire.begin();       // Initialize I2C communication

  if (!rtc.begin()) {
    Serial.println("Couldn't find RTC module!");
    while (1); // Halt execution if RTC is not found
  }

  if (rtc.lostPower()) {
    Serial.println("RTC lost power, setting the time!");
    // Set the RTC to the current date and time
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }
}

void loop() {
  DateTime now = rtc.now(); // Get the current time and date

  // Print the current time and date to the Serial Monitor
  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); // Wait for 1 second before updating
}

1. RTC Not Detected by Microcontroller:

   • Ensure the SDA and SCL lines are correctly connected.
   • Check if pull-up resistors are present on the I2C lines.
   • Verify the I2C address of the module (default is 0x68).

2. Incorrect Time or Date:

   • If the RTC lost power, reinitialize the time using the rtc.adjust() function.
   • Ensure the backup battery is installed and functional.

3. Square Wave Output Not Working:

   • Verify that the SQW/OUT pin is configured correctly in the software.
   • Check the module's datasheet for square wave configuration commands.

4. EEPROM Not Accessible:

   • Ensure the EEPROM I2C address (0x57) is used when accessing the AT24C32 memory.

• Q: Can the DS3231 RTC module work without a backup battery?
  A: Yes, but it will lose timekeeping functionality when the main power is disconnected.

• Q: What is the default I2C address of the DS3231?
  A: The default I2C address is 0x68.

• Q: How accurate is the DS3231 RTC module?
  A: The module has an accuracy of ±2 ppm from 0°C to +40°C, which translates to a drift of about ±1 minute per year.

• Q: Can I use the DS3231 with a 3.3V microcontroller?
  A: Yes, the module supports both 3.3V and 5V logic levels.

By following this documentation, you can effectively integrate and use the DS3231 RTC module in your projects.