### **Project 35: DS3231 Clock Module**

**1. Introduction**
DS3231 is equipped with integrated TCXO and crystal, which make it a cost-effective I2C real time clock with high precision. 

The device carries a battery input, so if you disconnect the main power supply, it can still maintain accurate timing. The integrated oscillator ensures the long-term accuracy of the device and reduces the number of components.

DS3231 provides both commercial and industrial temperature range and supports 16 pins small-outline package (300mil). The module itself can adapt to the system of 3.3V and 5V without level switch, which is quite convenient!

![](media/image-20251121134450627.png)

**2. Specification**

- Temperature range: -40 to +85; Timing accuracy: ± 5ppm (±0.432 seconds/day)
- Provide battery backup for continuous timing
- Low power consumption
- Device package and function compatible with DS3231
- Complete clock calendar function contains seconds and minutes, hour, week, date, month, and year timing and provides leap year compensation until 2100.
- Two calendar clock
- Output: 1Hz and 32.768kHz
- Reset output and Input Debounce of Pushbutton
- High speed (400kHz), I2C serial bus
- Supply voltage: +3.3V to +5.5V
- Digital temperature sensor with a precision of±3℃
- Working temperature: -40 ~ C to +85 ~ C
- 16 pins Small Outline Package (300mil)

**3. Connection Diagram**
This module adopts the IIC test method, so we only need to connect SDA to Arduino A4; SCL to A5; positive pin to VCC; negative pin to GND.

![](media/image-20251121134557081.png)

**4. Sample Code**

```c
#include <Wire.h>
#include "DS3231.h"
DS3231 RTC; //Create the DS3231 object
char weekDay[][4] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
//year, month, date, hour, min, sec and week-day(starts from 0 and goes to 6)
//writing any non-existent time-data may interfere with normal operation of the RTC.
//Take care of week-day also.
DateTime dt(2011, 11, 10, 15, 18, 0, 5);//open the serial port and you can check time here or make a change to the time as needed.

void setup () 
{   Serial.begin(57600);//set baud rate to 57600
    Wire.begin();
    RTC.begin();
    RTC.adjust(dt); //Adjust date-time as defined 'dt' above 
}

void loop () 
{  
 DateTime now = RTC.now(); //get the current date-time
    Serial.print(now.year(), DEC);
    Serial.print('/');
    Serial.print(now.month(), DEC);
    Serial.print('/');
    Serial.print(now.date(), DEC);

    Serial.print(' ');
    Serial.print(now.hour(), DEC);
    Serial.print(':');
    Serial.print(now.minute(), DEC);
    Serial.print(':');
    Serial.print(now.second(), DEC);
    Serial.println();
    Serial.print(weekDay[now.dayOfWeek()]);
    Serial.println();
    delay(1000);
}
```

When the above steps are done, you can upload the code to arduino and open the serial monitor and get the following results:

![](media/12.png)