How to Use DS1307 RTC (Wokwi Compatible): Examples, Pinouts, and Specs

The DS1307 RTC (Real-Time Clock) is a low-power, full binary-coded decimal (BCD) clock/calendar with 56 bytes of NV SRAM. It communicates with a microcontroller via the I2C protocol and is used to keep track of time even when the main device is powered off. The Wokwi Compatible version is designed for easy integration with the Wokwi simulation platform.

• Time-stamping data logs
• Real-time clocks for embedded systems
• Alarm clocks
• Timers and counters
• Time-based automation systems

1. Power Supply: Connect the VCC pin to a 5V power supply and the GND pin to ground.
2. I2C Communication: Connect the SCL pin to the I2C clock line of your microcontroller and the SDA pin to the I2C data line.
3. Battery Backup: Connect a 3V lithium cell to the VBAT pin to maintain timekeeping when the main power is off.
4. Optional Output: The SQW/OUT pin can be used to output a square wave or as a general-purpose output.

• Pull-up Resistors: Ensure that the I2C lines (SCL and SDA) have pull-up resistors (typically 4.7kΩ) to the VCC.
• Battery Backup: Use a suitable 3V lithium cell for the VBAT pin to ensure continuous timekeeping.
• Decoupling Capacitor: Place a 0.1µF decoupling capacitor close to the VCC pin to filter out noise.

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

RTC_DS1307 rtc;

void setup() {
  Serial.begin(9600);
  Wire.begin();
  rtc.begin();

  if (!rtc.isrunning()) {
    Serial.println("RTC is NOT running!");
    // Set 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);
}

1. RTC Not Keeping Time: Ensure the battery is properly connected to the VBAT pin.
2. I2C Communication Failure: Check the connections and ensure pull-up resistors are in place.
3. Incorrect Time: Verify that the RTC is initialized and set correctly.

• Check Connections: Ensure all connections are secure and correct.
• Verify Power Supply: Make sure the VCC pin is receiving a stable 5V supply.
• Use Pull-up Resistors: Ensure that the I2C lines have appropriate pull-up resistors.
• Initialize RTC: If the RTC is not running, initialize it using the rtc.adjust() function.

By following this documentation, users should be able to effectively integrate and utilize the DS1307 RTC in their projects, ensuring accurate timekeeping and reliable performance.