This Arduino library provides an interface for the DS1307 Real Time Clock (RTC) module. It supports both hardware I2C communication with the DS1307 and a software-based RTC (softRTC_lite) for maintaining time between hardware updates.

• Time Setting: Easily set the RTC time.
• 12‑Hour and 24‑Hour Formats: Retrieve and print time in both formats.
• Weekday Support: Calculate and display weekdays (e.g., Sun, Mon, Tue, etc.).
• Square Wave Output: Configure the DS1307 to output a 1Hz (or selectable frequencies) square wave on the SW pin.
• NVRAM Access: Read from and write to the DS1307 onboard RAM (56 bytes).

Instantiate the tinyRTCds1307 class, initialize the I2C communication, and set the RTC time. For example:

#define RTC_FEATURE_WEEKDAYS 1
#define RTC_FEATURE_12H_TIME 1
#define RTC_FEATURE_SERIAL_PRINT 1

#include <Wire.h>
#include <tinyRTCds1307.h>

tinyRTCds1307 rtc;

void setup() {
  Serial.begin(9600);
  Wire.begin();
  // Set RTC time: day, month, year, hour, minute, second.
  rtc.setTime(21, 3, 2025, 21, 30, 0);
  rtc.sync(); // Sync time between software and hardware rtc.
  Serial.println("RTC time set to 21-03-2025 09:30:00 PM");
}

void loop() {
  // Print current time in 12-hour format with weekday
  rtc.printTime();
  delay(1000);
}

Configure the RTC to output a 1Hz square wave on its SW pin and display time in 24‑hour format with weekday support:

#define RTC_FEATURE_BLINK 1
#define RTC_FEATURE_WEEKDAYS 1
#define RTC_FEATURE_12H_TIME 0
#define RTC_FEATURE_SERIAL_PRINT 1

#include <Wire.h>
#include <tinyRTCds1307.h>

tinyRTCds1307 rtc;

void setup() {
  Serial.begin(9600);
  Wire.begin();
  // Optionally set the RTC time here
  // rtc.setTime(21, 3, 2025, 21, 30, 0);
  rtc.sync(); //synchronize time
  // Enable 1Hz square wave on the SW pin.
  rtc.setOscillator(true, rtc_osc_1hz);
  Serial.println("RTC 1Hz square wave enabled on SW pin");
}

void loop() {
  rtc.printTime();
  delay(1000);
}

Write to and read from the DS1307's onboard NVRAM:

#define RTC_FEATURE_RAM 1
#define RTC_FEATURE_SERIAL_PRINT 1

#include <Wire.h>
#include <tinyRTCds1307.h>

tinyRTCds1307 rtc;

void setup() {
  Serial.begin(9600);
  Wire.begin();
  
  // Write a byte (0x55) to NVRAM address 0.
  rtc.writeRam(0, 0x55);
  Serial.print("Written to NVRAM address 0: 0x");
  Serial.println(0x55, HEX);
  
  // Read the byte back.
  uint8_t data = rtc.readRam(0);
  Serial.print("Read from NVRAM address 0: 0x");
  Serial.println(data, HEX);
}

void loop() {
  // No repeated action needed.
}

The library supports several preprocessor directives to enable or disable specific features. Define these before including the library header:

• RTC_FEATURE_WEEKDAYS – Enable weekday functionality.
• RTC_FEATURE_12H_TIME – Enable 12‑hour time format.
• RTC_FEATURE_SERIAL_PRINT – Enable serial time printing.
• RTC_FEATURE_RAM – Enable NVRAM (RAM) read/write functions.
• RTC_FEATURE_BLINK – Enable square wave output functionality.

You can install this library using the Arduino Library Manager by searching for "DS1307" or by cloning the repository:

git clone https://github.com/manzarehassin/tinyRTCds1307.git

• Architectures: AVR, ESP8266, MegaAVR (see library.properties for complete details)
• Dependencies: Arduino core, Wire library.

This library is distributed under the MIT License. See the LICENSE file for details.

For the latest updates and more detailed documentation, visit the DS1307RTC GitHub Repository.

Published on: 21 March, 2025 9:30 PM (UTC+6)
Author: Manzar E Hassin mnz247@hotmail.com