Standalone minimal RTC helper for DS1307/DS3231 over I2C. No RTClib dependency, no dynamic allocation, and no String usage. Provides only the essentials: init, running check, compile-time fallback set, explicit set, read, and signed adjustments. Maintained by pandiyarajk.

Files

• library.properties — Arduino library metadata.
• src/RTCManager.h/.cpp — lightweight RTC class.
• keywords.txt — Arduino IDE highlighting.
• examples/Basic/Basic.ino — minimal usage.
• LICENSE — MIT.

API (RTCManager)

• bool begin() — init RTC, returns false if not found.
• bool isRunning() — true if oscillator runs (checks CH bit).
• RTCStatus status() const — last status code.
• bool setCompileTimeIfStopped() — set to compile time if stopped.
• bool setTime(const SimpleDateTime& dt) — write explicit time.
• bool adjustMinutes(int16_t delta) — add/sub minutes (saturates at 2000-01-01).
• bool adjustSeconds(int32_t delta) — add/sub seconds (saturates at 2000-01-01).
• bool readNow(SimpleDateTime& out) — get current time.

Usage

#include <RTCManager.h>

RTCManager rtcMgr;

void setup() {
  Serial.begin(9600);
  if (!rtcMgr.begin()) {
    Serial.println(F("RTC not found"));
    while (1);
  }
  rtcMgr.setCompileTimeIfStopped(); // optional first-time set
}

void loop() {
  SimpleDateTime now;
  if (rtcMgr.readNow(now)) {
    Serial.print(now.hour); Serial.print(':');
    Serial.print(now.minute); Serial.print(':');
    Serial.println(now.second);
  }
  delay(1000);
}

Adjust time examples

rtcMgr.adjustMinutes(3);    // add 3 minutes
rtcMgr.adjustMinutes(-5);   // subtract 5 minutes
rtcMgr.adjustSeconds(90);   // add 90 seconds
rtcMgr.setTime(SimpleDateTime{2025, 12, 8, 17, 41, 0}); // explicit set

Status codes

• RTC_STATUS_OK
• RTC_STATUS_NOT_FOUND
• RTC_STATUS_NOT_RUNNING
• RTC_STATUS_SET_COMPILE_TIME

Notes

• Uses Wire only; keep coin-cell fresh for persistence.
• DS3231 offers better accuracy than DS1307; both share the same register layout for basic time-keeping.

Installing (local ZIP)

• Zip the rtc_lib folder (ensure library.properties is at root of zip).
• Arduino IDE: Sketch → Include Library → Add .ZIP Library.