RV-8803-C7 Real-Time Clock Library (ESP32 + Arduino)

An Arduino-compatible library for interfacing with the Micro Crystal RV-8803-C7 I²C real-time clock (RTC), supporting easy epoch-based time read/write.

Key Features

• Simple read/write using Unix Epoch (time_t)
• Compatible with ESP32 and other Arduino-compatible boards
• Uses standard I²C communication via Wire or Wire1
• No internal Wire.begin() — user initializes I²C externally
• Human-readable and epoch-friendly interface

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Basic Usage

RV8803 rtc;

void setup() {

    Serial.begin(19200);

    Wire.begin(48, 47); // SDA, SCL (or use Wire.begin() for default pins)

    rtc.set_epoch(1704067200); // Example: Jan 1, 2024        
}

void loop() {

    time_t now = rtc.get_epoch();
    struct tm *tm = gmtime(&now);

    Serial.printf("%04d-%02d-%02d %02d:%02d:%02d UTC (%ld)\n",
        tm->tm_year + 1900,
        tm->tm_mon + 1,
        tm->tm_mday,
        tm->tm_hour,
        tm->tm_min,
        tm->tm_sec,
        now
    );

    delay(1000);
}

This library simplifies working with the RV-8803 by abstracting I²C register handling into clean epoch-based functions.

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Basic Circuit

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Serial Output

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Documentation & Reference

• RV-8803-C7 Datasheet (PDF)
• CR1225 Coin Cell Specs (PDF)

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I²C Slave Address

The I²C address of the RV-8803 is fixed at 0x32 and cannot be changed.

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Compatibility

This library was tested with:

• ESP32 Arduino Core v3.2.0
  Based on ESP-IDF v5.4.1
  GitHub Release: espressif/arduino-esp32 v3.2.0

For best results, use this or a later version of the Arduino-ESP32 core.