This a custom designed module for the DS1307 Real Time Clock. The module comes fully assembled and pre-programmed with the current time (ok, so it’s * our current time – *MST). The DS1307 RTC is accessed via the I2C protocol. We’ve written a test-bed to program the modules. This test-bed code should give you some insight on how to interface the module to any microcontroller using our example software I2C and BCD routines.
Features:
- Two wire I2C interface
- Hour : Minutes : Seconds AM/PM
- Day Month, Date – Year
- Leap year compensation
- Accurate calendar up to year 2100
- Battery Not included
- 1Hz output pin
- 56 Bytes of Non-volatile memory available to user
Wiring the RTC to Arduino

Arduino Tiny RTC I2C Real Time Clock Pinout | ||
| PIN | Description | Comment |
| BAT | Battery voltage | To monitor the battery voltage, or not connected |
| GND | Ground | Ground |
| VCC | 5V supply | Power the module and charge the battery |
| SDA | I2C data | I2C data for the RTC |
| SCL | I2C clock | I2C clock for the RTC |
| DS | DS18B20 Temp. Sensor output | One wire inteface |
| SQ | Square wave output | Normally not used |
The I2C wires “SDA” and “SCL” are the data line and clock line, they should be connected to the corresponding pins depending on the Arduino board.
| Board | I2C / TWI pins |
| Uno, Ethernet | A4 (SDA), A5 (SCL) |
| Mega2560 | 20 (SDA), 21 (SCL) |
| Leonardo | 2 (SDA), 3 (SCL) |
| Due | 20 (SDA), 21 (SCL), SDA1, SCL1 |
Example code is available here.
Documents:
Software:
- Example 16F88 code
- Arduino Tutorial. Thanks John Vaughters!
- Arduino Tutorial in Portuguese. Thanks Daniel Gonçalves!
- Bildr Tutorial














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