The DS1308 is a low-power, full binary-coded decimal serial real-time clock (RTC). The clock provides seconds, minutes, hours, day, date, month and year informations. It operates in either the 24-hour or 12-hour format with AM/PM indicator. It also has a built-in power-sense circuit which detects power failures and switches to the backup supply, here a coin cell, to maintain time and date operation.
- Low timekeeping current of 250 nA, which allows to it run on the coin cell for more than 20 years
- Automatically switches to the backup battery when a powerful failure is detected
- Simple I2C interface
Adafruit have developed a library available on their GitHub repo.
This function includes a coin cell holder on the PCB, where you can insert a CR1220 or CR1225 backup battery.