RTC2 Click is an accessory board in mikroBus™ form factor. It features the DS1307 serial real-time clock (RTC). It is a low-power, full binary-coded decimal (BCD) clock/calendar with programmable square-wave output signal. Board uses I2C interface for communication, and can only use 5V power supply. Board features a 3V/230mA lithium battery as a backup power supply which ensures that timekeeping operation continues even when the main power supply goes OFF.