The module is based on DS1307 high precision real time clock module; Through I2C interface to communicate with singlechip can read year month day week time minute second; Car read until 2100 year; Control interface is I2C; Recommended power: DC 5V; The address of the module is 0x68; Control interface level is 5V or 3.3V; 4-M2 screw hole easy to install. Specification Power voltage VCC: 4.5~5.5V; Battery voltage: 2.0~3.5V; High level input: 2.1~VCC + 0.3V; Low level input: -0.3~+0.8V; Control interface: 4-pin (GND VCC SDA SCL) GND for ground wire VCC for power source SDA for I2C interface data cable SCL for I2C interface clock cable; Real time IC: DS1307Z; Independent timing: through I2C interface communicate with MCU; Battery: CR1220; Installed hole: 4-M2 screw hole diameter hole: 2.2mm easy to install