说明：  目前比较流行的一种通信协议------I2C总线协议（AT2402），里面包含此协议的通信规则，驱动lcd1602显示时钟，并且在断电后依然保存数据,省去再调烦恼。
(A current popular communication protocols------ I2C bus protocol (AT2402), which contains the rules of this agreement, communication, drive lcd1602 show the clock, and save data even after power failure, eliminating the need to stress the trouble.)