单片机数字钟-LCD1602显示 带四键时钟 按键对应关系： key1 —— 减 key2 —— 加 key3 —— 设定 key4 —— 确定 -Single-chip digital clock-LCD1602 display with four buttons corresponding to the relationship between the clock key: key1- by key2- plus key3- set key4- determine