无线键盘的四个译码输出口从低到高依次对应于P1口的低四位 下面是无线键盘的键值分布 8 4 2 1 码输出； 返回的直接就是键值 （很好用）-Wireless keyboard four decoding output from low to high in turn corresponds to the P1 population is below the low of four key distribution of wireless keyboard 8 4 2 1 Code