一 电路

注意：J5跳帽接到2~3引脚，使按键S4-S5四个按键的另外一端接地，从而成为4个独立按键。

二 独立按键工作原理

三 代码

代码1：按下S7点亮L1指示灯，松开按键，指示灯熄灭，按下S6点亮L2指示灯，按下S5点亮L3指示灯，按下S4点亮L4指示灯。

#include "reg52.h"void Delay(unsignde int t)
{while(t--);
}//实现延时功能的函数void InitHC138(unsigned char n)
{switch (n){ case 4;HC138_C = 1;HC138_B = 0;HC138_A = 0;//输出Y4break;case 5;HC138_C = 1;HC138_B = 0;HC138_A = 1;//输出Y5break;
case 4;HC138_C = 1;HC138_B = 1;HC138_A = 0;//输出Y6break;case 5;HC138_C = 1;HC138_B = 1;HC138_A = 1;//输出Y7break;}
}//锁存器选择void dulianjian()
{if(S7 == 0){Delay(100);if(S7 == 0){L1 = 0;while(S7 == 0)L1 = 1;}}if(S6 == 0){Delay(100);if(S6 == 0){L2 = 0;while(S5 == 0)L2 = 1;}}if(S5 == 0){Delay(100);if(S5 == 0){L3 = 0;while(S5 == 0)L3 = 1;}}if(S4 == 0){Delay(100);if(S4 == 0){L4 = 0;while(S4 == 0)L4 = 1;}}
}void main()
{InitHC138(4);while(1){dulianjian();}
}

代码2 ：  S7点亮L1时，S6不可执行操作，S5点亮L3，S4点亮L4；

S6点亮L2时，S7不可执行操作，S5点亮L5，S4点亮L6；

L1，L2均未被点亮时，S5，S4均不可执行操作。

#include "reg52.h"void Delay(unsignde int t)
{while(t--);
}//实现延时功能的函数void InitHC138(unsigned char n)
{switch (n){ case 4;HC138_C = 1;HC138_B = 0;HC138_A = 0;//输出Y4break;case 5;HC138_C = 1;HC138_B = 0;HC138_A = 1;//输出Y5break;
case 4;HC138_C = 1;HC138_B = 1;HC138_A = 0;//输出Y6break;case 5;HC138_C = 1;HC138_B = 1;HC138_A = 1;//输出Y7break;}
}//锁存器选择unsigned char stat_k = 0;
void dulianjian()
{if(S7 == 0){Delay(100);if(stat_k == 0){L1 = 0;stat_k = 1;}else if(stat_k = 1)L1 = 1;stat_k = 0;}}if(S6 == 0){Delay(100);if(stat_k == 0){L2 = 0;stat_k = 2;}else if(stat_k = 2)L2 = 1;stat_k = 0;}}if(S5 == 0){Delay(100);if(stat_k == 1){L3 = 0;while(S5 == 0);L3 = 1;}else if(stat_k = 2)L5 = 0;while(S5 == 0);L5 = 1;}}if(S4 == 0){Delay(100);if(stat_k == 1){L4 = 0;while(S5 == 0);L4 = 1;}else if(stat_k = 2)L6 = 0;while(S5 == 0);L6 = 1;}}
}void main()
{InitHC138(4);while(1){dulianjian();}
}