一、独立按键控制LED亮灭

轻触按键：相当于是一种电子开关，按下时开关接通，松开时开关断开，实现原理是通过轻触按键内部的金属弹片受力弹动来实现接通和断开。

#include <STC89C5xRC.H>
void main()
{
//	P2=0xFE;while(1){if(P31==0){P20=0;}else P20=1;}
}

二、独立按键控制LED状态 

对于机械开关，当机械触点断开、闭合时，由于机械触点的弹性作用，一个开关在闭合时不会马上稳定地接通，在断开时也不会一下子断开，所以在开关闭合及断开的瞬间会伴随一连串的抖动。 

#include <STC89C5xRC.H>
void delay(unsigned int x)		//@11.0592MHz
{unsigned char i, j;while(x){i = 2;j = 199;do{while (--j);} while (--i);x--;}
}void main()
{while(1){if(P31==0){delay(20); //Eliminating jitter through delaywhile(P31==0); // 监测松手（松按键）delay(20);P20=~P20;}}
}

三、独立按键控制LED显示二进制

#include <STC89C5xRC.H>
void Delay(unsigned int x)		//@11.0592MHz
{unsigned char i, j;while(x--){i = 2;j = 199;do{while (--j);} while (--i);}
}void main()
{while(1){if(P31==0){Delay(20);while(P31==0);Delay(20);P2--;}}
}

四、独立按键控制LED流水线

#include <STC89C5xRC.H>
void Delay(unsigned int x)		//@11.0592MHz
{unsigned char i, j;while(x--){i = 2;j = 199;do{while (--j);} while (--i);}
}
void main()
{unsigned char pattern=0xFE;while(1){if(P31==0){Delay(20);while(P31==0);Delay(20);P2=pattern;pattern=(pattern<<1)|0x01;if(pattern==0xFF) pattern=0xFE;}}
}

#include <STC89C5xRC.H>
void Delay(unsigned int x)		//@11.0592MHz
{unsigned char i, j;while(x--){i = 2;j = 199;do{while (--j);} while (--i);}
}
void main()
{unsigned char pattern=0xFE;P2=pattern;while(1){if(P31==0){Delay(20);while(P31==0);Delay(20);pattern=(pattern<<1)|0x01;if(pattern==0xFF) pattern=0xFE;P2=pattern;}if(P30==0){Delay(20);while(P30==0);Delay(20);pattern=(pattern>>1)|0x80;if(pattern==0xFF) pattern=0x7F;P2=pattern;}}
}