功能：通过中断接口P3.2连接的独立按键测试，按一次P0口的LED灯反向，

这里使用电平触发，所以一直按键不松开和一次按键效果不相同，一直按下会看到灯全部亮

　　　　说明中断一直在作用，用示波器看则是高频方波-Functions: interrupt interface P3.2 connected independent key test, according to a the P0 port LED lamp reverse, level trigger, and it has been key without releasing a key effect, has been press will see the lights All bright on interrupt has been in the role, with an oscilloscope is a high frequency square wave