1LED灯从高位向低位依次以20000us的时间流水一次，之后完成第2点；
2LED灯从低位向高位依次以25000us 的时间流水两次，之后完成第3点；
3LED灯高四位与低四位以50000us的时间交替闪烁三次，之后完成第4点；
重复执行1~3点。(1LED lights from high to low, in order to 20000us time flow once, and then complete second points;
2LED lights from low to high, in order to 25000us time flow two times, and then complete third points;
3LED lights are four high and four low, alternately flashing three times at 50000us, and then fourth;
Repeat execution of 1~3 points.)