实验板有4个按键，4个LED灯。当按下K1时，流水灯以1秒的速率流动，按下K2时，以5秒的速率流动，按下K3时从向至下流动，按下K4时，从下至上流动。当重复按下按键时，保持功能不变。

-The experimental board has four buttons, four LED lights. Flow from the bottom, press K1, light water flow rate of 1 second, press K2, the rate of flow of 5 seconds, press K3 flow to to press the K4. When the repeat button is pressed to maintain the same functions.