读取经X0-X3的数据。
X0 ON ==1 ,X1 ON ==2 , X0 X1 ON ==3 , X2 ON ==4 ,
X0 X2 ON ==5 ,X1 X2 ON ==6 , X0 X1 X2 ON ==7 , X3 ON ==8 ,
X0 X3 ON ==9 ,X1 X3 ON ==10 , X0 X1 X3 ON ==11 , X2 X3 ON ==12 ,
X0 X2 X3ON ==13,X1 X2 X3ON ==14 , X0 X1 X2 X3 ON ==15 , X0 X1 X2 X3 OFF ==0 ,
这样就有16种状态了。