求大神帮我看看为啥调节滑阻，电压值不变呢

正文摘要:

#include<reg52.h> #include<intrins.h> #include"LCD.h" sbit AD_EOC=P3^0; sbit AD_START=P3^3; sbit AD_OE=P3^4; sbit s1=P2^3; sbit s2=P2^4; sbit s3=P2^5; #define _300v_on {s1=1;s2=0;s3= ...