12864液晶在出厂时其对比度已经调好，所以用户在使用的时候第三管脚可不用接任何东西，本实验板上为了兼容多家12864液晶所以加了液晶对比度调节电位器，若用户使用我们配套的12864液晶可不用管它，液晶的第三管脚悬空就可以。有些液晶功耗比较大，用户在使用的时候可将液晶的第19、20引脚的背光不接，这样字体会很清楚。-12864 at the factory the contrast has been tuned to the user when in use the third pin can not pick anything, this experiment board so the addition to compatible with more than 12,864 LCD LCD contrast adjustment potentiometer, if the usersupporting the 12864 do not cares, the third pin of the LCD is vacant you can. Some LCD power consumption is relatively large, when in use the backlight of the LCD 19, 20 pins not then, so the font will be very clear.