按上/下键修改LED数码管显示数值，输出D/A转换后的电压值，方案2-up and down key to change the dispay number and output a D/A voltage

此代码可以实现对三极管的计数，其采用的软件是matlab.但是前提下是数码管不要重叠-This code can be achieved on the transistor count, which uses the software matlab., But the premise is not overlapping digital! !