（I/O+IIC+数码管动态显示+键盘扫描+PWM）

1、由数码管低三位L12，L13，L14显示TLC549采集到的电压值X.XX,其他的数码管不亮；

2、电压越高，发光管LED5越亮；电压越低，发光管LED5越暗。-(I/O+IIC+ digital display+ keyboard scan+PWM)

1, by the digital control low voltage X.XX L12,L13,L14 TLC549 collected, other digital tube is not lit

2, the higher the voltage, led LED5 brighter　lower the voltage, led LED5 darker.