//串行驱动led显示， //一个74hc595位移寄存器驱动三极管驱动led位， //两个74hc595驱动led段，方式位5位x8段x2=10个数码管 //5分频，每次扫描时间位1.25ms //定义特殊符号-/ / Serial Driver led, / / a 74hc595 displacement register drives the triode-led drive, / / 2 74hc595 led drive, five-way x8 of x2 = 10 digital