说明：  本程序用于测试4相步进电机常规驱动 4个按键分别控制加速、减速、开启、停止.数码管显示 01-18速度等级，数字越大，速度越大
(This procedure is used to test the conventional 4-phase stepper motor driven four buttons control the acceleration, deceleration, start, stop. 01-18 digital display speed rating, the higher the number, the greater the speed)