步进电机的驱动子程序，可应用在电脑磁盘读写电机的驱动，嵌入式爱好者可以学习一下了。内含正反转，精确定位子函数。-Stepper motor drive subroutine, read and write can be used in computer disk drive motor, embedded lovers can learn about the whole thing. Includes reversing, accurate positioning subroutine.