通过L297、L298来控制两项步进电机的旋转，速度十档，电机旋转27圈就会回头，再转够27圈自停。可设定好档位后再开始，中途可以自由停止或是换向。-Through L297, L298 to control two stepper motor rotation and speed of ten stalls, motor rotation stop twice. Stalls can be set well after the start, or stop half-way free-for-