1.用单片机产生的连续可调的PWM波控制直流电机的转速。2.实现四相四拍和四相八拍的切换；速度可以改变；能够实现正转和反转的切换。-1 microcontroller with continuous adjustable PWM wave to control the speed of DC motor. 2 to achieve the four phase four and four phase eight step switching　speed can be changed　switching can realize positive rotation and reverse rotation.