实现ARM 芯片的一对PWM 输出用于控制直流电机的转动，通过A/D 旋钮控

制其正反转及转速。编程实现ARM 的四路I/O 通道实现环形脉冲分配用于控制步进电机的转动，通过

A/D 旋钮转角控制步进电机的转角。-ARM chip to achieve a PWM control for the DC motor rotation, the A / D control knob and the speed of its reversion. Programming ARM 4P I / O channel to achieve pulse distribution ring used to control the stepping motor rotation, the A / D control knob rotation angle stepper motor.