By setting the duty cycle of the PWM wave to control the speed of the DC motor, the larger the duty cycle, the faster the speed, the smaller the speed. 2, of course, the I\/O port of the MCU can not directly drive the motor, so you also need to use a motor to drive the chip. Like LG9110, CMO825, etc. The motor drive IC can amplify the microcontroller I\/O output signal, so that the current flowing through the motor is large enough to turn the motor. 3, if you do not clear the PWM is what is going on, you can first do some understanding, and then know that there are signs to ask questions.