1602显示直流电机调速，按键控制速度增加(1602 display DC motor speed, key control speed increases)

直流电机调速：stc单片机产生0-99%可调的PWM信号。用1602显示PWM信号的占空比。和电机的转速。(DC motor speed: stc microcontroller 0-99% adjustable PWM signal. Use 1602 to display the duty cycle of the PWM signal. And the speed of the motor.)