步进电机实验。电机用P1口,键盘使用P3.0、P3.1、P3.2、P3.3。按下K1键，顺时针转，按下K2键，逆时针转，按下K3键，低速，按下K4键，高速。-Stepper motor experiment. Motors P3.0, P3.1, P3.2, P3.3 of P1 port, keyboard. Press K1 key, clockwise, press K2 key, turn counterclockwise, press K3 key, low speed, press