使用51单片机控制L293D电机驱动板，控制智能小车的四个轮子，实现前进倒退转向，51单片机作为下位机预留几个io口供上位机操作(The use of 51 single-chip microcomputer control L293D motor driver board, control the four wheels of the smart car, to achieve forward backward turn, 51 SCM as a lower computer, set asi