此程序是用51单片机开发的，步进电机正反转及调速控制的程序。-This program is the development of 51 single-chip stepper motor speed control and reversing the procedure.

stm32平台，输出4路PWM解锁电调，pwm输出频率为50HZ，调整占空比达到控制电机转速目的(STM32 platform, output 4 PWM unlock electric adjustment)