树莓派UNL2003是如何驱动28BYJ-48步进电机

import com.pi4j.io.gpio.GpioController;import com.pi4j.io.gpio.GpioFactory;import com.pi4j.io.gpio.GpioPinDigitalOutput;import com.pi4j.io.gpio.PinState;import com.pi4j.io.gpio.RaspiPin;import java.util.Scanner;public class test{   //获取全局Gpio 引脚.