1. 基本介绍&工作原理

四线编码器：

将旋转位置或旋转量转换成模拟或数字信号的机电设备。其中两根线负责传输电流，另两根同时负责电信号传输，相互配合以起到正反转的效果。特别注意的是，该设备设定一圆周为400pulse，故编程时需要乘以系数360/400=0.9

2. 接线方式

CAN 总线的连接方式是： RoboRIO --> Talon 1 --> Talon 2 --> ... --> PDP
角度传感器的接线方式是：RobotRIO(Analog In) --> Rotation Sensor
按键的接线方式是： `RobotRIO(DIO) --> Digital Push Button

3. 源代码

/*----------------------------------------------------------------------------*/
/* Copyright (c) 2017-2018 FIRST. All Rights Reserved.                        */
/* Open Source Software - may be modified and shared by FRC teams. The code   */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project.                                                               */
/*----------------------------------------------------------------------------*/

package org.usfirst.frc.team5451.robot;

import java.lang.invoke.SwitchPoint;

import com.ctre.phoenix.motorcontrol.*;
import com.ctre.phoenix.motorcontrol.can.TalonSRX;

import edu.wpi.first.wpilibj.GenericHID.Hand;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
import edu.wpi.first.wpilibj.AnalogInput;
import edu.wpi.first.wpilibj.Counter;
import edu.wpi.first.wpilibj.DigitalInput;
import edu.wpi.first.wpilibj.Encoder;
import edu.wpi.first.wpilibj.IterativeRobot;
import edu.wpi.first.wpilibj.Talon;
import edu.wpi.first.wpilibj.XboxController;


public class Robot extends IterativeRobot {
    private XboxController joystick = new XboxController(0); 
    private TalonSRX controller2 = new TalonSRX(10);
    private TalonSRX controller1 = new TalonSRX(11);
    
    private Encoder sampleEncoder = new Encoder(0, 1, false, Encoder.EncodingType.k4X);//定义四线编码器，其中0和1代表robotrio接口，false代表是否反转
    private Counter exampleCounterHi = new Counter(9);//定义三线编码器
    private DigitalInput switch1 = new DigitalInput(2);//定义按键
    private AnalogInput rotational_sensor = new AnalogInput(0);//定义角度传感器
    
    
    
    public static final int kPIDLoopIdx = 0;
    public static final int kTimeoutMs = 30;
        @Override
    public void robotInit() {
        sampleEncoder.setMaxPeriod(.1);
        sampleEncoder.setMinRate(10);
        sampleEncoder.setDistancePerPulse(0.9);//编码器设定一圆周为400单位，0.9=360/400，为系数
        sampleEncoder.setReverseDirection(true);//反转设定
        sampleEncoder.setSamplesToAverage(7);
        sampleEncoder.reset();
        
        exampleCounterHi.setMaxPeriod(.1);
        exampleCounterHi.setUpdateWhenEmpty(true);
        exampleCounterHi.setReverseDirection(false);//反转设定
        exampleCounterHi.setSamplesToAverage(10);
        exampleCounterHi.setDistancePerPulse(3.6);//变慢器设定一圆周为100单位，3.6=360/100，为系数
        
        controller1.configSelectedFeedbackSensor(FeedbackDevice.CTRE_MagEncoder_Absolute, kPIDLoopIdx, kTimeoutMs);
        controller1.setSensorPhase(false);
        controller1.setInverted(true);

        controller1.configNominalOutputForward(0, kTimeoutMs);
        controller1.configNominalOutputReverse(0, kTimeoutMs);
        controller1.configPeakOutputForward(1, kTimeoutMs);
        controller1.configPeakOutputReverse(-1, kTimeoutMs);
        
        controller1.config_kF(kPIDLoopIdx, 0.00, kTimeoutMs);
        controller1.config_kP(kPIDLoopIdx, 0.05, kTimeoutMs);
        controller1.config_kI(kPIDLoopIdx, 0.000295, kTimeoutMs);
        controller1.config_kD(kPIDLoopIdx, 0.003, kTimeoutMs);
    }

    @Override
    public void teleopPeriodic() {
    
        if (joystick.getAButton()) {
            
            sampleEncoder.reset();
        }
        int count = sampleEncoder.get(); 
        double distance = sampleEncoder.getRaw();
        double distance1 = sampleEncoder.getDistance();//得到四线编码器的旋转总角度
        double rate = sampleEncoder.getRate();//得到四线编码器的旋转频率
        boolean direction = sampleEncoder.getDirection();//得到旋转方向
        boolean stopped = sampleEncoder.getStopped();//确定编码器是否停止旋转
        boolean switch2 = switch1.get();//确定按键是否按下
        double rotation = rotational_sensor.getAverageValue()*0.0824;//得到角度传感器的旋转角度
        
        SmartDashboard.putNumber("counter distance", exampleCounterHi.getDistance());
        SmartDashboard.putNumber("counter rate", exampleCounterHi.getRate());
        SmartDashboard.putNumber("distance", distance1);
        SmartDashboard.putBoolean("direction", direction);
        SmartDashboard.putBoolean("stopped", stopped);
        SmartDashboard.putNumber("rate", rate);
        SmartDashboard.putBoolean("switch", switch2);
        SmartDashboard.putNumber("rotation", rotation);
                //将数值显示在dashboard上
    }
}