001// Copyright (c) FIRST and other WPILib contributors.
002// Open Source Software; you can modify and/or share it under the terms of
003// the WPILib BSD license file in the root directory of this project.
004
005package edu.wpi.first.wpilibj;
006
007import edu.wpi.first.util.sendable.Sendable;
008import edu.wpi.first.util.sendable.SendableBuilder;
009import edu.wpi.first.util.sendable.SendableRegistry;
010
011/**
012 * Class for reading analog potentiometers. Analog potentiometers read in an analog voltage that
013 * corresponds to a position. The position is in whichever units you choose, by way of the scaling
014 * and offset constants passed to the constructor.
015 */
016public class AnalogPotentiometer implements Sendable, AutoCloseable {
017  private AnalogInput m_analogInput;
018  private boolean m_initAnalogInput;
019  private double m_fullRange;
020  private double m_offset;
021
022  /**
023   * AnalogPotentiometer constructor.
024   *
025   * <p>Use the fullRange and offset values so that the output produces meaningful values. I.E: you
026   * have a 270 degree potentiometer, and you want the output to be degrees with the halfway point
027   * as 0 degrees. The fullRange value is 270.0(degrees) and the offset is -135.0 since the halfway
028   * point after scaling is 135 degrees. This will calculate the result from the fullRange times the
029   * fraction of the supply voltage, plus the offset.
030   *
031   * @param channel The analog input channel this potentiometer is plugged into. 0-3 are on-board
032   *     and 4-7 are on the MXP port.
033   * @param fullRange The scaling to multiply the fraction by to get a meaningful unit.
034   * @param offset The offset to add to the scaled value for controlling the zero value
035   */
036  public AnalogPotentiometer(final int channel, double fullRange, double offset) {
037    this(new AnalogInput(channel), fullRange, offset);
038    m_initAnalogInput = true;
039    SendableRegistry.addChild(this, m_analogInput);
040  }
041
042  /**
043   * AnalogPotentiometer constructor.
044   *
045   * <p>Use the fullRange and offset values so that the output produces meaningful values. I.E: you
046   * have a 270 degree potentiometer, and you want the output to be degrees with the halfway point
047   * as 0 degrees. The fullRange value is 270.0(degrees) and the offset is -135.0 since the halfway
048   * point after scaling is 135 degrees. This will calculate the result from the fullRange times the
049   * fraction of the supply voltage, plus the offset.
050   *
051   * @param input The {@link AnalogInput} this potentiometer is plugged into.
052   * @param fullRange The angular value (in desired units) representing the full 0-5V range of the
053   *     input.
054   * @param offset The angular value (in desired units) representing the angular output at 0V.
055   */
056  public AnalogPotentiometer(final AnalogInput input, double fullRange, double offset) {
057    SendableRegistry.addLW(this, "AnalogPotentiometer", input.getChannel());
058    m_analogInput = input;
059    m_initAnalogInput = false;
060
061    m_fullRange = fullRange;
062    m_offset = offset;
063  }
064
065  /**
066   * AnalogPotentiometer constructor.
067   *
068   * <p>Use the scale value so that the output produces meaningful values. I.E: you have a 270
069   * degree potentiometer, and you want the output to be degrees with the starting point as 0
070   * degrees. The scale value is 270.0(degrees).
071   *
072   * @param channel The analog input channel this potentiometer is plugged into. 0-3 are on-board
073   *     and 4-7 are on the MXP port.
074   * @param scale The scaling to multiply the voltage by to get a meaningful unit.
075   */
076  public AnalogPotentiometer(final int channel, double scale) {
077    this(channel, scale, 0);
078  }
079
080  /**
081   * AnalogPotentiometer constructor.
082   *
083   * <p>Use the fullRange and offset values so that the output produces meaningful values. I.E: you
084   * have a 270 degree potentiometer, and you want the output to be degrees with the starting point
085   * as 0 degrees. The scale value is 270.0(degrees).
086   *
087   * @param input The {@link AnalogInput} this potentiometer is plugged into.
088   * @param scale The scaling to multiply the voltage by to get a meaningful unit.
089   */
090  public AnalogPotentiometer(final AnalogInput input, double scale) {
091    this(input, scale, 0);
092  }
093
094  /**
095   * AnalogPotentiometer constructor.
096   *
097   * <p>The potentiometer will return a value between 0 and 1.0.
098   *
099   * @param channel The analog input channel this potentiometer is plugged into. 0-3 are on-board
100   *     and 4-7 are on the MXP port.
101   */
102  public AnalogPotentiometer(final int channel) {
103    this(channel, 1, 0);
104  }
105
106  /**
107   * AnalogPotentiometer constructor.
108   *
109   * <p>The potentiometer will return a value between 0 and 1.0.
110   *
111   * @param input The {@link AnalogInput} this potentiometer is plugged into.
112   */
113  public AnalogPotentiometer(final AnalogInput input) {
114    this(input, 1, 0);
115  }
116
117  /**
118   * Get the current reading of the potentiometer.
119   *
120   * @return The current position of the potentiometer.
121   */
122  public double get() {
123    if (m_analogInput == null) {
124      return m_offset;
125    }
126    return (m_analogInput.getAverageVoltage() / RobotController.getVoltage5V()) * m_fullRange
127        + m_offset;
128  }
129
130  @Override
131  public void initSendable(SendableBuilder builder) {
132    if (m_analogInput != null) {
133      builder.setSmartDashboardType("Analog Input");
134      builder.addDoubleProperty("Value", this::get, null);
135    }
136  }
137
138  @Override
139  public void close() {
140    SendableRegistry.remove(this);
141    if (m_initAnalogInput) {
142      m_analogInput.close();
143      m_analogInput = null;
144      m_initAnalogInput = false;
145    }
146  }
147}