Fixes bugs with the Gyro

If the gyro was initialized with an analog input the gyro class would not be calibrated properly.
Removes unnecessary type casting.

Change-Id: I6baa72919019a33cce7d3074f8477104cbe65396

wpilibj/wpilibJavaDevices/src/main/java/edu/wpi/first/wpilibj/Gyro.java

@@ -8,7 +8,6 @@ package edu.wpi.first.wpilibj;
 
 import edu.wpi.first.wpilibj.communication.FRCNetworkCommunicationsLibrary.tResourceType;
 import edu.wpi.first.wpilibj.communication.UsageReporting;
-import edu.wpi.first.wpilibj.Timer;
 import edu.wpi.first.wpilibj.livewindow.LiveWindow;
 import edu.wpi.first.wpilibj.livewindow.LiveWindowSendable;
 import edu.wpi.first.wpilibj.tables.ITable;
@@ -30,11 +29,11 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	static final double kSamplesPerSecond = 50.0;
 	static final double kCalibrationSampleTime = 5.0;
 	static final double kDefaultVoltsPerDegreePerSecond = 0.007;
-	AnalogInput m_analog;
+	private AnalogInput m_analog;
 	double m_voltsPerDegreePerSecond;
 	double m_offset;
 	int m_center;
-	boolean m_channelAllocated;
+	boolean m_channelAllocated = false;
 	AccumulatorResult result;
 	private PIDSourceParameter m_pidSource;
 
@@ -60,6 +59,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 
 		Timer.delay(1.0);
 		m_analog.initAccumulator();
+		m_analog.resetAccumulator();
 
 		Timer.delay(kCalibrationSampleTime);
 
@@ -68,7 +68,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 		m_center = (int) ((double) result.value / (double) result.count + .5);
 
 		m_offset = ((double) result.value / (double) result.count)
-				- (double) m_center;
+				- m_center;
 
 		m_analog.setAccumulatorCenter(m_center);
 
@@ -89,15 +89,13 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	 *            The analog channel the gyro is connected to.
 	 */
 	public Gyro(int channel) {
-		m_analog = new AnalogInput(channel);
+		this(new AnalogInput(channel));
 		m_channelAllocated = true;
-		initGyro();
 	}
 
 	/**
 	 * Gyro constructor with a precreated analog channel object. Use this
-	 * constructor when the analog channel needs to be shared. There is no
-	 * reference counting when an AnalogChannel is passed to the gyro.
+	 * constructor when the analog channel needs to be shared.
 	 *
 	 * @param channel
 	 *            The AnalogChannel object that the gyro is connected to.
@@ -105,12 +103,9 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	public Gyro(AnalogInput channel) {
 		m_analog = channel;
 		if (m_analog == null) {
-			System.err
-					.println("Analog channel supplied to Gyro constructor is null");
-		} else {
-			m_channelAllocated = false;
-			initGyro();
+			throw new NullPointerException("AnalogInput supplied to Gyro constructor is null");
 		}
+		initGyro();
 	}
 
 	/**
@@ -128,6 +123,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	 * Delete (free) the accumulator and the analog components used for the
 	 * gyro.
 	 */
+	@Override
 	public void free() {
 		if (m_analog != null && m_channelAllocated) {
 			m_analog.free();
@@ -176,7 +172,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 		if (m_analog == null) {
 			return 0.0;
 		} else {
-			return (m_analog.getAverageValue() - ((double) m_center + m_offset))
+			return (m_analog.getAverageValue() - (m_center + m_offset))
 					* 1e-9
 					* m_analog.getLSBWeight()
 					/ ((1 << m_analog.getOversampleBits()) * m_voltsPerDegreePerSecond);
@@ -213,6 +209,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	 *
 	 * @return the current angle according to the gyro
 	 */
+	@Override
 	public double pidGet() {
 		switch (m_pidSource.value) {
 		case PIDSourceParameter.kRate_val:
@@ -227,6 +224,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	/*
 	 * Live Window code, only does anything if live window is activated.
 	 */
+	@Override
 	public String getSmartDashboardType() {
 		return "Gyro";
 	}
@@ -236,6 +234,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	/**
 	 * {@inheritDoc}
 	 */
+	@Override
 	public void initTable(ITable subtable) {
 		m_table = subtable;
 		updateTable();
@@ -244,6 +243,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	/**
 	 * {@inheritDoc}
 	 */
+	@Override
 	public ITable getTable() {
 		return m_table;
 	}
@@ -251,6 +251,7 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	/**
 	 * {@inheritDoc}
 	 */
+	@Override
 	public void updateTable() {
 		if (m_table != null) {
 			m_table.putNumber("Value", getAngle());
@@ -260,12 +261,14 @@ public class Gyro extends SensorBase implements PIDSource, LiveWindowSendable {
 	/**
 	 * {@inheritDoc}
 	 */
+	@Override
 	public void startLiveWindowMode() {
 	}
 
 	/**
 	 * {@inheritDoc}
 	 */
+	@Override
 	public void stopLiveWindowMode() {
 	}
 }