[hal,wpilib] Rename FPGA clock to monotonic clock (#8672)

- Remove status return from HAL level (clock getting should never fail)
- Remove 32-bit timestamp expand function
- Make monotonic_clock.hpp (formerly fpga_clock.hpp) header-only and
move to root hal include directory

wpilibj/src/main/java/org/wpilib/framework/TimedRobot.java

@@ -44,7 +44,7 @@ public class TimedRobot extends IterativeRobotBase {
           startTime
               + offset
               + this.period
-              + (RobotController.getFPGATime() - startTime) / this.period * this.period;
+              + (RobotController.getMonotonicTime() - startTime) / this.period * this.period;
     }
 
     @Override
@@ -89,7 +89,7 @@ public class TimedRobot extends IterativeRobotBase {
    */
   protected TimedRobot(double period) {
     super(period);
-    m_startTimeUs = RobotController.getFPGATime();
+    m_startTimeUs = RobotController.getMonotonicTime();
     addPeriodic(this::loopFunc, period);
     NotifierJNI.setNotifierName(m_notifier, "TimedRobot");
 
@@ -146,7 +146,7 @@ public class TimedRobot extends IterativeRobotBase {
         break;
       }
 
-      long currentTime = RobotController.getFPGATime();
+      long currentTime = RobotController.getMonotonicTime();
       m_loopStartTimeUs = currentTime;
 
       callback.func.run();
@@ -182,7 +182,7 @@ public class TimedRobot extends IterativeRobotBase {
 
   /**
    * Return the system clock time in microseconds for the start of the current periodic loop. This
-   * is in the same time base as Timer.getFPGATimestamp(), but is stable through a loop. It is
+   * is in the same time base as Timer.getMonotonicTimestamp(), but is stable through a loop. It is
    * updated at the beginning of every periodic callback (including the normal periodic loop).
    *
    * @return Robot running time in microseconds, as of the start of the current periodic function.

wpilibj/src/main/java/org/wpilib/hardware/motor/MotorSafety.java

@@ -25,7 +25,7 @@ public abstract class MotorSafety {
 
   private double m_expiration = kDefaultSafetyExpiration;
   private boolean m_enabled;
-  private double m_stopTime = Timer.getFPGATimestamp();
+  private double m_stopTime = Timer.getMonotonicTimestamp();
   private final Object m_thisMutex = new Object();
   private static final Set<MotorSafety> m_instanceList = new LinkedHashSet<>();
   private static final Object m_listMutex = new Object();
@@ -83,7 +83,7 @@ public abstract class MotorSafety {
    */
   public void feed() {
     synchronized (m_thisMutex) {
-      m_stopTime = Timer.getFPGATimestamp() + m_expiration;
+      m_stopTime = Timer.getMonotonicTimestamp() + m_expiration;
     }
   }
 
@@ -116,7 +116,7 @@ public abstract class MotorSafety {
    */
   public boolean isAlive() {
     synchronized (m_thisMutex) {
-      return !m_enabled || m_stopTime > Timer.getFPGATimestamp();
+      return !m_enabled || m_stopTime > Timer.getMonotonicTimestamp();
     }
   }
 
@@ -138,7 +138,7 @@ public abstract class MotorSafety {
       return;
     }
 
-    if (stopTime < Timer.getFPGATimestamp()) {
+    if (stopTime < Timer.getMonotonicTimestamp()) {
       DriverStation.reportError(
           getDescription()
               + "... Output not updated often enough. See https://docs.wpilib.org/motorsafety for more information.",

wpilibj/src/main/java/org/wpilib/opmode/PeriodicOpMode.java

@@ -66,7 +66,7 @@ public abstract class PeriodicOpMode implements OpMode {
           startTime
               + offset
               + this.period
-              + (RobotController.getFPGATime() - startTime) / this.period * this.period;
+              + (RobotController.getMonotonicTime() - startTime) / this.period * this.period;
     }
 
     @Override
@@ -120,7 +120,7 @@ public abstract class PeriodicOpMode implements OpMode {
    * @param period period (in seconds) for callbacks to the periodic() function
    */
   protected PeriodicOpMode(double period) {
-    m_startTimeUs = RobotController.getFPGATime();
+    m_startTimeUs = RobotController.getMonotonicTime();
     m_period = period;
     m_watchdog = new Watchdog(period, this::printLoopOverrunMessage);
 
@@ -157,8 +157,8 @@ public abstract class PeriodicOpMode implements OpMode {
 
   /**
    * Return the system clock time in micrseconds for the start of the current periodic loop. This is
-   * in the same time base as Timer.getFPGATimestamp(), but is stable through a loop. It is updated
-   * at the beginning of every periodic callback (including the normal periodic loop).
+   * in the same time base as Timer.getMonotonicTimestamp(), but is stable through a loop. It is
+   * updated at the beginning of every periodic callback (including the normal periodic loop).
    *
    * @return Robot running time in microseconds, as of the start of the current periodic function.
    */
@@ -290,8 +290,8 @@ public abstract class PeriodicOpMode implements OpMode {
         break;
       }
 
-      long currentTime = RobotController.getFPGATime();
-      m_loopStartTimeUs = RobotController.getFPGATime();
+      long currentTime = RobotController.getMonotonicTime();
+      m_loopStartTimeUs = RobotController.getMonotonicTime();
 
       callback.func.run();
 

wpilibj/src/main/java/org/wpilib/system/RobotController.java

@@ -22,7 +22,7 @@ import org.wpilib.units.measure.Voltage;
 
 /** Contains functions for roboRIO functionality. */
 public final class RobotController {
-  private static LongSupplier m_timeSource = RobotController::getFPGATime;
+  private static LongSupplier m_timeSource = RobotController::getMonotonicTime;
 
   private RobotController() {
     throw new UnsupportedOperationException("This is a utility class!");
@@ -69,9 +69,9 @@ public final class RobotController {
   }
 
   /**
-   * Read the microsecond timestamp. By default, the time is based on the FPGA hardware clock in
-   * microseconds since the FPGA started. However, the return value of this method may be modified
-   * to use any time base, including non-monotonic and non-continuous time bases.
+   * Read the microsecond timestamp. By default, the time is based on the monotonic clock. However,
+   * the return value of this method may be modified to use any time base, including non-monotonic
+   * and non-continuous time bases.
    *
    * @return The current time in microseconds.
    */
@@ -80,9 +80,9 @@ public final class RobotController {
   }
 
   /**
-   * Read the microsecond timestamp. By default, the time is based on the FPGA hardware clock in
-   * microseconds since the FPGA started. However, the return value of this method may be modified
-   * to use any time base, including non-monotonic and non-continuous time bases.
+   * Read the microsecond timestamp. By default, the time is based on the monotonic clock. However,
+   * the return value of this method may be modified to use any time base, including non-monotonic
+   * and non-continuous time bases.
    *
    * @return The current time in a measure.
    */
@@ -91,21 +91,21 @@ public final class RobotController {
   }
 
   /**
-   * Read the microsecond timer from the FPGA.
+   * Read the microsecond monotonic timer.
    *
-   * @return The current time in microseconds according to the FPGA.
+   * @return The current monotonic time in microseconds.
    */
-  public static long getFPGATime() {
-    return HALUtil.getFPGATime();
+  public static long getMonotonicTime() {
+    return HALUtil.getMonotonicTime();
   }
 
   /**
-   * Read the microsecond timer in a measure from the FPGA.
+   * Read the microsecond monotonic timer in a measure.
    *
-   * @return The current time according to the FPGA in a measure.
+   * @return The current monotonic time in a measure.
    */
-  public static Time getMeasureFPGATime() {
-    return Microseconds.of(HALUtil.getFPGATime());
+  public static Time getMeasureMonotonicTime() {
+    return Microseconds.of(HALUtil.getMonotonicTime());
   }
 
   /**

wpilibj/src/main/java/org/wpilib/system/Timer.java

@@ -17,9 +17,9 @@ import org.wpilib.units.measure.Time;
  */
 public class Timer {
   /**
-   * Return the clock time in seconds. By default, the time is based on the FPGA hardware clock in
-   * seconds since the FPGA started. However, the return value of this method may be modified to use
-   * any time base, including non-monotonic time bases.
+   * Return the clock time in seconds. By default, the time is the time returned by
+   * getMonotonicTimestamp(). However, the return value of this method may be modified to use any
+   * time base, including non-monotonic time bases.
    *
    * @return Robot running time in seconds.
    */
@@ -28,13 +28,12 @@ public class Timer {
   }
 
   /**
-   * Return the system clock time in seconds. Return the time from the FPGA hardware clock in
-   * seconds since the FPGA started.
+   * Return the monotonic clock time in seconds.
    *
-   * @return Robot running time in seconds.
+   * @return Monotonic time in seconds.
    */
-  public static double getFPGATimestamp() {
-    return RobotController.getFPGATime() / 1000000.0;
+  public static double getMonotonicTimestamp() {
+    return RobotController.getMonotonicTime() / 1000000.0;
   }
 
   /**

wpilibj/src/main/java/org/wpilib/system/Tracer.java

@@ -38,7 +38,7 @@ public class Tracer {
 
   /** Restarts the epoch timer. */
   public final void resetTimer() {
-    m_startTime = RobotController.getFPGATime();
+    m_startTime = RobotController.getMonotonicTime();
   }
 
   /**
@@ -53,7 +53,7 @@ public class Tracer {
    * @param epochName The name to associate with the epoch.
    */
   public void addEpoch(String epochName) {
-    long currentTime = RobotController.getFPGATime();
+    long currentTime = RobotController.getMonotonicTime();
     m_epochs.put(epochName, currentTime - m_startTime);
     m_startTime = currentTime;
   }
@@ -71,7 +71,7 @@ public class Tracer {
    * @param output the stream that the output is sent to
    */
   public void printEpochs(Consumer<String> output) {
-    long now = RobotController.getFPGATime();
+    long now = RobotController.getMonotonicTime();
     if (now - m_lastEpochsPrintTime > kMinPrintPeriod) {
       StringBuilder sb = new StringBuilder();
       m_lastEpochsPrintTime = now;

wpilibj/src/main/java/org/wpilib/system/Watchdog.java

@@ -100,7 +100,7 @@ public class Watchdog implements Closeable, Comparable<Watchdog> {
    * @return The time in seconds since the watchdog was last fed.
    */
   public double getTime() {
-    return Timer.getFPGATimestamp() - m_startTime;
+    return Timer.getMonotonicTimestamp() - m_startTime;
   }
 
   /**
@@ -109,7 +109,7 @@ public class Watchdog implements Closeable, Comparable<Watchdog> {
    * @param timeout The watchdog's timeout in seconds with microsecond resolution.
    */
   public void setTimeout(double timeout) {
-    m_startTime = Timer.getFPGATimestamp();
+    m_startTime = Timer.getMonotonicTimestamp();
     m_tracer.clearEpochs();
 
     m_queueMutex.lock();
@@ -184,7 +184,7 @@ public class Watchdog implements Closeable, Comparable<Watchdog> {
 
   /** Enables the watchdog timer. */
   public void enable() {
-    m_startTime = Timer.getFPGATimestamp();
+    m_startTime = Timer.getMonotonicTimestamp();
     m_tracer.clearEpochs();
 
     m_queueMutex.lock();
@@ -247,7 +247,7 @@ public class Watchdog implements Closeable, Comparable<Watchdog> {
         Thread.currentThread().interrupt();
         break;
       }
-      long curTime = HALUtil.getFPGATime();
+      long curTime = HALUtil.getMonotonicTime();
 
       m_queueMutex.lock();
       try {