Timed actions and debugging

When nobody is holding a controller, our program still needs to know when an action should finish. A sensor can confirm success, and a timer can keep the program from trying forever if the expected event never happens.

The Timer¶

In your periodic example, self.timer = wpilib.Timer() creates a timer. restart() resets and starts it in autonomousInit. get() returns elapsed seconds. Autonomous requests collection while elapsed time is below two seconds, then requests zero. Piece detection may stop the motor sooner through set_intake.

"""Periodic intake example; launch through tools/run_robot.py."""
import wpilib
from examples.support.intake_io import IntakeSim


class Robot(wpilib.TimedRobot):
    def robotInit(self):
        if wpilib.RobotBase.isReal():
            raise RuntimeError("This course example is simulation-only")
        self.io = IntakeSim()
        self.timer = wpilib.Timer()
        wpilib.SmartDashboard.putNumber("Intake request", 0.0)
        wpilib.SmartDashboard.putBoolean("Piece available", True)

    def set_intake(self, request):
        if self.io.detected and request > 0:
            self.io.set_output(0.0)
        else:
            self.io.set_output(request)

    def teleopPeriodic(self):
        request = wpilib.SmartDashboard.getNumber("Intake request", 0.0)
        self.set_intake(request)

    def autonomousInit(self):
        self.timer.restart()

    def autonomousPeriodic(self):
        if self.timer.get() < 2.0:
            self.set_intake(0.5)
        else:
            self.set_intake(0.0)

    def disabledInit(self):
        self.io.set_output(0.0)

    def simulationPeriodic(self):
        self.io.enabled = self.isEnabled()
        self.io.piece_available = wpilib.SmartDashboard.getBoolean("Piece available", True)
        self.io.step()
        wpilib.SmartDashboard.putBoolean("Has piece", self.io.detected)
        wpilib.SmartDashboard.putNumber("Intake output", self.io.output)

This is the full maintained example. Compare the callbacks to your copy rather than pasting it over your work. The simulation callbacks are supplied infrastructure; you should understand their purpose without having to implement a simulator.

Both Outcomes¶

Restart with a piece available, enable autonomous, and observe detection stop the intake. Then restart with Piece available false. It should stop after about two seconds without reporting a held piece. A timeout means time ran out; it does not mean acquisition succeeded. That distinction matters before any later action that assumes the robot has a piece.

Small Change¶

Change the acquisition limit to one second. Then add a dashboard status string using wpilib.SmartDashboard.putString("Intake status", text). Use three messages: collecting, piece detected, and timed out. Choose the message from observed conditions; don’t report success merely because the timer expired.

Diagnosing Faults¶

Temporarily change the sensor rule so it blocks negative output instead of positive output. Predict the symptom, reproduce it, inspect request/output/detection, then repair the comparison. Use the same reproduce–inspect–change–rerun process from the first debugging lesson.

To finish this stage, run teleop collection and release, timed autonomous with and without a piece, and disable during motion. Write down what you expect in each case and compare it with the result. Explain why resetting the timer in every periodic call would prevent timeout. Commit your working version before reorganizing it in the next stage.