Lesson 6.3: Timing Robot Actions with getRuntime()

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Technical Context

Standard sleep() commands block the entire thread, preventing the robot from reading sensor data or reacting to gamepad inputs during the sleep period. Comparing loop iterations against getRuntime() allows for "non-blocking" timing, enabling the robot to perform multiple hardware tasks simultaneously within the same loop cycle.

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How getRuntime() Helps You Time Actions Without Guessing

The getRuntime() method returns a double representing the seconds elapsed since the OpMode was initialized. By capturing a "start time" timestamp and comparing it to the current getRuntime() value inside a while or if statement, the programmer creates a timed window for hardware to operate — without freezing any other logic.

The key pattern is: capture a target timestamp, then check against it each loop cycle.

double targetTime = getRuntime() + 2.0; // 2 seconds from now

The clock increments in sub-milliseconds, so you must use < (less than) rather than == for the comparison — the current time will almost never land on the exact target value.

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Annotated Code

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.eventloop.opmode.Autonomous;
import com.qualcomm.robotcore.hardware.DcMotor;

@Autonomous(name="Timed_Drive_Demo")
public class TimedDriveDemo extends LinearOpMode {

    @Override
    public void runOpMode() {
        DcMotor driveMotor = hardwareMap.get(DcMotor.class, "drive");

        waitForStart();

        // Set a timestamp 2 seconds in the future
        double targetTime = getRuntime() + 2.0;

        // Drive forward until the 2-second window closes
        while (opModeIsActive() && getRuntime() < targetTime) {
            driveMotor.setPower(0.5);
            telemetry.addData("Time Remaining", targetTime - getRuntime());
            telemetry.update();
        }

        driveMotor.setPower(0); // Stop cleanly after the timed move
    }
}

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Fill-in-the-Blank Practice

1. The getRuntime() method returns the time as a __________ data type.
2. When comparing time, it is critical to use the __________ operator instead of == because the clock increments in sub-milliseconds.
3. To reset the internal clock to zero at the start of the match, use the __________ method.

Show answers

1. double
2. < (less than)
3. resetRuntime()

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Template Challenge

Robot Scenario: The robot must run a "test_motor" for exactly 1.5 seconds when the user presses the 'X' button, but it must not use sleep().

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.OpMode;
import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
import com.qualcomm.robotcore.hardware.DcMotor;

@TeleOp(name="Non_Blocking_Timer")
public class NonBlockingTimer extends OpMode {

    private DcMotor test_motor;
    private double endTime = 0;

    @Override
    public void init() {
        test_motor = hardwareMap.get(DcMotor.class, "test_motor");
    }

    @Override
    public void loop() {
        if (gamepad1.x) {
            // INSERT CODE HERE: Capture the current runtime plus 1.5 seconds into 'endTime'
        }

        if (getRuntime() < endTime) {
            test_motor.setPower(1.0);
        } else {
            test_motor.setPower(0.0);
        }

        telemetry.addData("Motor Active", getRuntime() < endTime);
        telemetry.update();
    }
}

Show answer

if (gamepad1.x) {
    endTime = getRuntime() + 1.5;
}

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