Lesson 6.5: Challenge — Build a Non-Blocking Timer for Parallel Mechanism Control

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Technical Context

"Blocking" code (using sleep() or empty while loops) prevents a robot from performing parallel tasks. A high-performance robot must be able to drive toward a target while simultaneously raising a lift. A non-blocking timer loop allows the program to check multiple conditions — time, sensors, and encoders — in a single loop cycle, enabling true parallel mechanism control.

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How Non-Blocking Timing Lets Mechanisms Work Together

This challenge integrates while(opModeIsActive()) and getRuntime() comparisons from the previous lessons. The key insight is that the loop body runs many times per second. Instead of waiting inside the loop, the code simply checks whether a condition is met on each pass and acts accordingly — all other hardware logic continues to run uninterrupted every cycle.

This is the foundation of state machine transitions and parallel autonomous movement, used by championship-level FTC teams.

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Annotated Code

package org.firstinspires.ftc.teamcode;

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

@TeleOp(name="Parallel_Control_Demo")
public class ParallelControlDemo extends LinearOpMode {

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

        waitForStart();

        // Set a target time: run the lift for 2 seconds after match starts
        double liftTargetTime = getRuntime() + 2.0;

        while (opModeIsActive()) {
            // Action 1: Drive responds to gamepad every cycle — never blocked
            driveMotor.setPower(-gamepad1.left_stick_y);

            // Action 2: Lift only runs if the timer window is still open
            if (getRuntime() < liftTargetTime) {
                liftMotor.setPower(1.0);
            } else {
                liftMotor.setPower(0.0);
            }

            telemetry.addData("Lift Active", getRuntime() < liftTargetTime);
            telemetry.update();
        }
    }
}

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Fill-in-the-Blank Practice

1. Using sleep() is discouraged because it __________ the entire program thread from updating other hardware.
2. A __________ timer loop is necessary to allow parallel mechanism control.
3. To trigger an event after 5 seconds without stopping the robot, you would compare getRuntime() against a __________ captured at the start of the event.

Show answers

1. blocks
2. non-blocking
3. timestamp (a double variable storing getRuntime() + 5.0)

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Template Challenge

Robot Scenario: Create a LinearOpMode that runs an "intake" motor for 3 seconds while simultaneously allowing the robot to move with gamepad1.left_stick_y on a "drive" motor. Neither mechanism should block the other.

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="Parallel_Action_Challenge")
public class ParallelAction extends LinearOpMode {

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

        waitForStart();

        // INSERT CODE HERE: Create a timestamp 3 seconds in the future
        double intakeEnd = // INSERT VALUE HERE

        while (opModeIsActive()) {
            // INSERT CODE HERE: Set drive power from gamepad1.left_stick_y

            // INSERT CODE HERE: Use an 'if' to run intake ONLY if time remains
            {
                intake.setPower(1.0);
            } else {
                intake.setPower(0.0);
            }

            telemetry.update();
        }
    }
}

Show answer

double intakeEnd = getRuntime() + 3.0;

while (opModeIsActive()) {
    drive.setPower(-gamepad1.left_stick_y);

    if (getRuntime() < intakeEnd) {
        intake.setPower(1.0);
    } else {
        intake.setPower(0.0);
    }

    telemetry.update();
}

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