Lesson 4.5: Build a Complete Arcade Drive

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Technical Context

An arcade drive controls a differential drivetrain with one forward command and one turn command. The program mixes those two commands into separate left and right motor powers:

left power  = forward + turn
right power = forward - turn

Forward input raises both sides together. Turn input raises one side while lowering the other. Unlike sensitivity shaping, this mixing step is what actually makes the robot steer.

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How to Build an Arcade Drive That Feels Good

A competition-ready arcade drive combines every Unit 4 input technique in a deliberate order:

1. Read forward and turn axes.
2. Apply a deadzone to prevent joystick drift.
3. Toggle precision mode on the press edge, not during every loop that the button remains held.
4. Shape the inputs when precision mode is active.
5. Mix forward and turn into left and right power.
6. Apply the trigger speed limit and clip both results to the legal -1.0 to 1.0 motor range.
7. Command the motors and report the final values.

The press edge requires the current and previous button values. gamepad1.a && !previousA is true for only the first loop after A is pressed. At the end of the loop, save gamepad1.a into previousA for the next comparison.

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Annotated Code

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;
import com.qualcomm.robotcore.util.Range;

@TeleOp(name="Arcade_Drive_System", group="Practice")
public class ArcadeDrive extends OpMode {

    private DcMotor leftDrive;
    private DcMotor rightDrive;
    private boolean precisionMode = true;
    private boolean previousA = false;

    private static final double DEADZONE = 0.10;

    @Override
    public void init() {
        leftDrive  = hardwareMap.get(DcMotor.class, "left_drive");
        rightDrive = hardwareMap.get(DcMotor.class, "right_drive");
        leftDrive.setPower(0.0);
        rightDrive.setPower(0.0);
    }

    double squareInputWithSign(double input) {
        return input * input * Math.signum(input);
    }

    @Override
    public void loop() {
        double forward = -gamepad1.left_stick_y;
        double turn = gamepad1.right_stick_x;

        if (Math.abs(forward) < DEADZONE) forward = 0.0;
        if (Math.abs(turn) < DEADZONE) turn = 0.0;

        // Toggle once per press. Holding A does not keep flipping the mode.
        if (gamepad1.a && !previousA) {
            precisionMode = !precisionMode;
        }
        previousA = gamepad1.a;

        if (precisionMode) {
            forward = squareInputWithSign(forward);
            turn = squareInputWithSign(turn);
        }

        // Right trigger progressively limits top speed from 100% to 30%.
        double speedLimit = 1.0 - (0.70 * gamepad1.right_trigger);

        double leftPower  = Range.clip((forward + turn) * speedLimit, -1.0, 1.0);
        double rightPower = Range.clip((forward - turn) * speedLimit, -1.0, 1.0);

        leftDrive.setPower(leftPower);
        rightDrive.setPower(rightPower);

        telemetry.addData("Precision Mode", precisionMode);
        telemetry.addData("Left Power", leftPower);
        telemetry.addData("Right Power", rightPower);
        telemetry.update();
    }
}

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Fill-in-the-Blank Practice

1. Arcade drive calculates left power with forward ______ turn and right power with forward ______ turn.
2. A button toggle must compare the current button value with the __________ value so it changes only once per press.
3. Range.__________() keeps calculated motor power between the minimum and maximum legal values.

Show answers

1. plus, minus
2. previous
3. clip

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Simulator Practice

Robot Scenario: Finish the two-motor arcade drive. Apply deadzones, toggle precision mode only on the A-button press edge, mix forward and turn into separate left and right powers, limit both with the right trigger, and send the final values to the motors and telemetry.

1.Complete the codeWork in fullscreen when you need more room for the editor and visualizer. Where file tabs are available, hover over the tab strip and choose + to create a file or reuse saved code.

2.Run the lifecyclePress Init, then Start. Use the available gamepad or scene controls.

3.Debug the behaviorCheck telemetry, motion, requirements, and hints before opening the answer.

Telemark Unit 4 Simulator

Supports buttons, joysticks, triggers, bumpers, and D-pad input.

Shows live input values, basic telemetry, deadzones, and curve visualization when relevant.

Lesson 4.5 also compiles mapped motors and shows the power produced by the arcade-drive mix.

Show answer

// Use the complete annotated implementation above to compare each stage:
// input -> deadzone -> press-edge mode -> curve -> arcade mix -> clip -> motors.

A Team Delegates the Finished Drive Command

Titan Robotics Club calculates its driver inputs before choosing holonomic or arcade drive. This lesson uses the arcade branch directly:

double forward = shapeInput(-gamepad1.left_stick_y);
double turn = shapeInput(gamepad1.right_stick_x);
robot.drive.arcadeDrive(forward, turn);

The source's input array, scaling arguments, and framework object names were shortened. The order remains the same: shape the inputs, then send one drive command. Adapted from Team 3543 Titan Robotics Club's FtcTeleOp.java at a pinned commit under the MIT License.

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