Linear vs Iterative OpModes

beginner40 min

OpMode Types in FTC

FTC supports two main OpMode types: LinearOpMode and Iterative OpMode. Understanding the difference helps you choose the right structure for your code.

A LinearOpMode runs your code from top to bottom, like a script. An Iterative OpMode runs your code in a loop, giving you more control over timing and state.

See: gm0: OpMode Types

Key Differences

LinearOpMode vs Iterative OpMode:

LinearOpMode: Code runs sequentially, like a script.
Iterative OpMode: Code runs in repeated loop() calls.
LinearOpMode: Easier for beginners and autonomous routines.
Iterative OpMode: More control, better for advanced TeleOp.

LinearOpMode Example

@TeleOp(name = "LinearTeleOp")
public class LinearTeleOp extends LinearOpMode {
    private DcMotor leftDrive, rightDrive;

    @Override
    public void runOpMode() {
        leftDrive = hardwareMap.get(DcMotor.class, "left_drive");
        rightDrive = hardwareMap.get(DcMotor.class, "right_drive");
        waitForStart();
        while (opModeIsActive()) {
            double leftPower = -gamepad1.left_stick_y;
            double rightPower = -gamepad1.right_stick_y;
            leftDrive.setPower(leftPower);
            rightDrive.setPower(rightPower);
            telemetry.addData("Left Power", leftPower);
            telemetry.addData("Right Power", rightPower);
            telemetry.update();
        }
    }
}

Iterative OpMode Example

@TeleOp(name = "IterativeTeleOp")
public class IterativeTeleOp extends OpMode {
    private DcMotor leftDrive, rightDrive;

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

    @Override
    public void loop() {
        double leftPower = -gamepad1.left_stick_y;
        double rightPower = -gamepad1.right_stick_y;
        leftDrive.setPower(leftPower);
        rightDrive.setPower(rightPower);
        telemetry.addData("Left Power", leftPower);
        telemetry.addData("Right Power", rightPower);
        telemetry.update();
    }
}

When to Use Each Type

Choose based on your needs:

Use LinearOpMode for simple autonomous or TeleOp routines.
Use Iterative OpMode for advanced TeleOp with state machines or timing.
Start with LinearOpMode if you are new to FTC.
Convert to Iterative OpMode as your code grows more complex.

Converting Between Types

You can convert a LinearOpMode to an Iterative OpMode by moving your logic into the loop() method and managing state with variables. For example, if you have a sequence of actions in LinearOpMode, you can use a state variable in Iterative OpMode to step through them.

Next Steps

Telemetry Logging Basic Robot Control

Practice: OpMode Types

Try these to reinforce your understanding:

Write a LinearOpMode that drives a motor.
Convert it to an Iterative OpMode.
Compare the structure and behavior of both types.

Write a LinearOpMode that drives a motor

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

@TeleOp(name = "LinearMotorControl")
public class LinearMotorControl extends LinearOpMode {
    private DcMotor driveMotor;

    @Override
    public void runOpMode() {
        // Initialize hardware
        driveMotor = hardwareMap.get(DcMotor.class, "drive_motor");
        
        // Show initialization status
        telemetry.addData("Status", "Initialized");
        telemetry.update();
        
        // Wait for game to start
        waitForStart();
        
        // Main loop - runs sequentially
        while (opModeIsActive()) {
            // Read gamepad input
            double power = -gamepad1.left_stick_y;
            
            // Drive motor
            driveMotor.setPower(power);
            
            // Show telemetry
            telemetry.addData("Motor Power", power);
            telemetry.addData("Status", "Running");
            telemetry.update();
        }
    }
}

Convert it to an Iterative OpMode

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

@TeleOp(name = "IterativeMotorControl")
public class IterativeMotorControl extends OpMode {
    private DcMotor driveMotor;

    @Override
    public void init() {
        // Initialize hardware - called once at start
        driveMotor = hardwareMap.get(DcMotor.class, "drive_motor");
        
        // Show initialization status
        telemetry.addData("Status", "Initialized");
        telemetry.update();
    }

    @Override
    public void loop() {
        // Main loop - called repeatedly
        // Read gamepad input
        double power = -gamepad1.left_stick_y;
        
        // Drive motor
        driveMotor.setPower(power);
        
        // Show telemetry
        telemetry.addData("Motor Power", power);
        telemetry.addData("Status", "Running");
        telemetry.update();
    }
}

Compare the structure and behavior of both types

                  // Key Differences:
//
// LINEAR OPMODE:
// - Extends LinearOpMode
// - All code in runOpMode() method
// - Runs sequentially like a script
// - Can use waitForStart() and sleep()
// - Good for beginners and simple routines
//
// ITERATIVE OPMODE:
// - Extends OpMode
// - Separate init() and loop() methods
// - init() runs once, loop() runs repeatedly
// - More control over timing and state
// - Better for advanced TeleOp and state machines
//
// Both achieve the same result but with different structures!