Lesson 2.2: Setting Up Hardware in init() Before the Match Starts

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Context

The init() method is the hardware setup phase. It prevents NullPointerException crashes by ensuring that every motor and sensor object is linked to a physical port on the Control Hub before the match begins. Failure to properly instantiate hardware here will result in the robot failing to respond when the "Play" button is pressed.

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What is the init() Method?

The init() method is a callback executed exactly once when the driver presses the "INIT" button on the Driver Station. This is the stage where the program accesses the hardwareMap, a built-in object that acts as a registry for all configured devices.

By using hardwareMap.get(), you associate a Java variable with the specific configuration name assigned in the Robot Controller settings. This is also where you define the initial state of components, such as setting DcMotors to RUN_USING_ENCODER mode.

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Annotated Code

@TeleOp(name="Init_Demo")
public class InitDemo extends OpMode {

    // Declaring the object variable before initialization
    private DcMotor armMotor;

    @Override
    public void init() {
        // Linking the Java variable to the physical Control Hub Port 0
        // The string "arm" must match the Hub configuration exactly
        armMotor = hardwareMap.get(DcMotor.class, "arm");

        // Setting the hardware to a known safe state
        armMotor.setPower(0);
        telemetry.addData("Hardware", "Arm Motor Map Successful");
    }

    @Override
    public void loop() {}
}

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Fill-in-the-Blank Practice

1. The init() method is executed exactly __________ time(s) when the driver presses the INIT button.
2. To link a physical motor to a code variable, you must call the __________ method from the hardwareMap object.
3. Variables for hardware like motors should be declared at the __________ level so they can be accessed by both init() and loop().

Show answers

1. one (1)
2. get()
3. class level (as fields, outside of any method)

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Challenge

You need to prepare a Servo named "claw" for the match. Use the init() method to map it and ensure it is ready to move once the match starts.

Unit 2 simulator

Supports `init()`, `init_loop()`, `start()`, `loop()`, and `stop()`.

Reads `@TeleOp`, `@Autonomous`, `@Disabled`, telemetry, and `gamepad1`.

Handles local variables, simple math, `resetRuntime()`, and `getRuntime()`.

Does not execute hardware, `gamepad2`, `else` blocks, or loop structures.

Show answer

private Servo claw;

@Override
public void init() {
    claw = hardwareMap.get(Servo.class, "claw_servo");
    telemetry.addData("Status", "Claw Initialized");
}

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