Lesson 2.3: Running Real-Time Robot Logic Inside loop()

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Context

The loop() method controls the robot's performance during the match. Because it runs at a high frequency (approximately 50 times per second), it allows for smooth movement and rapid sensor polling. Efficiency in this method is critical, any "blocking" code (like a sleep command) will freeze the robot and could cause a communication timeout with the Driver Station.

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The loop() Lifecycle

In an OpMode, the loop() method is executed repeatedly after the driver presses the "Play" button and until they press "Stop". It usually follows a sensing → thinking → acting cycle: it reads the latest values from the Gamepads or sensors, calculates the necessary power adjustments, and commands the Control Hub's motor controllers to update voltage outputs.

Since loop() is non-blocking, it is ideal for TeleOp where driver inputs are changing in real-time.

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Annotated Code

@TeleOp(name="Loop_Demo")
public class LoopDemo extends OpMode {

    @Override
    public void init() {
        telemetry.addData("Status", "Ready to Play");
    }

    @Override
    public void loop() {
        // This logic runs ~50x a second to check for driver input
        double drivePower = -gamepad1.left_stick_y;

        // Streaming hardware data back to the DS for real-time monitoring
        telemetry.addData("Motor Command", drivePower);
        telemetry.addData("Cycle Time", getRuntime());
    }
}

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Fill-in-the-Blank Practice

1. The loop() method runs repeatedly at a frequency of approximately __________ times per second.
2. If you put a long delay inside loop(), you risk losing connection to the __________ Station.
3. The robot stops executing the loop() method once the driver presses the __________ button.

Show answers

1. 50
2. Driver Station
3. Stop

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Challenge

You need to create a simple diagnostic that shows the status of the "A" button on gamepad1 during the entire match.

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

@Override
public void loop() {
    telemetry.addData("Button A", gamepad1.a);
    telemetry.update();
}

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