Robot Architecture

How a robot program is organized and how it runs.

How the Robot Runs

When you turn on the robot, here is what happens:

graph LR
    A[Power On] --> B[Code starts]
    B --> C[robotInit - setup once]
    C --> D[autonomousInit]
    D --> E[autonomousPeriodic 50x/sec]
    E --> F[teleopInit]
    F --> G[teleopPeriodic 50x/sec]
    G --> H[disabled]
    H --> D

The Robot Lifecycle

Method	When It Runs	What To Put Here
robotInit()	Once when robot turns on	Create subsystems, load settings
autonomousInit()	Once when auto starts	Set targets for auto routine
autonomousPeriodic()	50x/sec during auto	Check sensors, run autonomous logic
teleopInit()	Once when teleop starts	Prepare for driver control
teleopPeriodic()	50x/sec during teleop	Read joysticks, drive the robot

Init vs Periodic: Init runs once (like pressing "start" on a microwave). Periodic runs 50 times per second (like the microwave constantly checking if your food is done).

Project Structure

How the XBot codebase is organized:

TeamXbot2026/
├── src/
│   └── main/java/competition/
│       ├── electrical_contract/    # Wiring definitions (which motor on which port)
│       ├── subsystems/             # Robot mechanisms (drive, shooter, intake)
│       │   ├── drive/
│       │   ├── shooter/
│       │   └── intake/
│       ├── operator_interface/     # Gamepad button bindings
│       └── Robot.java              # Main robot class (lifecycle)

What is a Subsystem?

A subsystem represents one physical part of the robot. Think of it like an organ in a body -- each organ has a specific job:

• DriveSubsystem = legs (moves the robot)
• ShooterSubsystem = arm (shoots game pieces)
• IntakeSubsystem = hand (picks up game pieces)

Each subsystem controls its own motors and sensors, and provides methods for other code to use.

The Entry Point

// Main.java -- the first code that runs when the robot turns on
public final class Main {
    public static void main(String... args) {
        RobotBase.startRobot(Robot::new);
    }
}

You should never need to modify this file. It is the same for every FRC robot.

The Robot Class

public class Robot extends BaseRobot {
    @Override
    protected void initializeSystems() {
        super.initializeSystems();
        // Connect buttons to commands, set default behaviors
        getInjectorComponent().subsystemDefaultCommandMap();
        getInjectorComponent().operatorCommandMap();
    }
}

This is where everything gets connected together. You will learn more about this as you progress through the curriculum.

Core Programming vs Vision

Team	What They Work On
Core Programming	Drive, shooter, intake, autonomous, robot infrastructure
Vision (future)	AprilTag detection, camera processing, path planning

You will start on Core Programming. Vision is a separate team you can join later.

---

Quiz

Q1: How many times per second does teleopPeriodic() run?

• [ ] A) Once
• [ ] B) 5 times per second
• [ ] C) 50 times per second
• [ ] D) 500 times per second

Answer

C) 50 times per second

The robot control loop runs at 50Hz, meaning periodic() methods are called every 20 milliseconds. This is fast enough to feel responsive to the driver.

Q2: What does robotInit() do?

• [ ] A) Runs 50 times per second
• [ ] B) Runs once when the robot turns on
• [ ] C) Runs when a button is pressed
• [ ] D) Runs when the match ends

Answer

B) Runs once when the robot turns on

robotInit() runs exactly once at startup to set up subsystems, load settings, and prepare the robot.

Q3: What does a subsystem represent?

• [ ] A) A file in the project
• [ ] B) One physical mechanism on the robot
• [ ] C) A gamepad button
• [ ] D) A type of motor

Answer

B) One physical mechanism on the robot

Each subsystem controls one part of the robot (drive, shooter, intake, etc.) with its own motors and sensors.