Step 1: Create your class

The first step to creating your Subsystem is setting up the structure for it. There should only be one instance of each Subsystem class. To do this, there is a couple lines of boilerplate you will need to add to the top of every subsystem class you create. Here is the subsystem class template:

public class MySubsystem extends Subsystem {
    // BOILERPLATE
    public static final MySubsystem INSTANCE = new MySubsystem();
    private MySubsystem() { }

    // USER CODE HERE
}

In this case, let's call our subsystem Lift.

Step 2: Create your motor

Next, we need to set up a motor to power our lift. This is easy to do using the MotorEx class. Let's start by creating a variable to store our motor. It should be of type MotorEx. Note that we aren't setting the value immediately; this is because we don't have access to the hardware map until an OpMode is initialized.

public MotorEx motor;

We also need a Controller, since we want to move our motor. Let's use a PID controller. I recommend using a P value of 0.005 to start, and leaving I and D at zero. You should come back and tune it later, though.

public PIDController controller = new PIDController(new PIDCoefficients(0.005, 0.0, 0.0));

Next, we need a name. This is the name specified in the hardwareMap, so that NextFTC can find the motor. I called mine lift_motor, so that's the name I'm using. Use whatever name you've set in your configuration:

public String name = "lift_motor";

Finally, the last step to setting up a motor is instantiating the motor in the initialize() function. Let's do that now:

@Override
public void initialize() {
    motor = new MotorEx(name);
}

That's all you need to do to create a motor in NextFTC! To recap:

• Every motor needs to be stored in a variable
• Every motor needs a Controller
• Every motor needs a name
• Every motor must be instantiated in the initialize function.

We're not quite done, though. We still need to create our first commands!

Step 3: Create commands

The last step when you create a Subsystem is to create the commands you'll be using. This process varies with each subsystem. Here, I'll walk you through creating three commands that each move the lift to a different height: toLow, toMiddle, and toHigh.

To control our motor, we will be using the RunToPosition command. In Java, the best way to create commands is by making functions that return instances of command classes.

Let's create our first RunToPosition command:

public Command toLow() {
    return new RunToPosition(motor, // MOTOR TO MOVE
            0.0, // TARGET POSITION, IN TICKS
            controller, // CONTROLLER TO IMPLEMENT
            this); // IMPLEMENTED SUBSYSTEM
}

Note the last parameter: subsystem. This is what tells NextFTC which commands should be allowed to run at the same time. If it weren't set, toLow would be able to run at the same time as other commands that use the Lift subsystem -- so there would be multiple things fighting to set the motor's power. Generally, you just need to pass this as the subsystem -- there are exceptions with more complicated custom commands.

Pretty easy, right? Let's duplicate it and update our function name and target position to create our other two commands:

public Command toMiddle() {
    return new RunToPosition(motor, // MOTOR TO MOVE
            500.0, // TARGET POSITION, IN TICKS
            controller, // CONTROLLER TO IMPLEMENT
            this); // IMPLEMENTED SUBSYSTEM
}

public Command toHigh() {
    return new RunToPosition(motor, // MOTOR TO MOVE
            1200.0, // TARGET POSITION, IN TICKS
            controller, // CONTROLLER TO IMPLEMENT
            this); // IMPLEMENTED SUBSYSTEM
}

Final result

That's it! You've created your first Subsystem! Here is the final result:

public class Lift extends Subsystem {
    // BOILERPLATE
    public static final Lift INSTANCE = new Lift();
    private Lift() { }

    // USER CODE
    public MotorEx motor;

    public PIDController controller = new PIDController(new PIDCoefficients(0.005, 0.0, 0.0));

    public String name = "lift_motor";

    public Command toLow() {
        return new RunToPosition(motor, // MOTOR TO MOVE
                0.0, // TARGET POSITION, IN TICKS
                controller, // CONTROLLER TO IMPLEMENT
                this); // IMPLEMENTED SUBSYSTEM
    }

    public Command toMiddle() {
        return new RunToPosition(motor, // MOTOR TO MOVE
                500.0, // TARGET POSITION, IN TICKS
                controller, // CONTROLLER TO IMPLEMENT
                this); // IMPLEMENTED SUBSYSTEM
    }

    public Command toHigh() {
        return new RunToPosition(motor, // MOTOR TO MOVE
                1200.0, // TARGET POSITION, IN TICKS
                controller, // CONTROLLER TO IMPLEMENT
                this); // IMPLEMENTED SUBSYSTEM
    }
    
    @Override
    public void initialize() {
        motor = new MotorEx(name);
    }
}