Servo Control

Motors are great for wheels and lifts, but many robot mechanisms need something different: a device that moves to a specific position and holds it there. That is exactly what a servo does. In this lesson, you will learn how servos work and how to control them with gamepad buttons.

Servos vs. Motors

Motors and servos are both actuators, but they work very differently:

Using Servos in Code

Servos follow the same hardware map pattern as motors:

import com.qualcomm.robotcore.hardware.Servo;
Servo myServo = hardwareMap.get(Servo.class, "myServo");

Then, to move the servo:

myServo.setPosition(1.0);  // Move to maximum position
myServo.setPosition(0.0);  // Move to minimum position
myServo.setPosition(0.5);  // Move to midpoint

The position value is a double between 0.0 and 1.0:

• 0.0 = one end of the servo's range (e.g., claw fully open)
• 1.0 = the other end of the servo's range (e.g., claw fully closed)
• 0.5 = midpoint

Controlling Servos with Buttons

Joysticks are great for proportional control (like drive motors), but servos often have discrete states: open/closed, up/down, extended/retracted. Gamepad buttons are perfect for this.

Here is a common pattern:

while (opModeIsActive()) {
    if (gamepad1.a) {
        clawServo.setPosition(1.0);  // Close the claw
    } else if (gamepad1.b) {
        clawServo.setPosition(0.0);  // Open the claw
    }
}

When the driver presses A, the claw closes. When they press B, the claw opens. If neither button is pressed, the servo holds its last commanded position.

A Note About Servo Timing

Servos do not move instantly. When you call setPosition(), the servo begins moving toward that position, but it takes time to get there (typically a few hundred milliseconds). The FTC SDK handles this automatically -- you just set the target and the servo does the rest.

This means you do not need to worry about waiting for the servo to finish moving before doing other things. The servo moves in the background while your code continues.

Your Exercise

You have a servo named "testServo". The simulated gamepad has the A button pressed (gamepad1.a is true).

Your task:

1. Get the servo from the hardware map.
2. After waitForStart(), check if gamepad1.a is pressed. If so, set the servo position to 1.0.
3. Also check if gamepad1.b is pressed. If so, set the servo position to 0.0.

Give it a try!