CRServo: Continuous Rotation Servo

Standard servos move to a specific angle and hold it. A continuous rotation servo (CRServo) does something fundamentally different: it spins continuously, like a motor, but uses servo-style wiring and the REV Hub's servo ports. CRServos are a great fit for intake rollers, conveyor belts, and other mechanisms that just need to spin.

Standard Servo vs. CRServo

Feature	Servo	CRServo
Control input	Position (0.0 to 1.0)	Power (-1.0 to 1.0)
Output	Holds an angle	Spins continuously
API method	`setPosition(double)`	`setPower(double)`
Use case	Arms, claws, flippers	Intake rollers, belts

A standard Servo has an internal gear and feedback system to hold a target position. A CRServo has neither -- it simply converts your power command into rotation speed and direction. This also means you cannot read back its position.

The CRServo API

Getting a CRServo from the Hardware Map

CRServo intake = hardwareMap.get(CRServo.class, "intake");

The name "intake" must match the name configured in the Driver Station's hardware map for the servo port.

Controlling Power

intake.setPower(1.0);    // Full speed forward
intake.setPower(-1.0);   // Full speed reverse (eject)
intake.setPower(0.0);    // Stop
intake.setPower(0.5);    // Half speed forward

The power range is exactly -1.0 to 1.0, just like DcMotor.setPower().

Common Use Cases

Intake Roller

An intake roller pulls game elements into the robot. Forward power intakes; reverse power ejects.

if (gamepad1.right_bumper) {
    intake.setPower(1.0);    // Intake
} else if (gamepad1.left_bumper) {
    intake.setPower(-1.0);   // Eject
} else {
    intake.setPower(0.0);    // Off
}

Trigger-Based Control

Triggers give you analog input, which works naturally for intake control. Right trigger intakes, left trigger ejects:

intake.setPower(gamepad1.right_trigger - gamepad1.left_trigger);

Trigger values are in the range [0.0, 1.0]. The subtraction gives you:

Right trigger only (0.8 - 0.0 = 0.8): intake at 80%
Left trigger only (0.0 - 1.0 = -1.0): full reverse eject
Both triggers held (0.5 - 0.5 = 0.0): they cancel out, servo stops
Neither trigger (0.0 - 0.0 = 0.0): servo stops

This is a compact one-liner that handles all four states cleanly.

Direction Reversal

If the roller spins the wrong way for your wiring, reverse it without rewiring:

import com.qualcomm.robotcore.hardware.DcMotorSimple;
intake.setDirection(DcMotorSimple.Direction.REVERSE);

CRServo uses the same Direction enum as DcMotor. Set this in init() alongside your other hardware setup.

Full Example: Intake Control in TeleOp

@Override
public void runOpMode() {
    CRServo intake = hardwareMap.get(CRServo.class, "intake");
// Reverse if roller spins the wrong way
    // intake.setDirection(DcMotorSimple.Direction.REVERSE);
telemetry.addData("Status", "Ready");
    telemetry.update();
waitForStart();
while (opModeIsActive()) {
        // Trigger-based intake control
        double intakePower = gamepad1.right_trigger - gamepad1.left_trigger;
        intake.setPower(intakePower);
telemetry.addData("Intake Power", intakePower);
        telemetry.addData("Right Trigger", gamepad1.right_trigger);
        telemetry.addData("Left Trigger",  gamepad1.left_trigger);
        telemetry.update();
    }
}

Using Multiple CRServos

If your intake uses two rollers on opposite sides of the robot, one will need to be reversed so both push game elements in the same direction:

CRServo leftIntake  = hardwareMap.get(CRServo.class, "leftIntake");
CRServo rightIntake = hardwareMap.get(CRServo.class, "rightIntake");
rightIntake.setDirection(DcMotorSimple.Direction.REVERSE);
// Then both can receive the same power command
double power = gamepad1.right_trigger - gamepad1.left_trigger;
leftIntake.setPower(power);
rightIntake.setPower(power);

CRServo vs. DcMotor: Which Should You Use?

Both can spin continuously, so when do you choose one over the other?

Use CRServo when the mechanism is light, low-torque, and you want to use a servo port (not a motor port). Servo ports can power up to 6 servos independently.
Use DcMotor when you need more torque, more precise speed control, or you want encoder feedback to know how far it has spun.

For most FTC intake rollers, a CRServo is the right choice -- they are compact, simple, and the servo port is conveniently located on the REV Hub near where the mechanism is mounted.

Your Exercise

Control a CRServo named "intake" with gamepad1. Use the trigger-based formula: intake.setPower(gamepad1.right_trigger - gamepad1.left_trigger). In the sandbox, right_trigger = 0.8 and left_trigger = 0.0, so the servo should receive a power command of 0.8 - 0.0 = 0.8.