Programming a Motor with a Gamepad

Driving Motors with the Gamepad

In the previous section you learned how to set the motor to run at a specific power level in a specific direction. However, in most applications, it will be necessary to control the motor with a gamepad, to easily change the direction or power level of a mechanism.

We are able to use a button to set the motor to a specific power or we can program it so it changes based on the direction of one of the gamepad's joysticks!

Using our existing test_motor.setPower(1); we can replace the value of 1 with this.gamepad1.left_stick_y;

// run until the end of the match (driver presses STOP)
 
while (opModeIsActive()) {
            test_motor.setPower(this.gamepad1.left_stick_y);
            telemetry.addData("Status", "Running");
            telemetry.update();
        }

Now the power of our motor will be set in response to the position of the gamepad's left joystick as it along the y-axis!

Quick Check!

Build your OpMode and test it out with your gamepad! Think about the following questions while testing:

• What happens when you move the left joystick up a small amount versus a large amount?

• What happens if you move the joystick to the left or right along the X-axis?

• What happens if you move the joystick at a diagonal or rotate it 360 degrees?

You may notice that when moving along the X-axis nothing happens at the moment. However, once the joystick hits an angle near the Y-axis vertices the motor may start to jitter and spin.

Adjusting Y-axis Direction

When you tested your program, did the motor spin the expected direction while moving the joystick up or down?

In the FTC SDK for most controllers the Y value of a joystick ranges from -1 when a joystick is in its topmost position, to +1 when a joystick is in its bottommost position.

That may be a little confusing to control, but we can add a negative symbol, or negation operator, to the line of code to change the direction of the motor in relation to the gamepad.

// run until the end of the match (driver presses STOP)
 
while (opModeIsActive()) {
            test_motor.setPower(-this.gamepad1.left_stick_y);
            telemetry.addData("Status", "Running");
            telemetry.update();
        }