FTC Java Programming with REV Robotics: A Step-by-Step Guide

1. Setting Up the Development Environment

Before coding, you need to install and set up the necessary tools for programming in Java.

Step 1.1: Install Android Studio

FTC Java development uses Android Studio to write and upload code to your robot.

• Go to the Android Studio download page.
• Download and install the latest stable version for your operating system.
• Follow the instructions for installation, then open Android Studio once installed.

Step 1.2: Install the FTC SDK

FTC provides a Software Development Kit (SDK) that contains all the necessary libraries and examples.

• Visit the FTC SDK GitHub page.
• Download the SDK as a ZIP file or clone the repository using Git:

git clone https://github.com/FIRST-Tech-Challenge/FtcRobotController.git

• Open the SDK in Android Studio: File > Open, and select the folder where the SDK is located.

2. Understanding REV Robotics Hardware

Step 2.1: REV Control Hub and Expansion Hub

• The Control Hub is the “brain” of the robot, managing communication between the software and hardware.
• The Expansion Hub connects additional motors, servos, and sensors to your robot.
• Ensure you’ve connected the REV hubs and the power module according to the REV Robotics hardware guide.

3. Configuring Your Robot in FTC Dashboard

Step 3.1: Access the FTC Dashboard

• Turn on your robot and connect it to the same Wi-Fi network as your development computer.
• Open a browser and go to the robot’s IP address (usually 192.168.43.1) to access the robot's configuration dashboard.
• Set up the motor controllers, sensors, and other peripherals. For example:
• Name your motors, such as “left_drive” and “right_drive”.
• Name your servos, like “arm_servo”.

4. Writing Your First FTC Java Program

Now that your environment is ready, it’s time to write a basic Java program.

Step 4.1: Create an OpMode

• In the SDK, go to the TeamCode folder.
• Create a new Java class for your OpMode (the main program to control the robot):

1. Right-click on the opmode package in TeamCode.
2. Select New > Java Class, and name it MyFirstOpMode.

Step 4.2: Basic OpMode Structure

Every OpMode needs to extend the LinearOpMode or OpMode class. Here’s a basic structure:

package org.firstinspires.ftc.teamcode;

import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.hardware.DcMotor;

@com.qualcomm.robotcore.eventloop.opmode.TeleOp
public class MyFirstOpMode extends LinearOpMode {
    private DcMotor leftDrive;
    private DcMotor rightDrive;
    @Override
    public void runOpMode() {
        // Initialize motors
        leftDrive = hardwareMap.get(DcMotor.class, "left_drive");
        rightDrive = hardwareMap.get(DcMotor.class, "right_drive");
        // Wait for the game to start (driver presses PLAY)
        waitForStart();
        while (opModeIsActive()) {
            // Control motors using gamepad joysticks
            double drive = -gamepad1.left_stick_y;
            double turn = gamepad1.right_stick_x;
            double leftPower = drive + turn;
            double rightPower = drive - turn;
            leftDrive.setPower(leftPower);
            rightDrive.setPower(rightPower);
            // Send telemetry data to the Driver Station
            telemetry.addData("Left Power", leftPower);
            telemetry.addData("Right Power", rightPower);
            telemetry.update();
        }
    }
}

Step 4.3: Upload and Test

1. Connect your computer to the Control Hub via Wi-Fi.
2. In Android Studio, click the green “Run” button. This will compile your code and push it to the robot.
3. Open the FTC Driver Station app on your phone, select the MyFirstOpMode, and run it.

5. Understanding the Code

• hardwareMap: This connects the motor names in the code to the actual hardware configured on the robot.
• gamepad1.left_stick_y and gamepad1.right_stick_x: These capture input from the gamepad’s joysticks to control your robot.
• setPower(): This sets the speed for the motors. Positive values make the motor move forward, while negative values move it in reverse.

6. Expanding the Code

Step 6.1: Adding More Hardware

To control more hardware, like servos or sensors, follow the same process:

Servo armServo = hardwareMap.get(Servo.class, "arm_servo");
armServo.setPosition(1.0); // Set to a certain position

Step 6.2: Autonomous Mode

For autonomous programs, you can add time-based movement:

leftDrive.setPower(0.5);
rightDrive.setPower(0.5);
sleep(1000); // Move forward for 1 second

Next Steps

Once you’re comfortable with basic teleop (manual control) programming, you can start working on more advanced topics like:

• Autonomous programming: Program the robot to run pre-defined tasks without driver input.
• Sensors: Use REV sensors like IMUs, encoders, and color sensors for more precise control.

Good luck with your FTC season! The more you experiment with your robot, the better you’ll become at programming and controlling it.

Don’t forget to read

how to use encoders to program drivetrain and arm from next in the series: https://techiscoop.medium.com/robotics-coding-for-ftc-dc1458304688