Complete ROS 4WD Robot Guide

From Ubuntu Installation to Keyboard & Xbox Controller Teleoperation

This is a crystal-clear, beginner-safe, end-to-end robotics guide. Follow every step in order and you will build a fully drivable ROS robot using a Raspberry Pi.

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ROADMAP — WHAT YOU WILL BUILD

1. Install Ubuntu 20.04 on Raspberry Pi
2. Install & verify ROS Noetic
3. Wire & test motors (without ROS)
4. Create ROS motor driver node
5. Keyboard teleoperation
6. Xbox wireless controller teleoperation

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DAY 1 — Ubuntu & ROS Noetic Setup

1. Enable SSH

sudo systemctl enable ssh
sudo systemctl start ssh
sudo systemctl status ssh

2. Update System

sudo apt update
sudo apt upgrade -y

3. Install ROS Noetic

sudo apt install software-properties-common -y
sudo add-apt-repository universe
sudo apt update
sudo apt install ros-noetic-desktop-full -y

4. Setup ROS Environment

echo "source /opt/ros/noetic/setup.bash" >> ~/.bashrc
source ~/.bashrc

5. Verify ROS

roscore

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DAY 2 — Motor Wiring & Standalone Testing (NO ROS)

GPIO Mapping (Example: L298N)

• ENA → GPIO18
• IN1 → GPIO17
• IN2 → GPIO27
• ENB → GPIO13
• IN3 → GPIO22
• IN4 → GPIO23

Motor Test Script (motor_test.py)

#!/usr/bin/env python3
import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)

ENA, IN1, IN2 = 18, 17, 27
ENB, IN3, IN4 = 13, 22, 23

GPIO.setup([ENA, IN1, IN2, ENB, IN3, IN4], GPIO.OUT)

print("Moving Forward")
GPIO.output(IN1, GPIO.HIGH)
GPIO.output(IN2, GPIO.LOW)
GPIO.output(IN3, GPIO.HIGH)
GPIO.output(IN4, GPIO.LOW)

time.sleep(2)
GPIO.cleanup()

Run Test

python3 motor_test.py

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DAY 3 — ROS Motor Driver Node

Create ROS Package

cd ~/catkin_ws/src
catkin_create_pkg my_4wd_robot rospy geometry_msgs
cd ~/catkin_ws
catkin_make
source devel/setup.bash

Motor Driver Node (motor_driver_node.py)

#!/usr/bin/env python3
import rospy
from geometry_msgs.msg import Twist
import RPi.GPIO as GPIO

ENA, IN1, IN2 = 18, 17, 27
ENB, IN3, IN4 = 13, 22, 23

GPIO.setmode(GPIO.BCM)
GPIO.setup([ENA, IN1, IN2, ENB, IN3, IN4], GPIO.OUT)

def cmd_vel_callback(msg):
    lin = msg.linear.x
    ang = msg.angular.z

    if lin > 0:
        GPIO.output(IN1, GPIO.HIGH)
        GPIO.output(IN2, GPIO.LOW)
        GPIO.output(IN3, GPIO.HIGH)
        GPIO.output(IN4, GPIO.LOW)
    elif lin < 0:
        GPIO.output(IN1, GPIO.LOW)
        GPIO.output(IN2, GPIO.HIGH)
        GPIO.output(IN3, GPIO.LOW)
        GPIO.output(IN4, GPIO.HIGH)
    elif ang > 0:
        GPIO.output(IN1, GPIO.LOW)
        GPIO.output(IN2, GPIO.HIGH)
        GPIO.output(IN3, GPIO.HIGH)
        GPIO.output(IN4, GPIO.LOW)
    elif ang < 0:
        GPIO.output(IN1, GPIO.HIGH)
        GPIO.output(IN2, GPIO.LOW)
        GPIO.output(IN3, GPIO.LOW)
        GPIO.output(IN4, GPIO.HIGH)
    else:
        GPIO.output(IN1, GPIO.LOW)
        GPIO.output(IN2, GPIO.LOW)
        GPIO.output(IN3, GPIO.LOW)
        GPIO.output(IN4, GPIO.LOW)

rospy.init_node("motor_driver")
rospy.Subscriber("/cmd_vel", Twist, cmd_vel_callback)
rospy.spin()

Make Executable

chmod +x motor_driver_node.py

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DAY 4 — Keyboard Teleoperation

Install Teleop Package

sudo apt install ros-noetic-teleop-twist-keyboard -y

Run Nodes (Correct Order)

# Terminal 1
roscore

# Terminal 2
rosrun my_4wd_robot motor_driver_node.py

# Terminal 3
rosrun teleop_twist_keyboard teleop_twist_keyboard.py

Keyboard Controls

• W → Forward
• S → Backward
• A → Left
• D → Right
• X → Stop

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DAY 5 — Xbox Wireless Controller (Bluetooth)

Pair Controller

bluetoothctl

power on
agent on
default-agent
scan on

pair XX:XX:XX:XX:XX:XX
trust XX:XX:XX:XX:XX:XX
connect XX:XX:XX:XX:XX:XX
quit

Verify Controller

ls /dev/input/js0
jstest /dev/input/js0

Headless pygame Fix

import os
os.environ["SDL_VIDEODRIVER"] = "dummy"

Run Xbox Teleop

rosrun xbox_teleop xbox_teleop_node.py

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FINAL RESULT

• ROS fully working
• Motors respond correctly
• Keyboard control stable
• Xbox wireless control smooth

The robot now drives like butter.

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NEXT UPGRADES

• Deadman safety button
• Speed modes
• Launch files
• Auto-start on boot

This guide documents a real debugging journey — not a copy-paste tutorial.