Course: 09. Wireless Communication

Introduction

Introduction to Wireless Communication in Robotics

As robots become more advanced, the ability to communicate without wires becomes essential. Wireless communication allows robots to be controlled remotely, share data, and even work together in teams. In this section, we’ll explore what wireless communication is and how it helps us build smarter and more interactive robots.

Select activity What & Why
🤖 What is Wireless Communication?

Wireless communication is the transfer of data between two or more devices without physical connection using radio waves, infrared, or Bluetooth.

It allows us to send commands from a remote control, smartphone, or another device to the robot.

📡 Why Do Robots Need Wireless Communication?

To be controlled remotely from a phone, tablet, or computer

To operate in places where direct contact is not possible (e.g., search & rescue, drones)

To work in groups or swarms, sharing data wirelessly

🔌 Types of Wireless Communication in Robotics

Technology	Range	Common Uses
Bluetooth	10–30 meters	Mobile app control, short-range data transfer
Wi-Fi	Up to 100 meters	Internet-connected robots, home automation
Infrared (IR)	Line of sight, short range	Remote controls, TV robots
RF Modules	Up to 500 meters (varies)	Long-range remote control, wireless sensors

📘 What We’ll Focus On

In this course, we’ll primarily work with Bluetooth communication using modules like HC-05 or HC-06. These are beginner-friendly, affordable, and perfect for controlling your robot using a phone app.

By the end of this section, you should be able to:

Understand the need for wireless communication in robotics
Identify different wireless technologies and their uses
Prepare to use Bluetooth in your own robot projects

Bluetooth Modules

Getting to Know Bluetooth Modules (HC-05, HC-06)

Bluetooth modules like HC-05 and HC-06 allow your Arduino-based robots to wirelessly receive commands from a mobile device. Understanding how these modules work is key to building wirelessly controlled robots.

Select activity What
🔷 What is the HC-05/HC-06 Module?

Both are popular Bluetooth modules used in hobby electronics.

HC-05 can work as both Master and Slave.

HC-06 works only in Slave mode (for receiving commands).

📦 Pin Description

Pin	Description
VCC	Connect to 5V (power)
GND	Ground
TXD	Transmit Data (connects to Arduino RX)
RXD	Receive Data (connects to Arduino TX via voltage divider)
STATE / EN / KEY	Used in advanced configuration (not required for basic use)

🔌 Basic Wiring with Arduino

HC-05 VCC → Arduino 5V
HC-05 GND → Arduino GND
HC-05 TXD → Arduino RX (pin 0)
HC-05 RXD → Arduino TX (pin 1) via 1K–2K voltage divider

⚠️ Important Note:

The HC-05 RXD pin is not 5V tolerant, so it's recommended to use a voltage divider when connecting to Arduino TX to avoid damaging the module.

📶 Pairing the Module

Turn on Bluetooth on your phone.
Scan for devices — look for “HC-05” or “HC-06”.
Default pairing code is usually 1234 or 0000.
Once paired, your phone can communicate with the robot using apps like MIT App Inventor or Bluetooth Terminal.

✅ What You’ve Learned

The difference between HC-05 and HC-06
Pin functions and connection to Arduino
How to wire and pair your Bluetooth module

Setting Up

Setting Up Arduino with Bluetooth

Now that you’ve learned the basics of Bluetooth and the HC-05 module, it’s time to set up the Arduino to communicate wirelessly. This section covers how to wire the module, switch between modes, and test communication using simple code.

Select activity Connections
🔌 Connecting HC-05 to Arduino

HC-05 VCC → Arduino 5V

HC-05 GND → Arduino GND

HC-05 TX → Arduino RX (Pin 0)

HC-05 RX → Arduino TX (Pin 1) (use a voltage divider to step down 5V to 3.3V)

📡 Understanding Serial Communication

Bluetooth modules like HC-05 use UART serial communication. It is important to wire TX of one device to RX of the other and vice versa.

TX: Transmit line of Bluetooth

RX: Receive line of Bluetooth

Make sure baud rate matches in code (default is 9600)

⚙️ Upload vs. Communicate Mode

When the HC-05 is connected to RX/TX pins of the Arduino (pins 0 and 1), the Arduino may face issues uploading code. Here's what to do:

During Upload: Disconnect HC-05

After Upload: Reconnect HC-05 to use Serial

This is because the same pins are used for USB upload and Serial communication. If you want to avoid this, consider using SoftwareSerial (we’ll cover that later).
Select activity Sample Code
💻 Sample Code – Send and Receive Serial Data

Upload this code to Arduino to read Bluetooth data and respond via Serial Monitor.

void setup() { Serial.begin(9600); Serial.println("Bluetooth ready. Waiting for data..."); } void loop() { if (Serial.available()) { char data = Serial.read(); Serial.print("Received: "); Serial.println(data); } }

🔍 Testing the Communication

Upload the above code to Arduino

Open the Serial Monitor and set baud to 9600

Connect your phone to HC-05 using a Bluetooth terminal app

Send characters from your phone and see them printed in Serial Monitor

✅ What You Learned

How to wire and connect HC-05 Bluetooth module to Arduino

Difference between upload and communication modes

Tested two-way communication using a terminal app

This setup is the heart of Bluetooth-based projects. In the next section, we’ll build a full robot using this wireless communication.

MIT App Inventor

Controlling a Robot via Mobile App (MIT App Inventor)

Now that your Bluetooth module is connected, it's time to build a simple mobile app that sends commands to your robot. We will use MIT App Inventor, a beginner-friendly, drag-and-drop platform for making Android apps.

Select activity What
📱 What is MIT App Inventor?

A free online tool that lets you build apps by dragging and connecting blocks.

Great for beginners and works directly from your browser.

Apps can be tested live using the MIT AI2 Companion app.
Select activity Start
🌐 Getting Started

Go to MIT App Inventor

Sign in with your Google account.

Create a new project and name it something like BluetoothBot.

📲 Designing the App Interface

Add Buttons for robot controls: Forward, Backward, Left, Right, Stop

Add a ListPicker to choose the Bluetooth device

Use a Label to show connection status

🔧 App Blocks Logic

Each button will send a letter or number via Bluetooth to the robot. For example:

Forward → Send "F"

Backward → Send "B"

Left → Send "L"

Right → Send "R"

Stop → Send "S"

Use the BluetoothClient block to send these characters when the button is clicked.
Select activity Code
🤖 Arduino Code to Receive Commands

char command; void setup() { Serial.begin(9600); pinMode(5, OUTPUT); // Left Motor pinMode(6, OUTPUT); // Right Motor } void loop() { if (Serial.available()) { command = Serial.read(); if (command == 'F') { // Move forward digitalWrite(5, HIGH); digitalWrite(6, HIGH); } else if (command == 'S') { // Stop digitalWrite(5, LOW); digitalWrite(6, LOW); } // Add more conditions for B, L, R } }

🛠️ Testing and Troubleshooting

Make sure your phone is paired with the HC-05 or HC-06.

Install the MIT AI2 Companion app to test your interface.

Ensure the baud rate in Serial.begin() matches the module (usually 9600).

✅ What You’ve Learned

How to build a simple Bluetooth control app using MIT App Inventor

How to send commands from phone to Arduino

How to receive and use Bluetooth commands in Arduino code

Project

Mini Project – Bluetooth Controlled Robot

Now that you’ve learned to control your Arduino using Bluetooth and an Android app, it’s time to bring everything together into a mini project: a robot that you can steer using your mobile phone!

Select activity You Will Need
📦 What You’ll Need

Arduino Uno or Nano

HC-05 or HC-06 Bluetooth module

Motor driver module (like L298N)

Two DC motors with wheels

Robot chassis

Battery pack (7.4V Li-ion or AA x 4)

Jumper wires

Android phone with MIT AI2 Companion app

🔗 Wiring the Circuit

Connect the motors to the motor driver (IN1, IN2, IN3, IN4)

Connect ENA and ENB of the motor driver to PWM pins on Arduino (e.g., 5 and 6)

Connect HC-05 TX to Arduino RX, and RX to TX via voltage divider

Connect power and GND properly to motor driver and Bluetooth module

🔌 Suggested Pin Connections

Component	Connected To
Motor IN1	Pin 7 (Arduino)
Motor IN2	Pin 8
Motor IN3	Pin 9
Motor IN4	Pin 10
ENA	Pin 5 (PWM)
ENB	Pin 6 (PWM)
HC-05 TX	Pin 0 (RX)
HC-05 RX	Pin 1 (TX via 1k-2k voltage divider)

💻 Sample Arduino Code

char command;

void setup() {
  Serial.begin(9600);
  pinMode(5, OUTPUT); // ENA
  pinMode(6, OUTPUT); // ENB
  pinMode(7, OUTPUT); // IN1
  pinMode(8, OUTPUT); // IN2
  pinMode(9, OUTPUT); // IN3
  pinMode(10, OUTPUT); // IN4
}

void loop() {
  if (Serial.available()) {
    command = Serial.read();

    if (command == 'F') {
      digitalWrite(7, HIGH); digitalWrite(8, LOW); // Left motor forward
      digitalWrite(9, HIGH); digitalWrite(10, LOW); // Right motor forward
    } else if (command == 'B') {
      digitalWrite(7, LOW); digitalWrite(8, HIGH);
      digitalWrite(9, LOW); digitalWrite(10, HIGH);
    } else if (command == 'L') {
      digitalWrite(7, LOW); digitalWrite(8, HIGH);
      digitalWrite(9, HIGH); digitalWrite(10, LOW);
    } else if (command == 'R') {
      digitalWrite(7, HIGH); digitalWrite(8, LOW);
      digitalWrite(9, LOW); digitalWrite(10, HIGH);
    } else if (command == 'S') {
      digitalWrite(7, LOW); digitalWrite(8, LOW);
      digitalWrite(9, LOW); digitalWrite(10, LOW);
    }
  }
}

🎮 Using the Mobile App

Connect to the Bluetooth module via the ListPicker
Tap the direction buttons to control your robot
Observe how your robot responds to your commands

🚧 Debugging Tips

Check Bluetooth pairing and serial baud rate
Ensure motors are connected correctly (swap IN1/IN2 or IN3/IN4 if needed)
Test commands via Serial Monitor first

🏁 What You Achieved

Assembled a basic robot using Arduino and Bluetooth
Built a mobile app to send directional commands
Tested and debugged a working wireless control system

This mini project is a huge step toward building more advanced wireless robots and automation systems. You’ve now combined hardware, software, and mobile interaction into one seamless project!

Wireless Robot in Action

Project: Wireless Robot in Action

Time to bring everything together! In this final section, you’ll assemble your full Bluetooth-controlled robot, test it with the app, and troubleshoot any issues that arise during communication or movement.

Select activity Circuit Setup
🔗 Final Circuit Setup and Wiring

Make sure your connections are secure and complete. Here's a checklist:

Motor Driver: L298N module wired to both motors

Arduino: Connected to L298N and Bluetooth module

Bluetooth Module: HC-05 connected via TX/RX (use voltage divider on RX)

Power: External battery pack connected to motor driver (and optionally Arduino)

Note: Double-check ground connections – all devices should share a common GND.
Select activity Testing & Debugging
📱 Testing App Control with Robot

Turn on the robot and connect your phone to the HC-05 module.

Open the Bluetooth control app (e.g., MIT App Inventor app you built).

Test each button: Forward, Backward, Left, Right, and Stop.

Observe how the robot reacts – motors should respond immediately.

🛠 Debugging Communication Issues

If the robot doesn’t respond as expected, check the following:

Baud Rate Mismatch: Ensure Arduino code uses the correct serial speed (usually 9600).

RX/TX Swapped: TX from Bluetooth should go to RX on Arduino, and vice versa.

App Command Mismatch: Confirm that the app is sending the correct characters expected by your Arduino code.

Power Issues: Motors may not respond if power is low or unstable.

✅ What You Achieved

Completed a functional wireless robot

Tested Bluetooth commands from a mobile app

Debugged real-time robot communication

This project marks a big leap in your robotics journey. You’ve now built and controlled a robot remotely — a skill that opens up tons of creative possibilities ahead!

Tips, Safety, and Troubleshooting

Before wrapping up your wireless robot project, it’s important to follow good practices for safe usage, effective communication, and smooth troubleshooting. This section highlights useful tips that will help you avoid common mistakes and keep your robot running reliably.

Select activity Bluetooth Modules
🔒 Safe Handling of Bluetooth Modules

Voltage Limits: Most Bluetooth modules (like HC-05) operate at 3.3V on RX. If using with a 5V Arduino, use a voltage divider or level shifter.

Heat Awareness: Modules may heat up during extended use. Avoid touching them while powered for long periods.

Antenna Care: Avoid bending or crushing the onboard antenna to maintain strong signal quality.
Select activity Common Errors & Improving
🛠 Common Errors and How to Fix Them

Robot Not Responding: Check Bluetooth pairing, ensure power supply is stable, and verify command strings from the app.

Upload Error: Disconnect the Bluetooth module during code upload to Arduino (TX/RX interfere with uploading).

App Controls Wrong Action: Review your code to ensure each character sent from the app matches the right function in Arduino logic.

Random Movements: This could be caused by poor signal or incorrect command interpretation. Add Serial Monitor print statements for debugging.

📶 Improving Range and Reliability

Line of Sight: Keep your phone in direct line of sight with the robot for best Bluetooth performance.

Distance: HC-05 typically works well up to 10 meters in open space. Avoid walls or metal obstacles.

Shielding: Place the Bluetooth module away from motor wires and power sources to reduce electrical interference.

App Lag: Use lightweight commands (single characters) for faster transmission and less processing delay.

By following these tips and safety checks, you'll create a more robust and enjoyable robotics experience. You’re now fully ready to build wireless robots with confidence!

Summary and Quiz

Congratulations! You have now completed the course on Wireless Communication with Arduino. You've explored the world of Bluetooth modules like HC-05, learned how to pair and communicate with mobile apps, and built your own Bluetooth-controlled robot. These foundational skills are essential for creating interactive and remotely operated robotic systems.

Now, it's time to test your understanding. Let’s take a quiz to review everything you’ve learned and see how confidently you can apply wireless control in your own projects.

Select activity Quiz

Quiz

Section outline

Introduction to Wireless Communication in Robotics

🤖 What is Wireless Communication?

📡 Why Do Robots Need Wireless Communication?

🔌 Types of Wireless Communication in Robotics

📘 What We’ll Focus On

Getting to Know Bluetooth Modules (HC-05, HC-06)

🔷 What is the HC-05/HC-06 Module?

📦 Pin Description

🔌 Basic Wiring with Arduino

⚠️ Important Note:

📶 Pairing the Module

✅ What You’ve Learned

Setting Up Arduino with Bluetooth

🔌 Connecting HC-05 to Arduino

📡 Understanding Serial Communication

⚙️ Upload vs. Communicate Mode

💻 Sample Code – Send and Receive Serial Data

🔍 Testing the Communication

✅ What You Learned

Controlling a Robot via Mobile App (MIT App Inventor)

📱 What is MIT App Inventor?

🌐 Getting Started

📲 Designing the App Interface

🔧 App Blocks Logic

🤖 Arduino Code to Receive Commands

🛠️ Testing and Troubleshooting

✅ What You’ve Learned

Mini Project – Bluetooth Controlled Robot

📦 What You’ll Need

🔗 Wiring the Circuit

🔌 Suggested Pin Connections

💻 Sample Arduino Code

🎮 Using the Mobile App

🚧 Debugging Tips

🏁 What You Achieved

Project: Wireless Robot in Action

🔗 Final Circuit Setup and Wiring

📱 Testing App Control with Robot

🛠 Debugging Communication Issues

✅ What You Achieved

Tips, Safety, and Troubleshooting

🔒 Safe Handling of Bluetooth Modules

🛠 Common Errors and How to Fix Them

📶 Improving Range and Reliability