💻Programming Code

🎯 Lesson Objective

In this lesson, students will learn:

• How to program the Voice Control Robot
• How the ESP32 receives commands from a smartphone through Bluetooth
• How voice commands are converted into control signals
• How the ESP32 controls the motors using the L298N motor driver
• How the robot moves according to voice instructions

By the end of this lesson, students will be able to upload the program and control the robot using voice commands from a smartphone.

1️⃣ Complete Copy-Paste Code

Students can copy and paste the following code directly into Arduino IDE.

#include "BluetoothSerial.h"

BluetoothSerial SerialBT;

int motor1A = 26;
int motor1B = 27;
int motor2A = 14;
int motor2B = 12;

String voiceCommand;

void setup()
{
Serial.begin(9600);
SerialBT.begin("ESP32_Voice_Robot");

pinMode(motor1A, OUTPUT);
pinMode(motor1B, OUTPUT);
pinMode(motor2A, OUTPUT);
pinMode(motor2B, OUTPUT);

Serial.println("Voice Control Robot Ready");
}

void loop()
{
if(SerialBT.available())
{
voiceCommand = SerialBT.readStringUntil('\n');
voiceCommand.trim();

Serial.println(voiceCommand);

if(voiceCommand == "forward")
{
moveForward();
}

else if(voiceCommand == "backward")
{
moveBackward();
}

else if(voiceCommand == "left")
{
turnLeft();
}

else if(voiceCommand == "right")
{
turnRight();
}

else if(voiceCommand == "stop")
{
stopRobot();
}
}
}

void moveForward()
{
digitalWrite(motor1A, HIGH);
digitalWrite(motor1B, LOW);

digitalWrite(motor2A, HIGH);
digitalWrite(motor2B, LOW);
}

void moveBackward()
{
digitalWrite(motor1A, LOW);
digitalWrite(motor1B, HIGH);

digitalWrite(motor2A, LOW);
digitalWrite(motor2B, HIGH);
}

void turnLeft()
{
digitalWrite(motor1A, LOW);
digitalWrite(motor1B, HIGH);

digitalWrite(motor2A, HIGH);
digitalWrite(motor2B, LOW);
}

void turnRight()
{
digitalWrite(motor1A, HIGH);
digitalWrite(motor1B, LOW);

digitalWrite(motor2A, LOW);
digitalWrite(motor2B, HIGH);
}

void stopRobot()
{
digitalWrite(motor1A, LOW);
digitalWrite(motor1B, LOW);

digitalWrite(motor2A, LOW);
digitalWrite(motor2B, LOW);
}

2️⃣ Program Logic

The robot follows this behavior:

1️⃣ The user speaks a command into the smartphone.
2️⃣ The smartphone converts the voice into text.
3️⃣ The app sends the text command through Bluetooth.
4️⃣ The ESP32 receives the command.
5️⃣ The program checks the command and moves the robot accordingly.

Example commands:

3️⃣ Bluetooth Library

The program uses the BluetoothSerial library.

This library allows the ESP32 to communicate with Bluetooth devices such as smartphones.

4️⃣ Creating a Bluetooth Object

This creates a Bluetooth communication object.

It will be used to send and receive Bluetooth data.

5️⃣ Starting Bluetooth Communication

Inside the setup function:

This line starts Bluetooth communication.

The name ESP32_Voice_Robot will appear in the smartphone Bluetooth device list.

Students will connect their phone to this device.

6️⃣ Motor Pin Declaration

These pins control the motor driver inputs.

Motor mapping:

• motor1A & motor1B → Left motor
• motor2A & motor2B → Right motor

7️⃣ Reading Voice Commands

Inside the loop function:

This reads the text command sent from the smartphone.

The command is stored in the voiceCommand variable.

The trim() function removes extra spaces.

8️⃣ Command Processing

The program checks which command was received.

Example:

If the command is forward, the robot moves forward.

Similar conditions are used for other commands.

9️⃣ Movement Functions

Each robot movement is controlled using a function.

Forward Movement

Both motors rotate forward.

Backward Movement

Both motors rotate backward.

Left Turn

Left motor reverses and right motor moves forward.

Right Turn

Right motor reverses and left motor moves forward.

Stop Robot

All motors stop.

1️⃣0️⃣ Final Working Process

The Voice Control Robot works as follows:

1️⃣ The user speaks a command into the smartphone.
2️⃣ The smartphone converts the voice into text.
3️⃣ The command is sent to the ESP32 through Bluetooth.
4️⃣ The ESP32 reads the command.
5️⃣ The ESP32 controls the motors based on the command.
6️⃣ The robot moves according to the voice instruction.

1️⃣1️⃣ Common Mistakes

Students may encounter the following issues:

⚠ Phone not connecting → check Bluetooth pairing
⚠ Robot not moving → verify motor driver wiring
⚠ Voice command not recognized → check the mobile app configuration
⚠ Robot moving wrong direction → swap motor wires

Always verify the wiring and Bluetooth connection first.

🚀 What Happens Next

Now that the Voice Control Robot program is uploaded, the final step is to test the robot and explore improvements.