ex04

Exercise 4

This exercise demonstrates how to use a Bluetooth module (HC-05) with an Arduino to send and receive data wirelessly. The Arduino will echo back any received data via Bluetooth and print it to the Serial Monitor.

Tools Required

• Arduino Uno (or any compatible board)
• HC-05 or HC-06 Bluetooth module
• Jumper wires
• Two resistors (1kΩ and 2kΩ) for a voltage divider
• Power source (e.g., USB cable or 9V battery)
• Serial Bluetooth Terminal app (available for iOS/Android)

Schematic Description

HC-05 Pin	Arduino Pin
VCC	5V
GND	GND
TXD	RX (Pin 10 via voltage divider)
RXD	TX (Pin 11)

Ensure the voltage divider is used for the RXD pin of the HC-05 to step down the Arduino's 5V TX signal to 3.3V.

Code

#include <SoftwareSerial.h>

// Define RX and TX pins for the Software Serial port
SoftwareSerial BTSerial(10, 11); // RX | TX

void setup()
{
    // Initialise hardware serial port (for monitoring)
    Serial.begin(9600);
    // Initialise Bluetooth serial port
    BTSerial.begin(9600);

    Serial.println("Bluetooth Module is ready!");
}

void loop()
{
    // Check if data is available on Bluetooth
    if (BTSerial.available())
    {
        char incomingData = BTSerial.read(); // Read the data
        Serial.print("Received via Bluetooth: ");
        Serial.println(incomingData); // Print on Serial Monitor

        // Echo the received data back to the Bluetooth device
        BTSerial.write(incomingData);
    }

    // Check if data is available on Serial Monitor
    if (Serial.available())
    {
        char outgoingData = Serial.read(); // Read the data
        BTSerial.write(outgoingData);      // Send it to the Bluetooth device
        Serial.print("Sent via Bluetooth: ");
        Serial.println(outgoingData);
    }
}

Exercise Steps

1. Connect the Hardware:
   • Build the circuit as per the schematic diagram.
   • Ensure the HC-05's LED is blinking, indicating it is in pairing mode.
2. Pair the Bluetooth Module:
   • On your phone, search for nearby Bluetooth devices.
   • Pair with the HC-05 using the default password (1234 or 0000).
3. Install a Bluetooth Terminal App:
   • Download a serial Bluetooth terminal app (e.g., "Serial Bluetooth Terminal") on your phone.
4. Test Communication:
   • Open the app, connect to the HC-05, and type a message.
   • Observe the message being echoed back on the app and printed on the Arduino Serial Monitor.

When you send a character or string from the Bluetooth terminal app, it will appear in the Arduino Serial Monitor. Similarly, typing in the Serial Monitor will send data to the Bluetooth terminal app.