Understanding the HC-06 and HC-05 Bluetooth Modules

The HC-06 and HC-05 are Bluetooth modules widely used in microcontroller projects for enabling wireless communication between devices. These modules are particularly popular in Arduino-based projects due to their simplicity and effectiveness. They allow serial communication over Bluetooth, making them ideal for projects ranging from home automation to robotics. While both modules serve similar purposes, they differ significantly in functionality, configuration, and applications. Below, we’ll dive deep into their features, differences, and step-by-step setup with Arduino Uno.

HC-05 Bluetooth Module

Functionality

The HC-05 module operates as both a Master and Slave device. This means it can initiate communication with other Bluetooth devices (Master mode) or respond to commands from a Master device (Slave mode). This dual functionality makes it versatile and suitable for various applications.

Applications

The HC-05 is perfect for projects that require bidirectional communication. Examples include:

Smartphone-controlled robots
Wireless data transfer between devices
Device-to-device communication setups

Configuration

The HC-05 can be configured into either Master or Slave mode using AT commands. It comes with a default baud rate of 9600, which can be adjusted based on project requirements. The extensive configurability of the HC-05 makes it adaptable to complex setups.

Compatibility

The HC-05 works seamlessly with popular microcontrollers such as:

Arduino (all models)
ESP32
Raspberry Pi

HC-06 Bluetooth Module

Functionality

Unlike the HC-05, the HC-06 operates solely as a Slave device. It can only respond to requests from a paired Master device, making it less flexible but easier to use.

Applications

The HC-06 is ideal for simple, straightforward projects where the module only needs to receive commands. Examples include:

Turning on a light or motor via a smartphone
Basic wireless data logging

Configuration

The HC-06 has limited configuration options compared to the HC-05. Its default baud rate is 9600 and cannot be changed. However, this simplicity makes it beginner-friendly.

Compatibility

The HC-06 is compatible with:

Arduino microcontrollers
Other basic microcontroller setups

Key Differences between HC-05 and HC-06

Feature	HC-05	HC-06
Operating Mode	Master and Slave	Slave only
Configuration Options	Extensive (via AT commands)	Limited
Applications	Versatile, multi-device communication	Simple, master-controlled projects
Default Baud Rate	9600 (adjustable)	9600 (fixed)

Setting Up HC-05 or HC-06 with Arduino Uno

Both modules can be connected to an Arduino Uno in a similar manner. The steps below outline the hardware and software setup process.

Required Components

Arduino Uno
HC-05 or HC-06 Bluetooth Module
Jumper Wires

Wiring Diagram

Bluetooth Module Pin	Arduino Pin
VCC	5V
GND	GND
TXD	RX (Pin 0) with a voltage divider
RXD	TX (Pin 1)

Note: The RX pin on the Bluetooth module operates at 3.3V. To prevent damage, use a voltage divider between the Arduino’s TX (5V) and the module’s RX.

Arduino Code Example

The following code tests the Bluetooth connection by reading and printing data received via Bluetooth:

void setup() {
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  if (Serial.available()) {
    char data = Serial.read();  // Read incoming Bluetooth data
    Serial.print("Received: ");
    Serial.println(data);       // Display data in Serial Monitor
  }
}

Upload Instructions

Disconnect the RX (Pin 0) and TX (Pin 1) wires from the Bluetooth module.
Upload the code to the Arduino Uno.
Reconnect the Bluetooth module after the upload completes.

Testing the Connection

Pair your smartphone with the Bluetooth module.
Use a Bluetooth terminal app to send commands.
Check the Serial Monitor in the Arduino IDE for received data.

Default Pairing PIN: Typically 1234 or 0000.

Configuring HC-05 with AT Commands

Entering AT Command Mode

Connect the EN pin on the HC-05 to 3.3V.
Open the Serial Monitor in the Arduino IDE.
Type AT commands to configure the module.

Common AT Commands

AT – Test communication (responds with OK)
AT+ROLE=1 – Set to Master mode
AT+ROLE=0 – Set to Slave mode
AT+UART=9600,1,0 – Set baud rate to 9600

Tips for Choosing the Right Module

Use HC-05 for complex setups requiring bidirectional communication or Master functionality.
Use HC-06 for simple projects where the module acts only as a receiver.
Ensure proper wiring and voltage levels to avoid damaging components.