How to Use HC-05 Bluetooth Module (6-pin male header): Examples, Pinouts, and Specs

The HC-05 Bluetooth module is a versatile and widely used component that enables wireless communication between devices. It is based on Bluetooth 2.0 technology and supports both master and slave modes, making it suitable for a variety of applications. The module features a 6-pin male header for easy integration with microcontrollers, such as Arduino, Raspberry Pi, and other embedded systems.

• Wireless data transmission between microcontrollers
• Remote control of robots, drones, and other devices
• Home automation systems
• Wireless sensor networks
• Serial communication replacement for wired connections

The HC-05 Bluetooth module is designed for reliable and efficient wireless communication. Below are its key technical details:

The HC-05 module has a 6-pin male header for easy connection. Below is the pinout:

The HC-05 Bluetooth module is straightforward to use in a circuit. Follow the steps below to integrate it into your project:

1. Wiring the Module:

   • Connect the VCC pin of the HC-05 to the 5V pin on the Arduino.
   • Connect the GND pin of the HC-05 to the GND pin on the Arduino.
   • Connect the TXD pin of the HC-05 to the RX (pin 0) of the Arduino.
   • Connect the RXD pin of the HC-05 to the TX (pin 1) of the Arduino. Use a voltage divider (e.g., 1kΩ and 2kΩ resistors) to step down the Arduino's 5V TX signal to 3.3V for the HC-05's RX pin.
   • Optionally, connect the EN/KEY pin to a digital pin on the Arduino for mode switching.

2. Uploading Code:

   • Disconnect the TXD and RXD pins while uploading code to the Arduino to avoid interference with the serial communication.

3. Example Code: Below is an example Arduino sketch to send and receive data via the HC-05 module:

   // Example code for HC-05 Bluetooth module with Arduino UNO
   // This code sends and receives data over Bluetooth.
   
   void setup() {
     Serial.begin(9600); // Initialize serial communication at 9600 baud
     Serial.println("HC-05 Bluetooth Module Initialized");
   }
   
   void loop() {
     // Check if data is available from the Bluetooth module
     if (Serial.available()) {
       char receivedChar = Serial.read(); // Read the incoming data
       Serial.print("Received: ");        // Print the received data
       Serial.println(receivedChar);
     }
   
     // Send data to the Bluetooth module
     Serial.println("Hello from Arduino!"); // Send a message
     delay(1000); // Wait for 1 second before sending the next message
   }
   

• Voltage Levels: The HC-05's RX pin operates at 3.3V logic. Use a voltage divider or level shifter when connecting to a 5V microcontroller.
• Mode Switching: To enter command mode, pull the EN/KEY pin HIGH before powering the module. In command mode, you can configure the module using AT commands.
• Baud Rate: Ensure the baud rate of the microcontroller matches the HC-05's default baud rate (9600 bps) or the configured baud rate.
• Interference: Avoid placing the module near sources of electromagnetic interference, such as motors or high-frequency circuits.

1. Module Not Responding:

   • Ensure the VCC and GND connections are secure.
   • Verify that the module is powered with the correct voltage (3.3V to 5V).
   • Check the baud rate settings in your code.

2. Unable to Pair with Device:

   • Ensure the module is in data mode (not command mode).
   • Check the Bluetooth name and PIN (default PIN is usually 1234 or 0000).

3. Data Transmission Issues:

   • Verify the TX and RX connections between the module and the microcontroller.
   • Use a voltage divider for the RX pin if the microcontroller operates at 5V logic.

4. STATE Pin Not Changing:

   • Ensure the module is properly paired with a Bluetooth device.
   • Check the wiring of the STATE pin.

Q1: Can the HC-05 module communicate with smartphones?
Yes, the HC-05 can communicate with smartphones that support Bluetooth 2.0 or higher. Use a terminal app to send and receive data.

Q2: How do I reset the HC-05 module?
To reset the module, disconnect and reconnect the power supply. Alternatively, use AT commands to restore factory settings.

Q3: Can I use the HC-05 module for audio transmission?
No, the HC-05 is designed for serial data communication and does not support audio transmission.

Q4: How do I change the module's name or PIN?
Enter command mode and use AT commands such as AT+NAME to change the name and AT+PSWD to change the PIN.

By following this documentation, you can effectively integrate and troubleshoot the HC-05 Bluetooth module in your projects.