How to Use HC-05: Examples, Pinouts, and Specs

The HC-05 is a Bluetooth module designed for wireless communication. Manufactured by AZ-Delivery, this module is widely used to establish a connection between microcontrollers and other Bluetooth-enabled devices. It supports both Master and Slave modes, making it versatile for various applications.

• Wireless Data Transmission: Ideal for sending and receiving data wirelessly between microcontrollers and smartphones, tablets, or PCs.
• Remote Control Systems: Used in projects where remote control of devices is required, such as home automation systems.
• Robotics: Enables wireless control and communication in robotic systems.
• IoT Projects: Facilitates wireless communication in Internet of Things (IoT) applications.

1. Power Supply: Connect the VCC pin to a 3.3V or 5V power supply and the GND pin to the ground.
2. Data Communication: Connect the TXD pin of the HC-05 to the RX pin of the microcontroller and the RXD pin of the HC-05 to the TX pin of the microcontroller.
3. Enable Pin: The EN pin can be connected to a digital pin of the microcontroller to enable or disable the module programmatically.
4. Status LED: The LED pin can be used to monitor the status of the module.

• Voltage Levels: Ensure that the voltage levels are compatible. The HC-05 operates at 3.3V logic levels, so use a voltage divider or level shifter if interfacing with a 5V microcontroller.
• Baud Rate: The default baud rate of the HC-05 is 9600. Ensure that the microcontroller's serial communication is set to the same baud rate.
• Pairing: When pairing with another Bluetooth device, the default PIN code is usually "1234" or "0000".

#include <SoftwareSerial.h>

// Create a software serial port on pins 10 (RX) and 11 (TX)
SoftwareSerial BTSerial(10, 11);

void setup() {
  // Start the hardware serial port
  Serial.begin(9600);
  // Start the software serial port
  BTSerial.begin(9600);
  Serial.println("Enter AT commands:");
}

void loop() {
  // Read from the hardware serial port and send to the software serial port
  if (Serial.available()) {
    BTSerial.write(Serial.read());
  }
  // Read from the software serial port and send to the hardware serial port
  if (BTSerial.available()) {
    Serial.write(BTSerial.read());
  }
}

1. Module Not Powering On:

   • Solution: Check the power supply connections. Ensure that VCC is connected to a 3.3V or 5V source and GND is connected to ground.

2. No Data Transmission:

   • Solution: Verify the TXD and RXD connections. Ensure that the TXD pin of the HC-05 is connected to the RX pin of the microcontroller and vice versa.

3. Unable to Pair with Bluetooth Device:

   • Solution: Ensure that the HC-05 is in pairing mode (LED blinking rapidly). Check the default PIN code (usually "1234" or "0000").

4. Incorrect Baud Rate:

   • Solution: Ensure that both the HC-05 and the microcontroller are set to the same baud rate (default is 9600).

• Q: Can the HC-05 module be used with a 5V microcontroller?

  • A: Yes, but ensure to use a voltage divider or level shifter for the RXD pin to avoid damage.

• Q: How do I change the baud rate of the HC-05?

  • A: You can change the baud rate using AT commands. For example, send AT+UART=115200,0,0 to set the baud rate to 115200.

• Q: What is the range of the HC-05 module?

  • A: The HC-05 module has a range of up to 10 meters in open space.

• Q: Can the HC-05 module be used for audio transmission?

  • A: No, the HC-05 is designed for data transmission and does not support audio transmission.

This documentation provides a comprehensive guide to using the HC-05 Bluetooth module, ensuring both beginners and experienced users can effectively integrate it into their projects.