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

The HC-05 is a Bluetooth module designed and manufactured by Arduino to enable wireless communication between devices. It supports both master and slave modes, making it a versatile solution for a wide range of applications. The module is commonly used to establish communication between microcontrollers, such as Arduino boards, and Bluetooth-enabled devices like smartphones, tablets, or PCs.

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

The HC-05 module is a robust and reliable Bluetooth device with the following key specifications:

The HC-05 module has six pins, as described in the table below:

1. Power the Module: Connect the VCC pin to a 3.3V or 5V power source and the GND pin to the ground.
2. Connect TXD and RXD:
   • Connect the TXD pin of the HC-05 to the RX pin of the microcontroller.
   • Connect the RXD pin of the HC-05 to the TX pin of the microcontroller. Use a voltage divider if the microcontroller operates at 5V logic levels.
3. Enable Communication:
   • Leave the EN pin unconnected for normal operation (data mode).
   • Pull the EN pin high to enter command mode for configuration.
4. Pair the Module: Search for the HC-05 on your Bluetooth-enabled device. The default pairing code is 1234 or 0000.
5. Send and Receive Data: Use a serial communication library to send and receive data wirelessly.

• Voltage Levels: Ensure the RXD pin does not receive signals higher than 3.3V. Use a voltage divider if necessary.
• Baud Rate: The default baud rate is 9600 bps. Configure your microcontroller to match this rate.
• Command Mode: Use command mode to change settings like the module name, baud rate, or operating mode.
• Connection Status: Monitor the STATE pin to check if the module is connected to a device.

Below is an example of how to use the HC-05 module with an Arduino UNO to send and receive data:

#include <SoftwareSerial.h>

// Define RX and TX pins for SoftwareSerial
SoftwareSerial BTSerial(10, 11); // RX = Pin 10, TX = Pin 11

void setup() {
  Serial.begin(9600); // Start Serial Monitor at 9600 baud
  BTSerial.begin(9600); // Start Bluetooth communication at 9600 baud

  Serial.println("HC-05 Bluetooth Module Test");
  Serial.println("Send data from Serial Monitor to Bluetooth device.");
}

void loop() {
  // Check if data is available from Bluetooth
  if (BTSerial.available()) {
    char data = BTSerial.read(); // Read data from Bluetooth
    Serial.print("Received: ");
    Serial.println(data); // Print received data to Serial Monitor
  }

  // Check if data is available from Serial Monitor
  if (Serial.available()) {
    char data = Serial.read(); // Read data from Serial Monitor
    BTSerial.write(data); // Send data to Bluetooth device
    Serial.print("Sent: ");
    Serial.println(data); // Print sent data to Serial Monitor
  }
}

1. Module Not Powering On:

   • Ensure the VCC pin is connected to a 3.3V or 5V power source.
   • Check for loose connections or damaged wires.

2. Unable to Pair with Device:

   • Verify that the HC-05 is powered on and in range.
   • Ensure the correct pairing code (1234 or 0000) is used.
   • Check if the module is already paired with another device.

3. No Data Transmission:

   • Confirm that the TXD and RXD pins are correctly connected.
   • Match the baud rate of the HC-05 and the microcontroller.
   • Use a voltage divider if the microcontroller operates at 5V logic levels.

4. Cannot Enter Command Mode:

   • Pull the EN pin high before powering the module.
   • Use a serial terminal to send AT commands at the correct baud rate (default: 38400 bps).

Q: Can the HC-05 module communicate with another HC-05 module?
A: Yes, the HC-05 can communicate with another HC-05 module when one is set to master mode and the other to slave mode.

Q: What is the maximum range of the HC-05 module?
A: The HC-05 has a maximum range of up to 10 meters in an unobstructed environment.

Q: How do I change the module name or baud rate?
A: Enter command mode by pulling the EN pin high and use AT commands to configure the module. For example, use AT+NAME=NewName to change the name.

Q: Can the HC-05 work with 5V logic levels?
A: The HC-05 operates at 3.3V logic levels. Use a voltage divider on the RXD pin if connecting to a 5V microcontroller.

By following this documentation, you can effectively integrate the HC-05 Bluetooth module into your projects for seamless wireless communication.