HC-05 Bluetooth Module Master/Slave Serial Wireless Transceiver for Arduino/ESP32

Specifications:

• Protocol: Bluetooth v2.0+EDR
• Frequency: 2.4GHz ISM band
• Modulation: GFSK (Gaussian Frequency Shift Keying)
• Speed: Asynchronous: 2.1Mbps(Max) / 160 kbps; Synchronous: 1Mbps/1Mbps
• Power Supply: +3.6V to +6V DC
• Logic Level: 3.3V (Logic-Safe design)
• Range: ~30 Meters
• Modes: Master & Slave (Switchable via AT commands)

Key Applications

• Smartphone-Controlled Robotics: Build custom Android/iOS dashboards to drive motors.
• Remote Data Logging: Stream real-time sensor data to a PC without long cable runs.
• Wireless Debugging: Monitor serial output from a moving or enclosed robot.
• Industrial Automation: Wireless bridge for PLC-to-HMI communication.

Project Evolution

• The Journey: If you have mastered basic Serial (UART) communication using a USB-to-TTL converter, this module is your upgrade to the wireless world.
• The Upgrade: It unlocks the ability to control projects from across a room or place sensors in hard-to-reach locations where cabling is impossible.
• Effort Level: Intermediate. Requires basic knowledge of AT commands for configuration.

Virtual Technician & Wiring

• ⚠️ Safety First: The VCC pin takes 5V, but the RX pin requires 3.3V logic. Use a voltage divider or logic level converter when connecting to a 5V Arduino Uno.
• Pin Mappings:

1. VCC: 5V Input

2. GND: Ground

3. TXD: Connect to MCU RX

4. RXD: Connect to MCU TX (via 3.3V level shifter)

5. STATE: High when connected, Low when disconnected

6. EN/KEY: Pull High to enter AT Command Mode

Package Includes :

1 x HC-05 Bluetooth Module Master/Slave Serial Wireless Transceiver for Arduino/ESP32

Frequently Asked Questions (FAQ)

     1. What is the default pairing code?
          Usually 1234 or 0000.

      2. Can this act as a Master?
           Yes, the HC-05 can both initiate and receive connections.

      3. How do I change the Bluetooth name? 
          Use AT Command AT+NAME=YourName in Command Mode.

      4. What is the default baud rate?
           9600 bps for communication, 38400 for AT mode.

      5. Can I connect this to my iPhone?
          No, the HC-05 (BT 2.0) is generally not compatible with iOS. Use HM-10                    (BLE) instead.

      6. Why is the LED blinking fast? 
           It is searching for a pair.

      7. Why is the LED blinking slowly (every 2s)?
           It is in AT Command Mode.

      8. Is it 5V tolerant?
           Power is 5V, but data pins are 3.3V.

      9. Can I use it with ESP32? 
           Yes, ESP32 is 3.3V native, so no level shifter is needed.

      10. What is the maximum range?
             Approximately 10 meters in open air.

      11. How many devices can connect at once?
               It supports point-to-point communication (one-to-one).

      12. Can I use it to transfer large files? 
               No, it is designed for low-speed serial data.

      13. How do I enter AT mode?
              Hold the button while powering on or pull the EN pin High.

      14. My laptop sees it but won't pair?
             Ensure your Bluetooth drivers are updated and the module is not
             already connected to another device.

      15. Does it support audio?
             No, this is for SPP (Serial) data only.

      16. What is the current consumption?
           ~30-40mA during pairing and ~8mA when connected.

      17. Can I change the PIN code?
             Yes, use AT+PSWD="XXXX".

      18. Does it work with Raspberry Pi? 
             Yes, via the GPIO UART pins.

      19. What is the difference between HC-05 and HC-06?
              HC-05 is Master/Slave; HC-06 is Slave only.

       20. Is the antenna built-in?
               Yes, it uses an onboard PCB trace antenna.