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HC 05 Bluetooth Module pin out, applications.

HC-05 - Bluetooth Module


Pin Configuration

Pin Number ; 1
Pin Name ; Enable / Key
Description ; This pin is used to toggle between Data Mode (set low) and AT command mode 
                        (set high). By default it is in Data mode

Pin Number ; 2
Pin NameVcc
Description Powers the module. Connect to +5V Supply voltage

Pin Number ; 3
Pin Name ; Ground
DescriptionGround pin of module, connect to system ground.

Pin Number ; 4
Pin NameTX – Transmitter
Description ; Transmits Serial Data. Everything received via Bluetooth will be given out by 
                          this pin as serial data.

Pin Number ; 5
Pin Name ;  RX – Receiver
Description ;  Receive Serial Data. Every serial data given to this pin will be broadcasted via                                         Bluetooth

Pin Number ; 6
Pin Name ;  State
Description ;  The state pin is connected to on board LED, it can be used as a feedback to 
                           check if  Bluetooth is working properly.

Pin Number ; 7
Pin Name ;  LED
Description ;  Indicates the status of Module
                        Blink once in 2 sec: Module has entered Command Mode
                        Repeated Blinking: Waiting for connection in Data Mode
                        Blink twice in 1 sec: Connection successful in Data Mode

Pin Number ; 8
Pin NameButton
DescriptionUsed to control the Key/Enable pin to toggle between Data and command Mode

HC-05 Default Settings

  • Default Bluetooth Name: “HC-05”
  • Default Password: 1234 or 0000
  • Default Communication: Slave
  • Default Mode: Data Mode
  • Data Mode Baud Rate: 9600, 8, N, 1
  • Command Mode Baud Rate: 38400, 8, N, 1
  • Default firmware: LINVOR

HC-05 Technical Specifications

  • Serial Bluetooth module for Arduino and other microcontrollers
  • Operating Voltage: 4V to 6V (Typically +5V)
  • Operating Current: 30mA
  • Range: <100m
  • Works with Serial communication (USART) and TTL compatible
  • Follows IEEE 802.15.1 standardized protocol
  • Uses Frequency-Hopping Spread spectrum (FHSS)
  • Can operate in Master, Slave or Master/Slave mode
  • Can be easily interfaced with Laptop or Mobile phones with Bluetooth
  • Supported baud rate: 9600,19200,38400,57600,115200,230400,460800.

HC-05 Equivalent Bluetooth Module


Other Bluetooth Modules

HC-04, HC-06, HM-11, ESP32, CSR8645

Where to use HC-05 Bluetooth module

The HC-05 is a very cool module which can add two-way (full-duplex) wireless functionality to your projects. You can use this module to communicate between two microcontrollers like Arduino or communicate with any device with Bluetooth functionality like a Phone or Laptop. There are many android applications that are already available which makes this process a lot easier. The module communicates with the help of USART at 9600 baud rate hence it is easy to interface with any microcontroller that supports USART. We can also configure the default values of the module by using the command mode. So if you looking for a Wireless module that could transfer data from your computer or mobile phone to microcontroller or vice versa then this module might be the right choice for you. However do not expect this module to transfer multimedia like photos or songs; you might have to look into the CSR8645 module for that.

How to Use the HC-05 Bluetooth module

The HC-05 has two operating modes, one is the Data mode in which it can send and receive data from other Bluetooth devices and the other is the AT Command mode where the default device settings can be changed. We can operate the device in either of these two modes by using the key pin as explained in the pin description.

It is very easy to pair the HC-05 module with microcontrollers because it operates using the Serial Port Protocol (SPP). Simply power the module with +5V and connect the Rx pin of the module to the Tx of MCU and Tx pin of module to Rx of MCU as shown in the figure below


During power up the key pin can be grounded to enter into Command mode, if left free it will by default enter into the data mode. As soon as the module is powered you should be able to discover the Bluetooth device as “HC-05” then connect with it using the default password 1234 and start communicating with it. The name password and other default parameters can be changed by entering into the


1. Wireless communication between two microcontrollers

2. Communicate with Laptop, Desktops and mobile phones

3. Data Logging application

4. Consumer applications

5. Wireless Robots

6. Home Automation

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