Bluetooth Module HC-05

Bluetooth Module HC-05 module is an easy to use Bluetooth SPP (Serial Port Protocol) module,designed for transparent wireless serial connection setup.The HC-05 Bluetooth Module can be used in a Master or Slave configuration, making it a great solution for wireless communication.This serial port bluetooth module is fully qualified Bluetooth V2.0+EDR (Enhanced Data Rate)3Mbps Modulation with complete 2.4GHz radio transceiver and baseband. It uses CSR Bluecore 04‐External single chip Rluetooth system with CMOS technology and with AFH (Adaptive Frequency Hopping Feature).

The Bluetooth module HC-05 is a MASTER/SLAVE module.By default the factory setting is SLAVE.The Role of the module (Master or Slave) can be configured only by AT COMMANDS.The slave modules cannot initiate a connection to another Bluetooth device, but can accept connections.Master module can initiate a connection to other devices.The user can use it simply for a serial port replacement to establish connection between MCU and GPS, PC to your embedded project, etc.

Bluetooth Module HC-05

Bluetooth Module HC-05 Pinout

Bluetooth Module HC-05 Pinout

Pin Description

Bluetooth serial modules allow all serial enabled devices to communicate with each other using Bluetooth.

It has 6 pins,

1.  Key/EN: It is used to bring Bluetooth module in AT commands mode. If Key/EN pin is set to high, then this module will work in command mode. Otherwise by default it is in data mode. The default baud rate of HC-05 in command mode is 38400 bps and 9600 bps in data mode.

HC-05 module has two modes,

→ Data mode: Exchange of data between devices.

→ Command mode: It uses AT commands which are used to change setting of HC-05. To send these commands to module serial (USART) port is used.

2.  VCC: Connect 5 V or 3.3 V to this Pin.

3.  GND: Ground Pin of module.

4.  TXD: Transmit Serial data (wirelessly received data by Bluetooth module transmitted out serially on TXD pin)

5.  RXD: Receive data serially (received data will be transmitted wirelessly by Bluetooth module).

6.  State: It tells whether module is connected or not.

HC-05 Module Information

  • HC-05 has red LED which indicates connection status, whether the Bluetooth is connected or not. Before connecting to HC-05 module this red LED blinks continuously in a periodic manner. When it gets connected to any other Bluetooth device, its blinking slows down to two seconds.
  • This module works on 3.3 V. We can connect 5V supply voltage as well since the module has on board 5 to 3.3 V regulator.
  • As HC-05 Bluetooth module has 3.3 V level for RX/TX and microcontroller can detect 3.3 V level, so no need to shift transmit level of HC-05 module. But we need to shift the transmit voltage level from microcontroller to RX of HC-05 module.

Hardware Features

Typical ‐80dBm sensitivity.
Up to +4dBm RF transmit power.
3.3 to 5 V I/O.
PIO (Programmable Input/Output) control.
UART interface with programmable baud rate.
With integrated antenna.
With edge connector.

Software Features

Slave default Baud rate: 9600, Data bits:8, Stop bit:1,Parity:No parity.
Auto‐connect to the last device on power as default
Permit pairing device to connect as default.
Auto‐pairing PIN CODE :”1234” as default.

Command Mode

When we want to change settings of HC-05 Bluetooth module like change password for connection, baud rate, Bluetooth device’s name etc.
To do this, HC-05 has AT commands.
To use HC-05 Bluetooth module in AT command mode, connect “Key” pin to High (VCC).
Default Baud rate of HC-05 in command mode is 38400 bps.
Following are ome AT command generally used to change setting of Bluetooth module.
To send these commands, we have to connect HC-05 Bluetooth module to the PC via serial to USB converter and transmit these command through serial terminal of PC.

Command Description Response
AT Checking communication OK
AT+PSWD=XXXX Set Password e.g. AT+PSWD=4567 OK
AT+NAME=XXXX Set Bluetooth Device Name e.g. AT+NAME=MyHC-05 OK
AT+UART=Baud rate, stop bit, parity bit Change Baud rate e.g. AT+UART=9600,1,0 OK
AT+VERSION? Respond version no. of Bluetooth module +Version: XX OK e.g. +Version: 2.0 20130107 OK
AT+ORGL Send detail of setting done by manufacturer Parameters: device type, module mode, serial parameter, passkey,etc.

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