HC-05 Wireless Bluetooth Module

HC-05 is a Bluetooth module which is designed for wireless communication. This module can be used in a master or slave configuration.

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 38400bps and 9600 in data mode.

HC-05 module has two modes,

          1.  Data mode: Exchange of data between devices.

          2.  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 3.3V. 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 3.3V 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.
• The data transfer rate of HC-05 module can vary up to 1Mbps is in the range of 10 meters. 

Specification of HC-05 Bluetooth Module

• Bluetooth version: 2.0 + EDR (Enhanced Data Rate)
• Frequency: 2.4 GHz ISM band
• Modulation: GFSK (Gaussian Frequency Shift Keying)
• Transmit power: Class 2 (up to 4 dBm)
• Sensitivity: -80 dBm typical
• Range: approximately 10 meters (or 33 feet) in open air
• Profiles supported: SPP (Serial Port Profile), HID (Human Interface Device) and others
• Operating voltage: 3.3V to 5V DC
• Operating current: less than 50mA
• Standby current: less than 2.5mA
• Sleep current: less than 1mA
• Interface: UART (Universal Asynchronous Receiver/Transmitter)
• Baud rates: 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, 230400, and 460800
• Operating temperature: -20°C to 75°C (-4°F to 167°F)