HC-05 pinout, specifications, datasheet and HC05 Arduino connection

HC-05 Bluetooth module is a Bluetooth to serial converter that connects microcontrollers (like Arduino) to other Bluetooth enabled devices. HC-05 pinout and specifications are given b

HC-05 Pinout with Description:

HC-05 Pinout
PIN NO.Pin NamePin Description
1.KEY/EnThis pin is used to bring the Bluetooth module in AT commands mode. By default, this pin operates in data mode. The Key/EN pin should be high to operate Bluetooth in command mode. In HC-05, the default baud speed in command mode is 38400bps and 9600 in data mode.
2.VCCUsed to power the Bluetooth module. Give 5V / 3.3 V to this Pin.
3.GNDThe ground pin of the module
4.TXDConnect this pin with the RXD pin of the Microcontroller. This pin transmits Serial data (wireless signals received by the Bluetooth module are converted by module and transmitted out serially on this pin)
5.RXDConnect this pin to the TXD pin of the Microcontroller. The HC-05 Bluetooth module receives the data from this pin and then transmits it wirelessly.
6.STATEIt is used to check if the module is connected or not. It acts as a status indicator.
HC-05 Description

HC-05 Specifications

HC-05 Specifications
HC-05 Specifications

**Image Source: Electrosome

  • Bluetooth protocol: Bluetooth Specification v2.0+EDR (Enhanced Data Rate)
  • Frequency: 2.4GHz ISM band
  • Modulation: GFSK (Gaussian Frequency Shift Keying)
  • Emission power: ≤4dBm, Class 2
  • Sensitivity: ≤-84dBm at 0.1% BER
  • Speed: Asynchronous communication: 2.1Mbps (Max) / 160 kbps, Synchronous communication: 1Mbps/1Mbps
  • Security: Authentication and encryption
  • Profiles: Bluetooth serial port
  • Supply Voltage: +3.3V to 6.0 V
  • Supply Current: 30mA
  • Working temperature: -20 ~ +75Centigrade
  • Dimension: 26.9mm x 13mm x 2.2 mm
  • HC-05 Bluetooth module follows the IEEE 802.15.1 standardized protocol, through which one can build a wireless Personal Area Network (PAN). It uses frequency-hopping spread spectrum (FHSS) radio technology to send data over the air.

HC-05 Bluetooth module datasheet:

Download the full datasheet from this link: HC-05 Datasheet

Introduction to HC-05 Bluetooth Module

The HC-05 is very easy to use Bluetooth to serial converter. HC-05 connects microcontrollers (like Arduino) to other Bluetooth enabled devices. This allows the devices to communicate wirelessly with each other.

HC-05 Bluetooth Module
HC-05 Bluetooth Module

HC-05 is a Bluetooth SPP (Serial Port Protocol) module designed for wireless communication. It can also be operated as a master or slave configuration.

Working of HC-05 Bluetooth Module:

The HC-05 Bluetooth Module can be used in two modes of operation: Command Mode and Data Mode.

Command Mode:

In Command Mode, we can communicate with the Bluetooth module through AT Commands to configure various settings and parameters of the Module. This includes the firmware information, changing Baud Rate, changing module name, etc. We can also use it to set HC-05 as a master or slave. To select either of the modes, we need to activate the Command Mode and sent the correct AT Commands. Baud rate is 38400bps in command mode.

Data Mode:

In this mode, the module is used for communicating with other Bluetooth devices i.e. data transfer happens in this mode. Exchange of data between devices. Baud rate is 9600bps in data mode.

HC-05 Breakout Board Pinout:

HC-05 Breakout board pinout
HC-05 Breakout board pinout
PIN NamePinTypeDescription
GND13,21,22VSSGround Pot
3.3 VCC123.3VIntegrated 3.3V supply with On-chip linear regulator output within 3.15-3.3V
AIO09Bi-directionalProgrammable input/output line
AIO110Bi-directionalProgrammable input/output line
AIO023Bi-directional RX ENProgrammable input/output line, control output for LNA
AIO124Bi-directional TX ENProgrammable input/output line, control output for PA
PIO225Bi-directionalProgrammable input/output line
PIO326Bi-directionalProgrammable input/output line
PIO427Bi-directionalProgrammable input/output line
PIO528Bi-directionalProgrammable input/output line
PIO629Bi-directionalProgrammable input/output line
PIO730Bi-directionalProgrammable input/output line
PIN0831Bi-directionalProgrammable input/output line
PIO932Bi-directionalProgrammable input/output line
PIO1033Bi-directionalProgrammable input/output line
PIO1134Bi-directionalProgrammable input/output line
RESET11CMOS input with weak internal pull-upReset of low. Input debounced must be low for >5MS to cause a reset
UART_RTS4CMOS output, tri-stable with weak internal pull-upUART request to send, active low
UART_CTS3CMOS input with weak internal pull-downUART clear to send, active low
UART_RX2CMOS input with weak internal pull-downUART Data input
UART_TX1CMOS output, tri-stable with weak internal pull-upUART Data output
SPI_MOSI17CMOS input with weak internal pull-downThe Serial peripheral interface data input
SPI_CSB16CMOS input with weak internal pull-upChip select for the serial peripheral interface, active low
SPI_CLK19CMOS input with weak internal pull-downThe Serial peripheral interface clock
SPI_MISO18CMOS input with weak internal pull-downThe Serial peripheral interface data output
PCM_CLK5Bi-directionalThe Synchronous PCM data clock
PCM_OUT6CMOS outputThe Synchronous PCM data output
PCM_IN7CMOS inputThe Synchronous PCM data input
PCM_SYNC8Bi-directionalThe Synchronous PCM data strobe

HC-05 Arduino Connections:

HC-05 connection with Arduino
HC-05 connection with Arduino
  • Connect and a LED to an Arduino board with the help of jumper wires.
  • Connect the Bluetooth module (HC-05) to the Arduino with the help of jumper wires. Except for the first and the last pin, all other pins need to be connected to the Arduino.
  • Ground of HC-05 to Ground of Arduino.
  • Power of HC-05 to 3.3V of Arduino.
  • Tx of HC-05 to Rx of Arduino.
  • Rx of HC-05 to Tx of Arduino.

 ** Full tutorial here: Arduino Remote controlled LED using HC-05

Applications of HC-05 Bluetooth module:

  • Computer and peripheral devices
  • GPS receiver
  • Industrial control
  • MCU projects

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