HC-05 is a Bluetooth module. It can operate as either a slave device or a master device. Default set as a slave, but can be re-configured as a master via AT commands (Module initiallized as Data mode by default). To go to AT command mode press the push button on the module. AT Command mode is use to change the system parameters.

• Wiring (only need 4 wires):
  • RX to RXD
  • TX to TXD
  • GND to GND
  • 3.6V to 6V
• Logic Power: 3.3V (connect to 5v devices via logic level converter)

Specifications

• Bluetooth v2.0
• 2.4GHz
• Baud rate:
  • 9600
  • 19200
  • 38400 [default]
  • 57600
  • 115200
  • 230400
  • 460800
• Speed:
  • Asynchronous: 2.1Mbps(Max) / 160 kbps
  • Synchronous: 1Mbps/1Mbps
• Power supply: 3.6V to 6V DC (Logic is 3.3v)
• Passkey: 1234

References

• http://www.instructables.com/id/AT-command-mode-of-HC-05-Bluetooth-module/
• http://www.instructables.com/id/Communication-Bluetooth-Module-With-HC-05-HC-06/
• http://www.martyncurrey.com/arduino-with-hc-05-bluetooth-module-in-slave-mode/