AT Command mode of HC-05

HC-05 Bluetooth Module support both Master and Slave roles. We can set it in AT Command mode. There are a number of variant of HC-05, and different ways to enter AT Command mode. For my samples, there is a button on the lower-right, above EN pin. It's used to enter AT Command mode when power-on.

This video show how to connect PC to HC-05, via FTDI USB-to-Serial adapter, power-on HC-05 in AT Command mode, and enter AT Command using Arduino Serial Monitor to check setting of HC-05.


Please notice both FTDI USB-to-Serial adapter and HC-05 have to work on the same voltage, both 3.3V or both 5V.

- Connect FTDI and HC-05
FTDI Tx - HC-05 Rx
FTDI Rx - HC-05 Tx
FTDI GND - HC-05 GND
(no power apply to HC-05 now)

- Connect FTDI to PC using USB cable.
- You can check the COM port connect to FTDI in Deviec Manager.
- Start Arduino IDE, and run Tools > Serial Monitor.
- Set baud rate 38400 and select "both NL & CR".

- Press the on-board button of HC-05.
- Apply power to HC-05.
- The on-board LED of HC-05 will blink slowly.
- Now it's in AT Command mode.

- You can type AT command in Arduino Serial Monitor to check or set the setting of HC-05.

Some useful command:
AT : return OK if connect correctly.
AT+NAME : get/set name of the device. Nothing return in my sample.
AT+ADDR : display default address
AT+VERSION : display firmware version
AT+UART : get/set serial communication setting; such as baud, number of stop bit, and parity.
AT+ROLE: get/see role of bt module(1=master/0=slave)
AT+RESET : Reset and exit AT mode
AT+ORGL : Restore factory settings
AT+PSWD: get/set default PIN

reference:
- iteadstudio: Serial Port Bluetooth Module (Master/Slave) : HC-05
- HC-03/05 Embedded Bluetooth Serial Communication Module
AT command set