Recently I buy new HC-05 module ,but when i connect to arduino and i get garbage data on computer as well as phone .then i find that it work properly on 38400 baud rate ,so it has 38400 by default. In previous module the baud rate is 9600.so i get solution to change the baud rate.
Step 1: HARDWARE CONNECTION
I don't have key pin so i download data sheet.The key is 34 pin.i give 3.3v supply to it.
Then connect to arduino as shown in figure.
the logic level of Arduino is 5v but logic level of bluetooth module is 3.3 v.So you can also connect to it via resistance and form voltage devider.
Step 2: SOFTWARE SETUP
Open arduino and then you get a new page which has only empty setup and empty loop.Upload it to as it is.
Then open the serial monitor and set the baud rate to 38400 instead of 9600.
Also change the both No line ending to Both NL and CR
Step 3: AT COMMANDS
Then send AT serially and it will give the response OK
AT+UART? tell you the default baud rate
AT+UART=9600 set the baud rate to 9600.
AT+RESET reset and save changes.
According to data sheet when you connect 3.3v to key then LED on Module blink to 2 second interval.
But in my case it is not changing.so when you connect 3.3v to key it enter to AT command mode, LED blinking can be changed or not changed.