Modify The HC-05 Bluetooth Module Defaults Using AT Commands

Picture of Modify The HC-05 Bluetooth Module Defaults Using AT Commands
September 4, 2013: Featured on
September 1, 2013: Featured on


In this guide, I will explain how to use Arduino to change the settings of the ubiquitous HC-05 Bluetooth module using the AT command set. The HC-05 comes with a rich set of AT commands to perform various tasks such as changing the module's default settings including changing the pass code, the device name, and the baud rate. But the process of switching the HC-05 into AT command mode for first time users of the module is not straight forward and the docs takes short cuts. There are a couple of ways to do this. I have picked the one I think is the easiest  I will do my best to illustrate the process in simple to follow steps. You can find the full set of AT commands in the attached datasheet.


The HC-05 Bluetooth module and its siblings are by far the most popular and inexpensive Bluetooth modules used for RF communications by microcontroller hackers. It costs less than $10 on ebay and it's easy to implement. I have published two guides based on the HC-05 Bluetooth module.  The first guide explains how to use the HC-05 with the Arduino. The second is an Android app that simplifies controlling Arduino from your smart phone over Bluetooth using the HC-05. In both cases, the default settings for the HC-05 were fine. 

In the process of using the HC-05 for a project, I ran into a situation where I needed to change the defaults for the module. For example, the default baud rate on the HC-05 is 9600. That's slow for high-speed transmission. The HC-05 can go as high as 1382400 baud rate according to the HC-05 reference. Also, the HC-05 has a default device name of HC-05. Having two or more of those devices in the same area can be confusing. You can use an AT command to change the device name. Also, the pin code default is 1234. You may wish to change that for some projects to ensure basic security.

After spending some time searching the web I realized many people are having a hard time changing the default settings for the HC-05. Switching the HC-05 from data transmission mode to configuration mode, to send AT commands to the HC-05, involves a few wiring and software acrobatics.  Add to the mix all the variations of the HC Bluetooth module family and the various vendor settings and you get the picture. 

This guide only covers the HC-05 module with the breakout board. 


The HC-05 is a 3.3V system but the breakout board offers current limiting resistors for some protection. While it's not advisable to keep the HC-05 connected to the 5V Arduino Uno pins, for this short exercise I decided to skip the voltage dividers which I use to drop 5V to 3.3V. I advise you to use voltage dividers whenever you connect the HC-05 pins to  5V pins such as the Arduino Uno. If you skip the voltage divider, do so at your own risk.
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I have tried your method of putting the HC-05 module AT command mode with no luck. However, I have discovered that there are some models with a small button that you can hold down while it is powering up that will put it into AT command mode.

can u tell me what is the procedure for it.,

i have that small button type HC-05

can u tell me what is the procedure for it.,

i have that small button type HC-05

can u tell me what is the procedure for it.,

i have that small button type HC-05

stsoky2 months ago


I try everything, but still does not work.

1. problem

I have not blinking led, I do not how, but nothing blinkig when I connect arduino and HC-05. I checked few times conneciton.

2. problem

After some time i get this silly result when I try AT command in Serial Port:
Try to solve this with different baudrate (try on Win8 and Linux Mint)

2.1 ( BTSerial.begin(9600) ) whatever i send to arduino on serial I get same command,

Tx = AT; Rx=AT ..

2.2 (BTSerial.begin(38400) ) if I send command "AT" I get "xxø", for different command different simbols.

2.3 (BTSerial.begin(1382400)) for "AT" got nothing.

3. Also I try case with 3.3V on Key, but unfortunetly that also did not work.

Some idea or solution?

JDEAN73 stsoky6 days ago

Exact same problem! Any luck with solving this stsoky? Or anyone else?

me also exact same problem, any one rectified it?

abhi9nav11 days ago

how to change password

AT+HELP will list your command set

abhi9nav11 days ago

how to change password

abhi9nav11 days ago

how to change password

abhi9nav11 days ago

how to change password

abhi9nav11 days ago


i am using hc-05 for my project,

how to change its password ;

please tell me in simple way,

abhi9nav11 days ago


i am using hc-05 for my project,

how to change its password ;

please tell me in simple way,

loiphin15 days ago

After messing around with it for a couple of hours I finally got it to work!! I did a bit differently....

I used Windows 8 plus Arduino 1.05 on a Arduino Uno R3

My particular HC-05 was defaulting to 38400 BAUD. Therefore I changed the Terminal emulation speed within Arduino Serial Monitor to 38400 + Both NL + CR on the bottom right.

Then changed the program to also be 38400 (ie, Serial.begin(38400);)

Looks like the speed mismatch wasn't allowing it to work properly.

Also to get it into command mode, I followed the original instructions by applying the Vcc to the HC-05 after booting the Arduino Uno. You will know its in command mode when the LED blinks slowly on and off, around 2 seconds between on/off.

Once the HC-05 is in command mode you can then reboot the Arduino and mess withe the code to your hearts content, to get it to work. As long as you dont remove the power the HC-05 will stay in command mode (slow blink on the LED).

Hope it helps:)


Stouf_1 month ago

Thanks for the command ref PDF, it's very usefull !

rfuentes5 made it!1 month ago

SUCCESS! thx, definitelly this method will work, no matter what, with the correct module, take a look if your module's HC-05 or HC-06


Hi rfuentes5. I tried step by step, the LED is blinking every 2s (I found it longer than that) but in serial monitor whatever I typed it doesn't respone. I bought the HC-05 from amazon

I even changed BTSerial.begin(9600); but still no respone. Do you have any idea?

vomov4 months ago

I'm using your code, which gives me the 'OK' after I send 'AT', and I have even succeeded in renaming it. However, if I do this: AT+NAME=THINGY, it gives it the name of "=THINGY". Aside from this, no other commands seem to do anything. Any advice?

rwaliya vomov2 months ago

for name, check you have put only one '=' sign.

and for other changes the AT commands refer this link :

vomov rwaliya2 months ago

I already figured it out; it turns out there are different ways of working with the AT commands, one of which (cheap Chinese knockoff) only uses a tiny subset of commands and does not require the '=' sign. I now also have another bluetooth module, which works as it should.

Also, thanks for the link: there was a command I was curious about that followed from the text in the pdf.

jiddoabdo3 months ago
lafiona3 months ago

I have try use AT command for getting the RSSI value.

I'm trying the command "at+inq\n\r" (from datasheet)
but i only get OK and i can't understand that,

can you help me to find where the mistake is?

agentnoise4 months ago

I am unable to get this to work at all. I have gone over these steps 40 million times, any ideas why it might not be working? I have tried Wenabe's method too, and it will not work.

I know you have to first right the key pin high and then connect the 5v but even doing that wont work.

I figured it out. Mine has a button that you have to hold down while it boots in order to right the pin high.

bstott made it!4 months ago

Thanks for the education.

WhizzWr5 months ago

One IMPORTANT thing, Newline feed (\n) and Carriage return (\r) are needed on every AT command entered. So if you're using Arduino's serial monitor make sure you select "Both NL and CR" on the dropdown.

shanX WhizzWr4 months ago


accio5 months ago

With Mega, Mega 2560 and Leonardo not all the pins can be used to connect with the HC-05 via SoftwareSerial Library (used in the sketch).


Once I found the right pins, I was able to use the HC_05.ino as is. Very useful!

samuelee5 months ago

Thanks for your instructions !

Unfortunately, after I've connected the circuit, there was no reaction when I applied AT command. Please kindly give your advice !

Details of my equipment :

  1. Arduino UNO R3

2. BT-Board V1.4

samuelee samuelee5 months ago

The LED on the BT board blinked rapidly (not 2-second blinking) throughout the experiment.

_MeRKeZ_6 months ago

That's a great work. Thanks Mr.

CATFARTS26 months ago

Have spent hours, but still get no response to AT commands. My HC-05 is purported to run at 9600 out of box, but no dice setting BTSerial.begin to either 9600 or original 38400 setting. Wiring and order of operations is correct and AT mode blinking is there - I even tried Wenabe's method, but that just put me into data mode (fast blinking) and didnt go back to AT mode. Have tried every line end option but there is absolutely no reply. When I send any text to UNO, only the rx LED lights up and there is no activity in tx LED.

Any help is appreciated.

Goines6 months ago

Thanks a lot, I've managed to get my HC-05 fully loaded up the way I'd like it to be!

I do have one problem though; no devices I have (Windows machines, or phone) will automatically reconnect via Bluetooth when the power is cycled to the HC-05. Have you had problems with this, or do you know how to get previous pairs to re-establish themselves?

Thanks again

Excellent guide, really helpful and well written. Thanks for submitting it.

kf5qgf6 months ago

Just a note, I couldn't get this to work on an Arduino Leonardo, but it does work great on the Arduino Uno.

funky8111 months ago
I've tried your code and schema here. But somehow it doesnt work. I already make sure my wiring correct. I'm using UNO and HC05 (bought from aliexpress).
What I have already tried is that I connect my UNO directly to PC.
Then I open serial monitor @ 9600. But still I dont get any responses from UNO.

wenabe funky817 months ago
Hi funky81,
See my reply to Luke534. It might help.
techbitar (author)  funky8111 months ago
It's not enough to have the same wiring. The order of events outlined in "Step 3: Steps To Switch The HC-05 Into Command Mod" is also important.
jornfranke10 months ago

I cannot get it to work. The led blinks off and on every 2 seconds and I see the "Enter Serial Commands: " in the Serial Monitor, but I do not receive an answer when I enter AT.

I am also struggling to connect to it via Linux in normal mode. "hcitool scan" shows me the device, but I cannot connect.

Can you help me?

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