<< Carrier board and Eagle library for Sharp GP2Y0D805 or GP2Y0D810 digital proximity sensors | Development of Festo - The Smart Bird >>

Using the HC-05 Bluetooth RS232 Serial module for cheap wireless communication between your PC and Arduino

Author: Filed under: Arduino

4 Apr 2011

I recently purchased the HC-05 RS232 serial bluetooth module from eBay. These modules sells from $10 to $20 including shipping. My plan was to use it as a economic wireless communication tool between PC and the Arduino board. The module has built-in Serial<-->Bluetooth protocol converter. Therefore it can be connected directly to Arduino serial pins without any ttl level translator chip and with a few external components. One thing to note though, the seller I purchased the module from on ebay had the wrong schematic posted on the listing which was meant for a older version of this module. So depending on which version you have, you will have slightly different pin connection for the AT command enable pin and led indicator pins. The major difference between the two version of the module is, the newer version works in both master and slave mode depending on how you set it up via AT commands and improved firmware. The specification of this module is as follows:

● Bluetooth protocol: Bluetooth Specification v2.0+EDR
● Frequency: 2.4GHz ISM band
● Modulation: GFSK(Gaussian Frequency Shift Keying)
● Emission power: ≤4dBm, Class 2
● Sensitivity: ≤-84dBm at 0.1% BER
● Speed: Asynchronous: 2.1Mbps(Max) / 160 kbps, Synchronous: 1Mbps/1Mbps
● Security: Authentication and encryption
● Profiles: Bluetooth serial port

Power supply: +3.3VDC 50mA
Working temperature: -20 ~ +75 Centigrade
Dimension: 26.9mm x 13mm x 2.2 mm

Here are the data sheet, example schematic for this module:

BC4_Bluetooth Module Datasheet.zip (1.12 mb)

The schematic I used to connect to arduino is as follows:

This can be used as a cheap way to talk to your Arduino wirelessly and debug your quad copter over serial port without using the relatively expensive XBee modules, even though you will not get as much range as the XBees.

Here is my version of the break out board.

Figure: Front side of the break out board.

Figure: Back side of the break out board.

Testing the module with MultiWii quad and configuration tool:

Tags: bluetooth, serial, rs232, arduino, hc05, hc-05

Experiment with ChipKIT Uno32 and Philips PCF8833 RGB 65K color lcd moduleUsing a philips PCF8833 color lcd module with arduino compatible ChipKIT Uno32 board.ChipKIT Uno32 and Philips PCF8833 color display module - Part 2Updated library to drive a philips pcf8833 color lcd module to display bitmap images.Arduino and Nokia 3310 display moduleThis is a experiment with arduino and nokia 3310 display module. I downloaded the library from http:...

Comments

Kai

9/1/2011 1:33:32 PM #

Hi Pial,

why did you use the 10 Ohms resistor (R5) in TX line?

Thank you
Kai

pial

9/2/2011 3:06:29 PM #

Hi Kai,
I used a 15 or 20 Ohms resister instead, because I didn't have any 10 Ohms in hand and it worked fine for me.

Thanks.

Kai

9/2/2011 3:15:06 PM #

Thanks for your reply. But my questions was, why to use a resistor in TX (!) line (regardless which size).
I know that using a voltage dividor in RX is needed to come get it from 5V down to 3.3V. But TX is 3.3V going to the Arduino...

Teejay

9/21/2011 6:52:43 AM #

Hi Pial,

I have the same bluetooth but the one i bought is the master not the slave one. Now i got this bluetooth working on uart interfaced to my microcontroller.

The problem is that when i want to change the name,password,baud etc. i cannot go to the AT command via serial com in pc

i already put the PIO11 in 3.3v or high level and still no response to any AT command. Everything is check even the connections, level converter.

Thanks
Teejay

pial

9/27/2011 11:07:01 PM #

Hi Teejay,
There are couple of firmware versions available for this module. You will need to check the data sheet or manual that is provided with your module. Your module could be programmed in a different way. Therefore it may not respond to AT commands exactly the way my modules did. Hope this helps.

assad

10/3/2011 4:00:22 AM #

is it possible to communicate 4 modules at a time

Anand Dhuru

11/28/2011 11:36:22 PM #

Hi, I have been trying to get an answer to this; hoping you can help!

I understand the ratio of resistors in the voltage divider for the Rx line. That is when you connect it to a TTL micro, right?

So, when one connects the module directly to a PC (real serial port, NOT USB-to-serial), wouldnt these have to be changed, to say 10K and 2.2K? Would like to be sure before I toast my module!

Regards,

Anand Dhuru

pial

11/29/2011 11:29:40 PM #

Hi Anand,
The voltage divider is used to lower the voltage to a tolarable limit of the module. When you are connecting it to the PC serial port, I believe the voltage will be more than 3.3v; which is the operating voltage of this module. So you will need a voltage divider to manage the voltage on tx/rx lines. Check this page to calculate your resistor values: http://en.wikipedia.org/wiki/Voltage_divider

Hope this helps.

Anand Dhuru

11/29/2011 11:34:05 PM #

Of course! I was being very dense. I now realize the module, when connected to a PC, will be thru'a level shifter (like a MAX232), so will not have to deal with non-TTL levels at its input. So, just a drop from 5 to 3.3 is what is required.

Thanks for the prompt response.

Regards,

Anand

Pooya

12/8/2011 1:31:32 AM #

Pial, do you know how I could set this module (HC-05) to low-power (energy-saving) mode? I'd really appreciate it if you could help me out.

Thanks
Pooya

Andre Matos

12/10/2011 7:21:34 PM #

Pial, I use same module, but I don't put resistor on tx / rx line, and my status led only work only on pin 24 (www.gemmarduino.com/PM-1/00100-002/datasheet.pdf page 4 ) , Bluetooth parity work ok on mac osx , what baud rate you are using ? I set mine as 115200 , configured with AT command with usb rs232 ttl ( wiki.openpilot.org/.../Serial+Bluetooth+Telemetry ) with pin 34 on 3v3 ( hight level ) .. but my setup don't work with my multiwii GUI ... start, connect to bluetooth , but don't star cycles, and sensors graph .. Thanks for any help and idea ... best regards, and great job, sorry bad english. Andre from Brazil

pial

12/10/2011 7:46:57 PM #

Hi Andre,
One major reason for the multiwii configuration to unable to communicate with the BT module is the BT stack installed on your mac/pc. I am not exactly sure about mac, but on my pc I had to install the toshiba bluetooth stack to make it work. Hope this helps.

Marcelo

12/23/2011 8:20:35 AM #

Hi Pail,

I'm trying to configure a BC417143BGQ(K121AY AND K119BL)

How may i know if i have HC05 or HC04/06?
www.hmangas.com/Electronica/Datasheets/Bluetooth%20Module/HC%20Serial%20Bluetooth%20Products%20201104.pdf

Can the Bluetooth module handle 5V from the Max232/PIC18?
or i should buy/build it?
http://www.sparkfun.com/products/8745

How did you install the bluetooth stack if your toshiba already has one?

Marcelo

12/23/2011 8:23:04 AM #

Thanks for any help.
best regards,
Marcelo

Marcelo

12/27/2011 5:52:31 AM #

Hello Pial,

I'm sorry i did a mistake and called you Pail instead of Your name in the earlier note.

Can you help me with the above

best regards,
Marcelo

pial

12/28/2011 2:35:49 PM #

Hi Marcelo,
I heard there are couple of variations of this module in the market. However, I was able to see only two of the variations. The picture posted here in this post with one of the chip marked as MX... is the HC-05 version, at least at the time I purchased the modules. The HC-04 module had a different chip (that was not marked as MX...). This module runs on 3.3V, so it will be a good idea to use a level converter/voltage devider between the rx/tx pins of the module and your microcontroller just to protect the module from over voltage damage. If you already have a toshiba laptop and it has the BT stack installed, you should be good to go. I had a dell and needed to install the toshiba BT stack on it.

I hope this helps.

Mehqui

1/12/2012 6:15:57 PM #

Hi Pial,

I'm doing a same project, but i need to integrate this module with Android plataform...

But at this moment, i had a lot difficult to communicate with bluetooth module... Apparently, my bluetooth module doesn't responding... I don't know why...

I'm trying to do a simple communication by UART interface on AT mode... i don't no why doesn't working...

Have some idea?
Maybe you can help me...

thank you

pial

1/15/2012 1:31:27 AM #

Guys, please follow this post on multwii, it has a lot of information on troubleshooting different variations of this bluetooth serial module:

www.multiwii.com/forum/viewtopic.php?f=6&t=133

Good luck!

Marcelo

1/15/2012 5:56:10 AM #

May be the solution is Max3232, works with 3V

Khan

2/23/2012 8:13:49 PM #

Hi Pial,

Please help me with the bluetooth module, i want to change the baud rate and the pairing info, i used a usb to ttl adapter, connected TX, RX of USB to ttl to RX, TX of Bluetooth Module respectively and applied 3.7V to the Bluetooth module(made sure that its not in paired mode, Led flashing) - The problem i have is, as soon as i open session - hyper-terminal or putty or any com tool, the BT module is contentiously sending non stop 'Y' kind of characters
"ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ"

This is what i bought off ebay : "NEW Serial Bluetooth RF Transceiver Module RS232 Master + backplane 4 pin TTL"
Item No: 110805911219

I tried going through all the google searches but no vail, please help. Thanks in advance, Khan

pial

2/24/2012 2:10:15 AM #

Hi Khan,
From your description it seems you do not have the correct baud rate set up in your terminal connection. Try changing the baud rate to match the one specified in your user manual and you should see correctly decoded characters on hyper terminal.

I hope this helps and good luck.

Khan

2/24/2012 6:51:10 AM #

Thanks Pial,

As per the product description provided by the seller the default baud is 9600, i will try all the available baud rates and will get back to you. Thanks again for the help.

>My other concern is (when connected to ttl adapter to modify the values), even if nothing is issued to the BT Module, its continuously sending data ...not sure y, do i have to pull up High - to the Key Pin ? and is there a way to identify what Module i am using, like HC04 or 05 or 06 .. ?

Mehqui

2/24/2012 7:50:44 AM #

I think your problem is with baud rate...
I had the same problem here... I changed the baud rate so many times to discover the correct baud rate of communication... When the baud rate is wrong, you will receive this kind of characters...

When i changed the baud rate to 115200, the communication works...

Khan

2/25/2012 2:44:59 PM #

Thank you Pial and Mehqui,

I am not sure what fixed it, but i was finally able to change the baud and pairing info.

I tried all the baudrates this time but nothing worked, all these time it would not even display those wierd characters and would never go into pairing, i tried 2 different rs232 to ttl boards nothing worked.

What my guess is, this time i soldered the tx,rx, gnd directly on the BTModule it self and used 9600 Baud, And was good to go.

So i am guessing a simple loose connection might have caused it, i didnt do any pullup or reset as mentioned at few places on googling..

By the way, i found this tool to be very helpful, you can type the AT+ command and then click send.. i was not able to do that on Hyperterminal

musicshield.googlecode.com/files/sscom32E.exe

Thanks guys for the help.
Good luck.

bambuko

3/18/2012 2:22:23 PM #

Thanks Pial !! - very useful, although might a bit too late for me?
Before I have found your blog I have connected my TX directly without voltage divider (at 5V) - I guess I have fried it? because now even with divider it doesn't work :-(
Or do you reckon it might have survived 5V and there is something else wrong with my setup?

bambuko

3/19/2012 11:00:51 AM #

Just a follow up to my yesterday's comment:
No I didn't fry it up!
After a bit of googling I have discovered that I needed MAX232 or MAX233 (I used the latter because it was easier to use) - my logger (which I have been trying to connect to BT module) was RS232 and the module requires TTL.
All is working perfect now - thank you.

Paola

4/26/2012 9:48:17 AM #

Deseo saber mi tiene UN MODULO BLUETOOTH HC04. si lo tiene cuanto vale?, cuanto se demora el envio.

Bluetooth Module

5/10/2012 11:06:36 PM #

I used such kind of module but their was a little shift in frequency band.. but i came to a conclusion that it was due to other connected devices. Because my other fellows also faced the same problem. This module worked well and its fast in data transfer.

Add comment