OldMan and Bluetooth

Introduction: OldMan and Bluetooth

About: Lazy Old Geek

April 2020 Update, thanks to a comment from a reader, Krasla, I'm now able to get into command mode with JDY-31s.

Going to try to enter Sensor contest.

So this Lazy Old Geek (L.O.G.) just completed a GPS project:


and was thinking about ways to communicate with the GPS. Well, I had some old Bluetooth modules lying around and decided to see if I could get them working. Now these were HC-05/HC-06 Bluetooth modules that I may have sorted got working but not very good.

So I did a lot of Internet research. One of the best resources I found was Martyn Currey:


Step 1: Bluetooth Testing

So I started to do some testing. Many sites explained that these modules required 5V to power the device but 3.3V for TX and RX.

Most of these modules consist of a base Bluetooth soldered onto a Baseboard. See pictures

Sorry, I don’t have actual pictures as I soldered the one I had.

HC-05 HC-06 what’s the difference. Well, the HC-05 can be a master or slave, the HC-06 can only be a slave. What??? Well, in many cases you only need a slave like if you want to talk to your smartphone. You would need a master and a slave if you wanted them to talk to each other, e.g., one Arduino to another.

One of the minor problems is that the base HC-05 and HC-06 look almost identical. (I don’t know maybe they are physically the same except have different firmware.

So I have an old Arduino called a Seeeduino which is nice because it has a switch that sets it to either 3.3V or 5V. I hooked it up this way:

BT Seeeduino

Gnd Gnd

5V 5V

Rx 9 SoftwareSerial BTserial(10, 9)

Tx 10

Install BTTest.ino (Zip file)on Seeeduino

Basically what the sketch does is takes serial data from the Bluetooth and sends it out the serial port.

Now as documentation says, these modules have two modes, one is command mode where you can setup the module, e.g., Bluetooth name, password and baud rate (communication speed). Well, for this test I just wanted to see if I can talk command mode.

So after playing around with baud rates in the sketch, I found that setting both the Bluetooth and the serial port to 9600 baud worked.

Another important setup for my modules is that the Arduino Serial Terminal must be set to (no line ending) and all commands must be in caps.

TIP: in order to use command mode, the module needs to be unpaired. Most modules have an LED that blinks when unpaired and is solid when paired.

DISCUSSION: So many websites discuss this. Different modules may have different baud rates, (sometimes 38400) and different line endings. I believe it’s just how the designer set the software up when it was being made.

So I can send AT commands and the version comes up as linvorV1.5. I’m pretty sure both my modules are HC-06 and I was able to change the Bluetooth name. See picture

Here's some of the AT commands:

Command Response Comments

AT OK Communicating

AT+VERSION linvorV1.5 Identifies device and software?

AT+NAME OKsetname Apparently can change the device name

AT+PIN1234 OKsetpin There is no indication that it’s changing the password. Apparently you have to disconnect power for it to work

AT+PN None Sets serial parity to None

AT+PO Odd Sets serial parity to Odd

AT+PE Even Sets serial parity to Even

Step 2: Bluetooth Testing 2

Okay, next step is to talk Bluetooth. So I have an Android smartphone and I tried an app called B-BLE. I couldn’t get it to work. Then I tried ‘Bluetooth Terminal’ This worked.

Procedure Smartphone

Go to Google Playstore and install Bluetooth Terminal.

Setup HC-06 with Seeduino (or CP2102) and connect to PC, open Arduino Serial Terminal.

On Smartphone, click on Settings, find Bluetooth, click on pair new device. If this is the first time you’ve connected you should see something similar this:


This is the HC-06s MAC address. Click on it

If not the first time, it will show the Bluetooth name, e.g., my2BT, click on it. See picture

It will ask you for Password, the ones I have are 1234. (If you have command access you can change the Password). See picture.

On Smartphone open Bluetooth Terminal app. It should open with Paired Devices screen, see picture,

Select the BT name, (my2BT).

By the way, this is where the BT module blinking LED should change to solid.

The Terminal screen should be displayed. See picture

Where it says “Enter ASCII Command”, type something to send to PC. Then tap (Send ASCII) (I have some of the BTNs programmed.)

The data entered should appear on the PC Arduino Serial Terminal. See picture

To send from PC, (I changed it to (both NT and CR) in command box, type what you want to send then click on (Send). It should appear on Bluetooth Terminal screen, see previous picture

Yay, we’re communicating!

Step 3: My Issue

As I mentioned before these modules are designed for 5V input and 3.3v signals. To me, this is the worst of both worlds. The proper way to use this is with a 5V Arduino, then convert the TX and RX levels to the correct ones. Some people use resistor dividers. Now I think my Seeduino even in 5V mode puts out 3.3V signals but other Arduinos don’t.

Now I am mostly using 3.3V devices like the Adafruit Feather M4 Express. The M4 Express does not have 5V power so how can I used these modules. One way is to use the bare HC-06 module without base but they’re harder to work with. What I decide to do was to convert my BT modules to 3.3V only. That’s what the big yellow 3 indicates.

With some Internet help, I came up with a couple of schematic versions of the JY-MCU BT module see picture and put them in Eagle Cadsoft, see zip.

TECHNOBABBLE: The BTI BCM is the Bluetooth and the rest is the base board. Unfortunately, there are many different base boards. Some don’t have the B1 diode, some have a P channel mosFET to enable the device. But in this case the main problems are B1 and the 3.3V regulator. With a 3.3V input you wouldn't get 3.3V to the HC-06.

So I jumpered the VCC input pin (5V) to the 3.3V on pin 12 of the module. Now I think that’s all that’s needed but I also removed the regulator (XC6206P332, but could be different type). From a technical viewpoint, I don’t think it’s a good idea to basically short the input and output of a regulator. I'm not going to explain this in greater detail as each base board may be different. See yellow wire in the picture.

So now these modules will work on 3.3V systems.

Step 4: Serial Adapter

So instead of using an Arduino on the PC, you can also use a USB-serial converter. The old Arduinos used the FTDI232 but they’re expensive, so I used to use PL2303 USB-serial converters. But since I couldn’t find a driver for the older models for Windows 10, I started using CP2102s. Now again the problem is the output pins all have 5V on them (coming directly from the USB connector). And there are many varieties. Anyway, I usually modify them for 3.3v and solder on a female header so it works with many of my Instructables projects. Now I also added a 3.3v regulator (L4931C33 I think) See picture. Most of the coverter ICs have a 3.3V output but I think most are limited to about 50mA. Actually, for just talking to the HC-06, 50mA is enough.

Okay so these can be hooked up to the HC-06 as follows:

BT CP2102

Gnd Gnd

3.3V 3.3V

Rx Tx

Tx Rx

See picture

Connect the CP2102 to PC USB. Now Arduino Serial Terminal is not the easiest to use so I tried Tera Term and Putty but they didn’t work very well, and I couldn’t figure out how to setup up for no line ending, so I’m still using Arduino. Works good.

Step 5: JDY-30/31 Bluetooth

So if you search on ebay for HC-06, they’re harder to find and you will often get JDY-30s instead. So since they seemed to be cheaper, I bought a couple actually from Aliexpress. They’re supposed to be compatible.

Some people and vendors claim that JDY-30 and JDY-31 are the same. I’m not so sure.

Anyway, the ones I got seem to be pin compatible and mine came on a similar base board as the HC-06.

Testing: April 2020 Update: Thanks to a comment from Krasla, I'm now able to connect to my JDY-31 in command mode. The main tip was that the "AT" command does not get a response but other commands like "AT+VERSION" works fine. And you do need to add CR + LF. Interestingly, I couldn't get this to work with Tera Term or Putty but it does work with Arduino Serial Monitor.

Anyway, so I decided to try this with Bluetooth. Using the same setup as the HC-06 I was able to connect with Bluetooth at 9600 baud.

Again the first time it is paired the device name will be a MAC address, but once paired the Bluetooth name is:JDY-31-SPP. Works good.

So I also found another BT called JDY-31, See pictures. What I like about them is that they have holes for a male header without needing a base board. See pictures. So I ordered a couple of these.

That’s my experience so far with Bluetooth modules.

Sensors Contest

Participated in the
Sensors Contest

Be the First to Share


    • Rice & Grains Challenge

      Rice & Grains Challenge
    • CNC and 3D Printing Contest

      CNC and 3D Printing Contest
    • Lamps Challenge

      Lamps Challenge



    3 years ago on Step 5

    I found that the maximum time between characters for the JDY-30 was about 30msec, any longer and the AT commands didn't respond. I couldn't get "putty" to past the \n\r at the end of the command :-(.
    However, sending the command from a python script worked fine.
    ====Begin python code=====
    import serial
    ser = serial.Serial('COM5',9600, timeout=1,bytesize=8, parity='N', stopbits=1,xonxoff=0, rtscts=0)
    while len(response)>0:
    print response
    response = ser.readline(80)
    =======End Python code=====

    Reply 2 years ago

    Thanks for the tips. I tried this with two JDY-31 using Tera Term but still couldn't get any response. Try at 9600 and various other speeds, still no response.
    Any suggestions?



    Reply 2 years ago

    I did connect to JDY-31-SPP using Tera Term and Arduino Serial Monitor using Arduino Nano, also with stm32f7 and stm32h7 flight controllers using serial pass-through and Tera Term as well, no success with Putty. And then I partially bricked the module by setting the speed to 9-230400bps. It would not allow me to set the speed to A, B or C so I set it to the highest it would accept AT+BAUD9, now it would not accept anything comming from the uart but would output data coming from BT side when paired but only with speeds between 124000 and 134000. Later I found the max speed of JDY-31 is in fact 128,000 and the pdf I was reading was for JDY-30. Here it is but be careful do not enter speed 9 as it will brick your module.
    Command Response Function
    AT OK Test command
    AT+RESET OK Module reset
    Read module version
    AT+VERSION OK Set module version
    AT+DEFAULT OK Reset module to factory
    Read MAC address
    AT+LADDR OK Set MAC Address (note 1)
    AT+NAME +NAME= JDY-31-V1.2 Read module name
    AT+NAME OK Set module name
    AT+PIN +PIN=1234 Read PIN
    AT+BAUD +BAUD=[1:C] Read Baud Rate:
    1: 1200
    2: 2400
    3: 4800
    4: 9600
    5: 19200
    6: 38400
    7: 57600
    8: 115200
    9: 230400
    A: 460800
    B: 921600
    C: 1382400
    AT+BAUD[1:C] OK Set Baud Rate
    1) There is no good reason to change the MAC address. MAC addresses should be unique
    and changing it could cause two devices to have the same address which would make the
    modules unusable together.
    Tera Term settings:
    Setup>Terminal. Select CR+LF for both Receive and Transmit. Also select Local echo.
    Setup>Serial port. Select your com port and speed of 9600. After you change the speed of the module with AT+BAUD you will have to match this speed to it to work. Do not set it to speed 9.

    If anyone has an idea of a way to connect to a uart @ 320,400bps let me know. The Arduino Nano is capped at 128,000 as well I believe.


    Reply 2 years ago

    Thanks for the information. I haven't used anything above 115200.



    Reply 3 years ago

    Thanks for the information. I'll try this again.



    2 years ago

    I'm trying and failing to get an HC05 into master mode so I can talk to several slave devices in turn. I have two types of HC05, one I've had for a few years, one JDY-30 is new.

    Testing HC05 is tedious and hard to be sure you repeat things correctly each time. So, on my breadboard the 5v power for HC05 is via a relay. The Arduino sets the HC05's ena+pin34 high then switches on the 5v. The Arduino is also transferring serial between Putty on the PC and the HC05.

    Both HC05 work in slave mode, I can type text between Putty on the PC and Blueterm on the phone.

    The older HC05 responds to a few AT commands at 9600. The JDY-30 doesn't respond to AT at any baud rate. Below are the responses from the older HC05: (bold)

    Anything that gets more functionality appreciated.

    +VERSION=+BOLUTEK Firmware V2.2, Bluetooth V2.1


    Reply 2 years ago

    So I'm going to try the same thing as I've ordered an HC-05 module. I haven't actually used one yet but found a video that looks pretty useful.

    Things to note: He uses a couple of resistors as a resistor divider on the RX pin of the HC05. As I think I mentioned these chips are 3.3V so should not have 5V signal on the RX. It might work fine with 5V levels (but might also be intermittent).
    He is using Arduino Serial and not Putty, I couldn't get Putty to work either. Also he is setting the baud rate to 38400 to communicate with the HC-05 in command mode. I think all of these modules vary but I found that command mode baud rate and operational mode baud rate aren't necessarily the same.
    Now it looks like when you send AT+ROLE=1 doesn't work.
    You might try AT+ROLE = 1 or AT+ROLE1
    If none of these work you might have an HC-06 instead of an HC-05.

    Here is are a couple of other Instructables that explains some of this:

    As for JDY modules, one thing I learned is that vendors do not always distinguish between JDY-30 and JDY-31.
    The other thing I learned is that the ones I have (JDY-30?) do not respond to "AT"
    but they do respond to other commands like "AT+VERSION". See Krasla comment.

    Good luck, hope this helps.



    Reply 2 years ago


    Thank you for your comments. I have a voltage divider to get 3.3v to HC05 RX.

    Putty works fine for me. It's said that HC05 requres a line ending of CRLF. That's ^m^j. Some commands work with just ^j and it accepts very slow typing.

    I tried your variations on +Role=1. It accepted AT+ROLE1 (big excitment) but on subsequent enquiry it is still zero (big letdown). I tried repower and it was definately Role=0.


    I bought these as HC05, but had realised that I can't prove that they are HC05. Strange, no label and no way to verify. There are some UK suppliers offering HC05 and easy to go to AT mode. I'll have to try one of them.

    Suddenly a little progress: I Googled the firmware name and found https://rurandom.org/justintime/w/Bluetooth_serial_modules. The commands don't want the ? on the end, and some don't work if it's there. Newly working:


    Can't see this being really useful if Role=0.


    Reply 2 years ago

    Thanks for the link. These HC05 modules don't all seem to be the same. It seems like some operate in command mode at different baud rates and their AT commands are slightly different.
    The JDY-30? I have use no CR or LF and don't respond to the AT only command.
    I hope your new HC05s work better.



    2 years ago on Step 5

    Those that work in the description, have not yet found others.
    P \ S The command "AT" itself does not work. only those on the list !!!


    Reply 2 years ago

    Thanks for the tip about 'AT' not working. Strangely, I couldn't get it to work with Tera Term or Putty but it did work with Arduino Serial Monitor. I was able to change the NAME and the BAUD which will be a big help to me. Thank you, again!



    Question 2 years ago on Step 1

    anybody work with JDY-19 BLE module?!