Problems with HC-05 bluetooth module

[reza147]

Hello
Problems with HC-05 bluetooth module.
When i turn on the module a led in hc-05 be blinking fast. This indicates that the module is in DATA mode. In this case, when I search the phone with Bluetooth, it correctly finds the Bluetooth module named HC-05.
When i hold Key_module (or connected EN_pin to VCC_pin) then conncted power to module, Now the led on the module will blink at the interval of 2 seconds. That means it has entered the AT mode?! (then i release Key_module or EN_pin)
But when i send "AT" command, module no respons. (i test with VCC=3.3v or 5v/ with 1200 to 230400 boud rate). Also I search the phone with Bluetooth,but not finds the Bluetooth module.

Having multiple bluetooth modules with the same name can be confusing. i attach pic of my module. Please tell if anyone can help .

Rx pin of the Bluetooth module to Tx pin of USB to TTL converter, and Tx pin of Bluetooth to Rx pin of converter. Also connect their ground to power_GND. (connect their Vcc to 3.3v or 5v)

 

[FvM]

HC-05 AT command interface is a bit tricky.
- AT interface is case sensitive
- commands must be terminated with <CR><LF>, most terminals don't provide it. I'm usually typing CTRL-M + CTRL-J instead of Enter key.
- Baud rate is 38k4

--- Updated Jun 8, 2021 ---

Module name can be programmed in AT mode

 

[reza147]

Hello
I respect the buadrate and case sensitive and hardware. (I think)
But i could not get the"OK" from HC-05.[ when i send "AT" command, module no respons.]

Please let me know if anyone has worked and received an answer. (Exactly with the same module that I sent in the photo)
thanks

 

[KlausST]

Hi,

Can you show a photo of your wiring (including HC-05 module and USB converter)

Klaus

 

[FvM]

It seems like I'm using the same modules. I connect it to PC with FTDI USB to 3.3V TTL cable to setup the configuration.

 

[FvM]

Additional information, I have the "EN" pin (driving pin 34 of the original HC-05 module) bridged to VCC, thus 38k4 baudrate is selected. Corresponds to holding the button during power-up.

 

[reza147]

HC-05 AT command interface is a bit tricky.
- AT interface is case sensitive
- commands must be terminated with <CR><LF>, most terminals don't provide it. I'm usually typing CTRL-M + CTRL-J instead of Enter key.
- Baud rate is 38k4

--- Updated Jun 8, 2021 ---

Module name can be programmed in AT mode

Hi
how i to send "CTRL-M + CTRL-J instead of Enter key" on the "Tera Term".

--- Updated Jun 14, 2021 ---

Additional information, I have the "EN" pin (driving pin 34 of the original HC-05 module) bridged to VCC, thus 38k4 baudrate is selected. Corresponds to holding the button during power-up.

View attachment 170077

Hi.
When i hold Key_module (or connected EN_pin to VCC_pin) then conncted power to module, Now the led on the module will blink at the interval of 2 seconds. I search the phone with Bluetooth,but not finds the Bluetooth module.
For this case, can your module be detected by the phone?

 

[FvM]

Hold the CTRL key and press "M" and "J".

I believe, you can also set up Tera Term to send CR+LF in the terminal settings.

Please notice that I'm using Putty rather than Tera Term, thus I'm not completely sure about the behaviour.

 

[reza147]

Hold the CTRL key and press "M" and "J".

I believe, you can also set up Tera Term to send CR+LF in the terminal settings.

Yes, thank you. But I still do not receive "OK".
Since these modules are similar, is it possible that the HC-06 type was assembled incorrectly?
If it is HC-06 type, does it not respond to AT commands?

 

[FvM]

Transmit CR+LF option seems to work

And don't forget to set flow control to "none".

 

[reza147]

Hello
Thank you.
Unfortunately, it did not work.
I plan to get another Bluetooth module and test it.

 

[KlausST]

Hi,

We currently have nothing "objective" to validate. We see your text, but this is "what you expect".

If you want us to validate something, then post photos (small file zize) of the complete wiring and screenshots.

Klaus

 

[FvM]

Not sure what's the problem, may be interchanged Rx and Tx lines?

 

[reza147]

Hi,

Can you show a photo of your wiring (including HC-05 module and USB converter)

Klaus

Hello
We provided another module for Bluetooth testing. This module is headerless and SMD type (HC-05). We tested this converter. This module answered us correctly.
So in this case I can be sure in terms of hardware connections and terminal software.
But still the first converter with the header does not work (HC-05 Board). (I even opened it from the header and tested it as SMD)

--- Updated Jul 6, 2021 ---

Hi,

We currently have nothing "objective" to validate. We see your text, but this is "what you expect".

If you want us to validate something, then post photos (small file zize) of the complete wiring and screenshots.

Klaus

Yes thank you. We waited for the second Bluetooth module, which is of a different type, to arrive and test it.