HC05 standalone connected but won't send to terminal

Thread Starter

irmanao

Joined Apr 29, 2017
87
I have successfully send data to a terminal using the HC05 board but i can't do the same with my circuit that uses the standalone board. The pc recognizes the standalone version i made but nothing turns up in the terminal although i tested with oscilloscope and the TX signal is ok. I have a com configured for the hc05. The microcontroller controlling it is an stm32 so VCC=3.3.

The two boards seem different, does it matter?

Any ideas please?
thanks
 

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Thread Starter

irmanao

Joined Apr 29, 2017
87
What do you mean "standalone board"??
The wq pic i attached.
Also, the led i have connected as in the pic of my schematic attached, flashes quickly until connection with pc is made. Then the led flashes every time the serial data is sent but there is nothing in the terminal.
I tried 9600 and 38400 with no results.
 
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LesJones

Joined Jan 8, 2017
2,522
I think the HC-05 you have on the board with the pins probably has a regulator and possibly level converters as well a the basic HC-05 module. Do you have the data sheet on that board ? When you say "terminal" do you mean just a dumb ASCII terminal such as a Dec VT00 or similar ? What signal levels are you converting the RS232 signals from the terminal to to connect to the HC-05 ?
The 100 pF decoupling on the 3.3 volt rail seems very small (I would have used a 100 nF) but I don't think that is the cause of you problem.
I suggest that you try connecting RX to TX on the HC-05 and check that you can see the character you type on your PC are being sent back top the PC (I.E. You see them displayed on the BC screen.
Did you have any problems while configuring the HC-05 from the terminal using the "AT" commands ?

Les.
 

Thread Starter

irmanao

Joined Apr 29, 2017
87
Yes i know the board with the pins has a regulator. I don't have the exact datasheet, i found one similar to my schematic and copied it.
I am using the uart of a microcontroller and teraterm on the pc, so no rs232 signals. I am not using any AT commands (don't know how).
However now, the led i connected isn't flashing at all sometimes...
 

spinnaker

Joined Oct 29, 2009
7,837
The wq pic i attached.
Also, the led i have connected as in the pic of my schematic attached, flashes quickly until connection with pc is made. Then the led flashes every time the serial data is sent but there is nothing in the terminal.
I tried 9600 and 38400 with no results.
I don't think you can just leave all of those pins open. Why not just use two full HC05s?
 

spinnaker

Joined Oct 29, 2009
7,837
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Thread Starter

irmanao

Joined Apr 29, 2017
87
Thanks for the answers guys. It weirdly connects to my mobile phone fine and sends to its terminal....
The pc still recognizes it and the led flashes slower when connected.
Any ideas what could be wrong?
I have already made the board so i want to make it work (i know i should have researched it better)


Update: Even weirder, it now sometimes sends to the PC terminal and others not at all..
There must be something going on with this new device and the PC's bluetooth because there are no issues with the mobile phone
Update 2: It's working now but it takes a long time for connection establishment and i have to delete the hc05 from the pc everytime. Must be something wrong with the firmware with windows 10.

thanks for the help
 

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spinnaker

Joined Oct 29, 2009
7,837
I have had a whole host of issues with those devices, including some you mentioned. I have found that manually removing the device from windows, rebooting and adding again solves some problems.
 
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