Bluetooth Module HC 05 not working properly

i am using bluetooth module , which is not woking properly...

it sends data to PC what arduino feeds it....!

but it dont transmit data from PC to Arduino..!

link to bluetooth module

what is possible solution

If anyone can answer?

You bump a post after less than twenty minutes? :astonished:

Are you using software serial for the BT module? Is your arduino powered with USB lead or power connector? What code are you using to read/write to PC over BT module (remember to post any code between code tags)

Code is working fine with normal arduino Serial Communication thru FTL 232 (onboard USb-Serial) . I am using NANO.

But when it comes on Bluetooth module , Data sent from Arduino is recived on PC thru Bluetooth .... But no data is sent to Arduino from PC thru Bluetooth Module

Try using software serial to send/receive from BT module to see it that works. I never had much luck trying to connect BT modules to UART RX/TX pins when powered over USB, I think the FTL232 interferes.

Whilst this thread has not not had a post for 120 days, I thought I would post my experience with the HC05.
I spent many, many hours getting nowhere with the HC05 module. I read many many posts and they did not get me very far very quickly.
The documentation is very vague & contains many errors.

I only had intermittent results if any at all.

My problems were that I was not paying much attention to the carrier board that the HC05 comes on. There seem to be significant variation of these. Some (like mine have a on-board regulator & some do not.

I was also paying to much attention to the warnings NOT TO APPLY 5V to these boards.

Well, applying 3.3 or so to these boards I was able to intermittently get into AT mode, but then the unit would refuse to operate in communication mode.

I tracked it down to the fact that the unit needs to have at least 3.8V connected to the board in order for the regulator to produce enough voltage to drive the HC05 module reliably.

It actually states on the board that the Vcc to the carrier board should be 3.6V-6V, but I reckon it should be 3.8V-6V or so.
In fact unless it is battery operated, connecting Vcc = 5V is the way to go!

Whilst the RX , TX & EN(KEY) are 3.3V , they seem to be +5V compatible as I have not had any failure.

Getting it into AT mode.
No instructions or circuit come with the carrier board. In my case it has a switch, but it was never clear what the switch is there for. However, I traced the circuit & I found that the switch connects between the KEY input & the HC05 and the KEY pin on the carrier board.
To put it into AT mode +3.3V needs to be applied to the KEY pin AND the push button must be pressed, while power is supplied to the unit. Once it is in AT mode
the 3.3V can be removed and the switch released.
A convenient method would be to run a strap between 3.3V on the HC05 module & the KEY pin.
Only pressing the switch is then required at power up.

It is all so bleeding obvious, once you know!

I hope these comments may help someone!

Only the RX pin is fragile and need to be feed with 3.3v signal
the easy way is a divider 1k/2k 2.2K/4.7 or even 5k/10k if it is not too noisy around and if you need to save a max of energy

My opinion: Do not purchase cheap HC-05 copycat modules from China (eBay).
I guess that these sellers still think that if they send 100 pieces, maybe 10 will work.

Some work, some don't, wasting hours of tinkering trying to find out what is wrong.
HC-05 is a fine module, but get one from a recommended supplier.