Working with Bluetooth modules

So hello everybody!

I have couple of problems with my Bluetooth modules.

At first, I have Bluetooth module HC-05, and when I put it on 5V, LED blinks 1Hz, so it means it is in AT mode, with my program code, I can make it go master or slave with AT+ROLE0/1, some of AT doesn't work. But ok, the problem with this module is I can't pair it with my smartphone, i press to pair and it says device can't pair. I can't pair because LED is blinking 1Hz so it means it is in AT, I can't exit AT mode, can somebody give me advice how to exit it ?

Second problem, my HC-09, I can pair with him but when i go to Bluetooth serial I can't connect to it, I can't connect, but I can pair with it.

Somebody have some advice ? I really tried everything, enterint AT mods on different way, but I can't make my module to exit it, and to start LED blinking fast what means that I can pair with it. HELP ON! Thank you guys and girls!

majki4: I can't exit AT mode, can somebody give me advice how to exit it ?

You're saying that your situation is that all you do is power it on and it is in AT mode (already)?

AT mode is 1 sec On, 1 sec Off

Yes, that is what I am saying.

I plug it on 5V, and it is blinking 1s on, 1s off. That is AT mode. I tried everything to exit it, so I can pair module with my smartphone, but nothing helps.

It is supposed to blink very fast, what means it is ready to pair, but no..

You're saying that you can send AT commands and get replies via 'serial terminal' with no additional steps? Getting an HC-05 into AT mode is a simple thing, but requires deliberate action (it's not accidental). "I tried everything to exit it..." How did you get it into AT mode?

In the Martyn Currey article that I linked in my previous reply, he describes a "Method 4" where AT mode is cancelled (exited) by "sending a $ (character)"

I just plug it in and it was blinking 1sec on /off.

Yes i tried his method, I can use the AT command, some of them are working some of them not. I can change AT+ROLE to 0 or 1, when i hit ROLE1, it is master, LED is blinking 2Hz, faster then on ROLE0, but then I can't see it in Bluetooth devices, at ROLE0 I can at least see it, but I can't pair it. I really have no idea how to make it to pair with my smartphone..

HC-05 and HC-06 are in AT command mode as long as they are not connected to a master. As soon as they connect they switch to pass thru mode. You can also force pass thru mode on the HC-05 using an AT command.

What kind of smartphone do you have? HC-05 and HC-06 do not connect to Apple iOS products (iPhone,iPad) as Apple does not support the protocol implemented (SPP I think).

Can you see the BT device on a Windows PC?

What is command to switch to pass thru mode with AT commands ?

I have Samsung Galaxy S6, I already worked with my last module, but I burned it down so I got myself a new one.

I can see BT device on my phone also, but I can't pair with it. Funny fact, now I see I can connect to that module on my laptop, I will try with that, but still i don't get why can't pair on my smarphone.

What is command to switch to pass thru mode with AT commands ?

Connect to a Remote Device
where = 48 bit bluetooth address
in NAP,UAP,LAP format

If you have not already done so, get a datasheet for the module. They list all the AT commands.

but still i don’t get why can’t pair on my smarphone

Have you tried Google? I am sure you are not the first.

IIRC I had one do this. I had paired it with my phone then unpaired and paired with my son's. Then he went to bed and it would power up and think it was still paired with his. Took a while before I figured it out and had to go in his room and unpair with his. Did you maybe have it paired with a different phone/tablet and forget to unpair?