HC-05 cant pair


I´m trying to pair an HC-05 to my android phone, but when everyting is connected the status led on the HC-05 just blinks on an off every one second, and not the 5 flash is supposed to do and pairing is failed.

Can somebody tell me whats wrong?

Its connected like this:

HC-05 Arduino

RX -----------TX (voltage divider to 3,3v is used)
VCC---------5v pin

Best regards Emil

On my tablet, I have to go to the Settings and have the tablet find the HC05. Once it is found I can enter the password and it will pair. Then I can connect the HC05 to an app.

Describe the process that you follow to attempt to pair the HC05.

@mrmonza, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with your project. See About the Installation & Troubleshooting category.

In bluetooth settings i scan and find the HC-05 and when i click it to pair with my phone i get the message that pairing is not possible check device settings or try again.

I have not seen that problem before.

Post a photos of your HC05 module, front and back.

How is the HC05 powered? It should pair even if RX anf TX are not connected as long as it is getting 5V power.

Have you made any changes to the default settings of the HC0-5 by putting it into AT mode and making changes?

Incoherent. You say it can't pair but then say everything is connected. As mentioned above, you only need power and ground in order to connect Bluetooth to Android. When Bluetooth is ready to connect, the LED flash is about 2Hz. The flash when connected varies according to the model. I think the most common is solid, no flash, but It only needs to be different from the 2Hz to tell you it is connected.

IF the LED is flashing at about 0.5Hz, i.e. one flash every two seconds, you are in AT mode. You cannot communicate with the phone while in AT mode, but it may be possible for the phone to still see Bluetooth, and thus it is giving you good advice.

By connected i meant that the cables are connected between hc-05 and arduino.

Can the hc-05 be in AT mode by default? I have not made anny changes to its settings, and if i only power upp the hc-05 it flash on and off every one second.
i upploded a video when i power it up:

If its in AT mode how do i get it to data mode?

No. You might be confusing it with HC-06. Your Bluetooth is most unlikely to be an HC-06 as it has six pins. HC-06 routinely has four.

I am desperately trying to quibble with your video. I agree that it is flashing 1Hz but I have never seen that before. You are indeed keeping your paws away from the little button when you start up, and it appears that the pins at each end of the row are not connected.

Ah, just a minute. That is not an HC-05, I'm betting it is an HM-10. It so happens that HM-10 is in AT mode by default, but that isn't relevant - or shouldn't be, just don't send it any AT commands. You might find you can get more sense if you ensure you have the right sort of terminal for BLE comms, try that by Morisch. Once the point is proven you may need extra code. Frankly, I think HM-10 is more trouble than they are worth and their only purpose is to alleviate the woes of those who inflict themselves with iPhones. You may be better off ditching it for a real HC-05.

I agree with @Nick_Pyner . This module in your video is not an HC-05. It´s probably an HM-10 indeed. Thus, this is a BLE (Bluetooth Low Energy) module.

BLE is different from the common Bluetooth and it´s quite more complicated to deal with. It requires specific applications to "see" the data that is being exchanged. If you´re not used to BLE, you should consider getting an HC-05 or HC-06 module.

Thanks you are right it is an HM-10, the reason i thought it was an HC-05 ist because that was what i ordered but the chinese obviously shipped the wrong kind.

I will buy an HC-05 from an local store instead.

Again Thank for the help.

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