Pairing works only on some android phones

[Midhunjac]

Hi,

I am modifying the peripheral_uart code to set a fixed pairing method so that I will have to enter a pre-defined passkey in my nrf connect application on my android. It works fine with my android. So I assume my callbacks and workflows are all fine. However, when I try to pair from some other phones, it does not work anymore. I am not even prompted for a passkey in other phone. In some phones, pairing fails with an error message on central (android) side with message 'Couldn't pair with Nordic_UART_Service. Make sure that it's ready to pair' . After this, every attempt to pairing fails without any messages. For some other phones, we do not even see a message. The central says 'Bonding..' and then says 'Not bonded'.

The logs in the peripheral side does not say much either.

I cannot use Just Works or fixed passkey for pairing here. I am using NCS V2.1.0 and nrf52832DK

have anyone faced this kind of problem ? Any help would be appreciated. Thank you

[Menon]

Hello,

From the log you shared I can see that Disconnect reason is 19, which is not an error. This just says that the peer decided to disconnect for some reason. This can be device specific, or may be because of something else (can be some other app) is running in the device.

Could you also share the Phone details you are trying with? I can check if there is any reported issue about this.

Kind Regards,

Abhijith

[Midhunjac]

Hi,

I am using two Samsung phones - one running Android 8 and one running Android 11 (J and M series respectively.)

I have a UART command to switch between Just Works and fixed passkey mode

One another observation is as follow.

Initially it was seen that the Android 8 one could not pair successfully. But Android 11 phone could pair( Note that there were still other Android 11 phones that could not connect. But that is not related to the observation). After a lot of pairing attempts and failures and switching between the Just Works and Fixed passkey methods, somehow in one random particular attempt,  the Android 8 could pair in either Just Works or Fixed passkey method. Which means, somehow the problem was solved on its own. Now I unpair the Android 8 phone and I check the Android 11 phone in which pairing was successful before. But it can no longer pair in either mode. Repeating the same cycles ( i.e pairing attempts failures and switching between different pairing methods using UART commands ), on one random attempt, I could pair with Android 11 phone. But as expected, when we try that on Android 8 ( after disconnecting Android 11), pairing no longer works.

I hope I was clear about the whole incident. But I have no explanation for this behavior. Does this make any sense ?

Thank you