Connect BLE HID mouse to mobile phone or tablet

[Pedro]

Hi,

I've developed an application based on your BLE HID mouse sample. I commented out display and keyboard authentication callbacks so no passkey is showed nor confirmation is requested.

In a PC works OK, but with Android or IOS mobile phone or tablet, can't connect.

In Android it says "The device could not be paired because the access key or PIN is incorrect." and in IOS it says something like "It was not possible to connect, please ensure that the device is turned on and within range."

Is there any further step to connect to a mobile device? What am I doing wrong?

Thanks and kind regards,

Pedro.

[Pedro]

I update info. It's not a fact of being android o IOS device, the problem is once it is paired with a device, it stores the info in the flash and can't be connected to another until you make an "erase and flash".

Knowing that, How can I solve this issue?

Thanks again!

[Edvin]

Hello,

I am not sure I understand. Does it work if you don't comment out the authentication bits that you removed?

And what do you mean by:

Pedro said:

can't be connected to another until you make an "erase and flash".

Could it be that you are using bonding and whitelisting? Please let me know if you don't know what this means.

BR,

Edvin

[Pedro]

Hi Edvin,

I'm using bonding to automatically connect to yet paired devices. The problem is once you reach the max paired devices (CONFIG_BT_MAX_PAIRED) it does not automatically delete the oldest one to have space for the newest one. Just there is an error in the connection (Normally error 19, which implies host refused the connection).

I'd like to know how to delete oldest bond, if CONFIG_BT_MAX_PAIRED is reached.

Thanks for your help!

[Edvin]

Hello,

I see. So I assume that you have the peer_manager up and running, then.

You can use pm_peer_delete() to delete one  peer, or you can use pm_peers_delete() to delete all. 

In order to use pm_peer_delete() (to delete one), you need to have a peer_id which is a handle to the peer that you want to delete. 

To cycle through all your peers, you can use pm_next_peer_id_get(). To get the ranks of the peers you can use pm_peer_ranks_get(). Note that the ranks are not set automatically. You need to use pm_peer_rank_highest() (or *_lowest()) to set the rank of your peers, e.g. by which peer that was connected most recently. Read about it in the API descriptions from the links.

So let us say that you will rank the peer highest whenever you connect to a known peer. If your paired devices list is full, you can use the pm_peer_ranks_get() to find the lowest ranked peer, and delete it using pm_peer_delete().

Best regards,

Edvin

[Pedro]

Hello Edvin,

I didn't know about peer manager. I will investigate how to enable and use it.

Thanks for your help!

[Pedro]

Hi again,

I'm using Zephyr (NCS 2.0.2). Does peer manager you refer to applies to Zephyr?

[Edvin]

Sorry. I am mixing this ticket up with another HID ticket I have ongoing (which uses the nRF5 SDK). 

No, the NCS doesn't have a peer manager. I haven't looked into this in detail yet. What does the nRF log say?

Check out this guide from DevAcademy:

https://academy.nordicsemi.com/topic/blefund-lesson-5-exercise-2/

Looks like you can use bt_unpair().

BR,
Edvin

[Pedro]

Ok thank you.

Edvin said:

Check out this guide from DevAcademy:

https://academy.nordicsemi.com/topic/blefund-lesson-5-exercise-2/

Looks like you can use bt_unpair().

In this example it unpair all devices. 

Is there any example where unpair only the oldest paired device? I'm not sure how to know the info about all devices stores, and the age of them.

Thanks again! 

[Pedro]

Hi Edvin,

I found the solution. With Zephyr is much simpler. Just add 

CONFIG_BT_KEYS_OVERWRITE_OLDEST=y

in prj.conf.

I normally find difficult to find answers with Zephyr to simple problems like this.

What learning resources do you recommend for Nordic BLE from zero to expert, with Zephyr? Or to easy find answers?

Your courses are very good stating point, but what after that?

Thanks again!

[Edvin]

Glad you found a config that is working!

Pedro said:

I normally find difficult to find answers with Zephyr to simple problems like this.

What learning resources do you recommend for Nordic BLE from zero to expert, with Zephyr? Or to easy find answers?

That is a good question. It is a bit difficult to navigate in the NCS, as it is very general, and not a BLE specific, or even Nordic specific SDK. 

For BLE, I recommend the BLE course. The NCS Fundamentals course is also good for basic knowledge about NCS, and how Zephyr works. After that, I would say that the documentation would be the next place to look. A lot of stuff is very well described here. The difficult part is knowing exactly what to look for. 

The KConfig Reference may also be a good starting point if you are looking for configs for a specific thing. You can start typing, and it will show you all results. If you are using VS Code, you can also start typing a config in prj.conf, and it will show a lot of suggestions. This one I find quite useful, and I use it a lot. As you can see, it is quite forgiving, showing the CONFIG_BT_KEYS_OVERWRITE_OLDEST, even though I started typing something and skipped the "KEYS", so as long as you have a few keywords, it is quite easy to see if there are any matching configs:

Best regards,

Edvin

[Pedro]

Ok thank you for your tips Edvin!

Best regards,

Pedro.