Multiple pair support but no simultaneous connection

[Ih3b]

Hello everyone,

I'm using the Bluetooth peripheral sample and I'm in a scenario where I want to connect to my board from only one device at a time, meaning I don't want multiple simultaneous connections. However, I also have pairing activated. So, I set my parameters in the .conf file like this:

CONFIG_BT_MAX_CONN=1
CONFIG_BT_MAX_PAIRED=1

I'm not interested in bonding devices to the flash, so I commented out the following parameters:

# CONFIG_SETTINGS=y
# CONFIG_BT_SETTINGS=y
# CONFIG_FLASH=y
# CONFIG_FLASH_PAGE_LAYOUT=y
# CONFIG_FLASH_MAP=y
# CONFIG_NVS=y

The issue is, when my board is ON and I try to connect to it from my phone, I can connect and pair. But when I switch to another phone, I can connect but not pair. So, I changed the settings to:

CONFIG_BT_MAX_CONN=1
CONFIG_BT_MAX_PAIRED=128

Now, I have no simultaneous connections, but I can pair with any device (assuming I don't exceed the maximum).

Can someone confirm if this is a good solution? I think it's just a workaround, and I might be missing something.

Thank you for your help!

Iheb

[Vidar Berg]

Hello,

# CONFIG_SETTINGS=y
# CONFIG_BT_SETTINGS=y
# CONFIG_FLASH=y
# CONFIG_FLASH_PAGE_LAYOUT=y
# CONFIG_FLASH_MAP=y
# CONFIG_NVS=y

Yes, if you don't want to support bonding, but only pairing, you can comment these. In addition, you should add CONFIG_BT_BONDABLE=n to your configuration file to prevent bonding.

The BT_KEYS_OVERWRITE_OLDEST setting is only relevant when bonding is supported. CONFIG_BT_MAX_PAIRED should also be left at the default value ('1').

[Ih3b]

With bondable set to 'no', when I pair and then disconnect and reconnect, my board forgets the keys, and I must pair again. I want to retain the keys to remember my device while my board remains powered on (it's acceptable for the keys to be lost once rebooted or unplugged)

[Vidar Berg]

Have you considered if this may have implications on the user experience? If a bond is deleted on the device but not on the phone, you may need to prompt the user to manually delete the bond on the phone before reconnecting.

[Ih3b]

As I'm testing with nRF Connect for Mobile on two different Android devices, I found that I don't have to delete the bond on the phones because the device requests pairing again when switching between phones.

With :

CONFIG_BT_MAX_CONN=1
CONFIG_BT_MAX_PAIRED=1
CONFIG_BT_KEYS_OVERWRITE_OLDEST=y

Phone A connects and pairs with the device, and when disconnected and reconnected from A, the device recognizes it.

Now, I disconnect from Phone A and use Phone B.

Phone B connects and pairs with the device, and when disconnected and reconnected using Phone B, the device recognizes it.

When I switch back to Phone A, it will ask to pair again because i was paired with phone B.

Do you think if I change nRF Connect Mobile to another application, the user would still need to manually unbond? because i don't see a problem with that with nrf connect for mobile..

What do you think ?

Thanks in advance Vidar

[Vidar Berg]

It is not so much about which app your are using, but more with the Bluetooth framework you are working with. Have you tried this on iOS as well?

[Ih3b]

Yes, and it works..

[Ih3b]

So no worries to leave it like that ? Vidar Berg