RE: Connection problems depending on the Smartphone with nrf52840

Einar Thorsrud — Thu, 22 Apr 2021 13:38:01 GMT

Hi Dani,

[quote user=""]- Depending on the Smartphone, we are not asked for the PIN when pairing/bonding the first time.[/quote]

With iOS bonding is only initiated when needed, which is after being denied to read/write to a characteristic. Once that happens, the iOS BLE stack will initiate pairing/bonding. I suspect that is what you are seeing here.

[quote user=""]- In some smartphones, it takes a lot of time (even when already bonded) to stablish connection: maximum time should be 10" (advertising period) but sometimes, it takes more and more time.[/quote]

Can you clarify what you mean by 10''? (It does not match your APP_ADV_INTERVAL value of 80 = 50 ms). Please elaborate.

[quote user=""]- When it takes a lot of time to connect, sometimes smartphone is able to connect when bluetooth is switched off and switched on again. But this is not happening with other devices, only with this one we have designed. Is it something related with parameters we have set up?[/quote]

It is not clear to me exactly which advertising parameters you use (see above). But generally you can come into a situation where the phones scan window does not overlap with the peripherals advertisement packets for a long time if the scan interval and advertising interval re very similar (or advertising interval is a multiple of the scan interval). If they are not identical, they will drift to overlap at some point though. For this reason Apple has recommended some advertising intervals that work well in the Accessory Design Guidelines for Apple Devices. Following those is generally a good idea. Also, some phones in some situations may have much less time for scanning, for instance if they allready have a lot of other BLE or other 2.4 GHz activity going on.

Einar