Peripheral fails to establish connection with certain parameters

[RPDben]

Hi,

I am using the nRF52840 on a custom board with SDK15.2.0 with SD S140 6.1.1.

My current BLE connection parameters are below which allow connection to the nRF Connect app and my custom Android and iOS app.

Min Connection Interval	7.5ms
Max Connection Interval	125ms
Slave Latency	1
Supervision Timeout	1000ms

I am having issues with data transfer on the iPhone 7 where the connection is being unexpectedly dropped during the transfer of data. In order to try to fix this, I wanted to align my connection parameters with the Apple specified ones. However, whenever I increase the minimum connection interval (e.g. to 15ms) and try to connect with the nRF Connect PC App I get an immediate disconnection with the error reason: BLE_HCI_CONN_FAILED_TO_BE_ESTABLISHED.

Any thoughts as to either of my two problem would be much appreciated:

1. Why the iPhone 7 is failing to complete a data transfer (other versions of iPhones, both older and newer, are working just fine)
2. Why I cannot change my minimum connection interval without causing issues with connection

Thanks in advance,

Ben

[awneil]

With Android, there is a BLE HCI log which you can look at to see what's going on - does iOS have a similar facility?

What event(s) are you seeing at the peripheral side?

[RPDben]

I have sniffed the connection and it just stops. There are no HCI events or similar picked up by the sniffer. I don't know if iOS has an HCI log facility unfortunately

[Joakim Jakobsen]

Maybe you could upload the sniffer trace, so that I can take a look at it?