Automatically disconnection iOS

[Michel]

I'm using the NUS service for a sensor design. It was working fine for me. I don't know what is changed, but I experiences the next problem.

When I connect my sensor using an iOS app (own developed app, nRF Toolbox app or nRF UART app) the connection will be disconnected after about 95 seconds. When I connect it to the Master Control Panel on my windows PC or with a BLE Central device it will not disconnect automatically.

The sensor doesn't require bonding.

I don't know why it is disconnecting, but it looks it has something to do with iOS. By the way the iOS version 9.2.1.

Any idea what is wrong or how to solve it?

Thanks in advance.

UPDATE:

A Wireshark logging of the connection between the sensor and the iPod Touch 6th gen. ble_air_logging_2.pcapng

[run_ar]

Can you upload a sniffer trace that shows what is happening on air?

[Michel]

I made a sniffer trace and found that there is a "LL_TERMINATE_IND" about 95 seconds after the "CONNECT_REQ". The error code after the "LL_TERMINATE_IND" is 0x3B "Unacceptable connection parameter"

After 35 seconds a L2CAP Rcvd Connection parameter update request from slave to master was rejected by the master.

[Michel]

I found the MIN_CONN_INTERVAL and MAX_CON_INTERVAL values in my Nordic code where changed to small values. 10ms for the MIN and 15ms for MAX. After changing this value to 20 ms and 75 ms the connection with the iOS device remain stable after the 95 seconds.

I don't know why I changed it, but I did!

Problem solved for me at this moment.

[run_ar]

Glad to hear you solved the problem. iOS has strict rules for what connection parameter requests it will accept. You can see these in Apples Bluetooth design guidelines. Note that you can choose whether or not to disconnect in your application.

[run_ar]

Looks like the attachment function doesn't like spaces in the name. However, I guess it doesn't matter as you seem to have solved your problem :)