Hi Vinayak

> A btmon log would help identify the reason for disconnection.

I have uploaded the 2 logs here: https://www.dropbox.com/s/d2yurf6nxee9wk0/btmon_logs.zip?dl=0

The Zephyr one has quite a lot at the beginning before I made the connection. Here is one of the disconnect events from the zephyr log file:

< HCI Command: Disconnect (0x01|0x0006) plen 3           #624 [hci0] 292.906310

        Handle: 0

        Reason: Remote User Terminated Connection (0x13)

> HCI Event: Command Status (0x0f) plen 4                #625 [hci0] 292.907421

      Disconnect (0x01|0x0006) ncmd 1

        Status: Success (0x00)

> HCI Event: Disconnect Complete (0x05) plen 4           #626 [hci0] 292.923423

        Status: Success (0x00)

        Handle: 0

       Reason: Connection Terminated By Local Host (0x16)

@ MGMT Event: Device Disconnected (0x000c) plen 8    {0x0002} [hci0] 292.923459

        LE Address: DC:59:20:76:11:5C (Static)

        Reason: Connection terminated by local host (0x02)

@ MGMT Event: Device Disconnected (0x000c) plen 8    {0x0001} [hci0] 292.923459

        LE Address: DC:59:20:76:11:5C (Static)

        Reason: Connection terminated by local host (0x02)

> > the connection parameter update still fails but even minutes later I am still connected to the remote device.

>

> This is weird, the cypress dongle did not perform connection parameter update, update procedure on air only either succeeds or disconnects (unless it’s a connection parameter request procedure that is rejected by peer).

Yes, that is what it is, apologies:

> ACL Data RX: Handle 0 flags 0x02 dlen 16                #179 [hci0] 69.454378

      LE L2CAP: Connection Parameter Update Request (0x12) ident 2 len 8

        Min interval: 6

        Max interval: 12

        Slave latency: 0

        Timeout multiplier: 400

< ACL Data TX: Handle 0 flags 0x00 dlen 10                #180 [hci0] 69.454425

      LE L2CAP: Connection Parameter Update Response (0x13) ident 2 len 2

        Result: Connection Parameters rejected (0x0001)

Thanks,

Jamie