Android disconnect issues

[KV]

I am using HRM demo application on nRF52840 DK with Samsung Tab-A. The nRF Connect App is running on the tablet. We are seeing that the dev kit gets disconnected soon after a connection is established. The error code on peripheral side is 0x2A.

Android version is 7.0 Device model number SM-T580 Bluetooth version 4.2

This does not happen on iPhone 7 with the nRFConnect app.

Also, this does not happen on LG Nexus 5 smartphone running Bluetooth version 4.0.

[Hung Bui]

@KV: Please provide a sniffer trace.

Please state which SDK and which Softdevice you used. Also please confirm you have disconnected reason = 0x2A = BLE_HCI_DIFFERENT_TRANSACTION_COLLISION, this disconnect reason usually happens when the peer (the phone) violate the spec and send 2 LL link layer request without waiting for response. In S132 we allowed the behaviour. From release note:

The SoftDevice slave role now accepts overlapping peer-initiated Link Layer control procedures (DRGN-8623). The following LL control procedures can be executed in parallel with any other control procedure, except for themselves: LEPing, Feature Exchange, Data Length Update, and Version Exchange. This is done for compatibility reasons.