Connection issues with Android 6.0 Marshmallow and Nexus 6

[Mario Amigot]

Since Google released Android Marshmallow 6.0 we are experiencing problems when connecting our nRF51822 based peripherals to a Nexus 6 phone. The Nexus 6 is able to see our peripherals' advertisements while scanning but when it initiates a connection to a peripheral by sending a CONNECT_REQ packet, in that specific nRF51822 the BLE_GAP_EVT_CONNECTED event is never thrown by the S110 softdevice stack so the connection is never established. The thing is that the same application run in a Nexus 5 with Android 6.0 works without any problem.

Has anybody experienced similar issues with Android 6.0 and Nexus 6? Any idea what may be going on or a solution to this?

[Mario Amigot]

I've forgotten to mentioned that I confirmed with the help of a BLE sniffer that a central device (in my case was a Samsung Galaxy S6) running Android 6.0 does not send the CONNECT_REQ packet when trying to establish a connection with a peripheral device (nRF51822) with random address. However, changing the address to a public one the connection is established correctly.