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]

Hello Martin, thanks for your support. Our custom application was developed from an older SDK with an older S110. The thing is that it should work regardless the software setup we are using, right? Our application works perfectly with any iOS device and Android device (including Nexus 6 with Android 5.x). However, after upgrading the Nexus 6 to Android 6.0, it does not connect anymore, while the Nexus 5 (for example) with Android 6.0 it does. I've just tried to connect the Nexus 6 with Android 6.0 to our peripheral device by using the nRF Master Control Panel app but it failed as well. Are there specific improvements related to connection establishment in the newer SDK/S110 software versions which would explain this missbehavior?