Android and BLE connectivity issues

[brinehart]

Hello,

We are currently using a Raytac SoM that has nRF51822 SoC with Adafruit UART firmware. We are running into two different scenarios BLE connectivity issues where the android device:

-will no longer see the the SoM broadcasting unless the android is power cycled

-will not be able to connect for a period unless the android device power cycled

In both of these cases, sometimes resetting the bluetooth controller on the android fixes this and sometimes it doesn't.

We have used the multiple different android devices and have found that some devices frequent these issues more than others. We also found that exact same model androids react differently and worse than others.

Has anyone else seen or experienced this? Are there any phone settings that could be causing the two above issues?

Is there a "best fit" Android device/OS that pairs with nRF51822 SoC?

Any and all advise welcome. Thank you  

[brinehart]

We have isolated the issue to the central device.  
Although not consistent from device to device, most often we are seeing these failures with the Blackview(BV6800-pro).
We have tested using our application and nrfUART. When failing, the Blackview will not see the broadcasting ble modules, and unable to connect. Meanwhile a Samsung(galaxy tab A) tablet, can connect with no issue, however this tablet is seeing a less consistent second issue, that has yet to recreated. 
This device to device inconsistency is our main concern.

Finding a predictable consistently operating central device is our key objective.  

[brinehart]

I have found that with the Blackview android device. If the phone is paired with the nrf51 module, the android will eventually be unable see broadcasting or connect to any nrf51 modules, but the android can still see/connect to tablets and any other bluetooth devices. Meanwhile the Samsung tablet connects with no issue while paired.

[Hung Bui]

I'm not sure what could be wrong with the Blackview phone. However, what you can try is to disable wifi and check if it improves the performance. 
If your phone only connect , not pair to the nRF51 module, would it has the same problem that it can't connect to other nRF52 devices ? 

Note that connecting to other tablet or phone is not Bluetooth Low Energy, it's Bluetooth classic so it's not really related. 

[brinehart]

I have not tested this with nRF52 boards yet.
The main objective of this post is to find suggestions on best/most compatible android devices to try, with their operating systems, and BLE versions. 
Does nordic have their go-to or favorite android device that works best for them?

[Hung Bui]

Sorry I mean to test with other nRF51 devices ( when you don't pair, just connect). 

We don't have a list of favorite devices as our softdevice (BLE stack) is qualified for Bluetooth Low Energy and it should work with any device that is BLE certificated. We have thousands of user with hundreds of million of product on the market now so in most cases it works fine with any phone.