Samsung devices problem with nRF52840-DK throughput example (SDK 15.3.0)

[Or]

Hi,

I've install the throughput example (examples/ble_central_and_peripheral/experimental/ble_app_att_mtu_throughput) on an nRF52840-DK and I test it against all kind of phones to make sure the possible throughput is enough for my purposes.

I works fine against almost every Android phone except Samsung devices.

Works on:

1. OnePlus 5T
2. Xiaomi RedMi 8

Doesnt work against the following devices:

1. Samsung Galaxy S6
2. Samsung Galaxy Note 9
3. Samsung Galaxy S10

Here is how I perform the test:

1. I press "reset" button on the board and I get:
   

   [00:00:00.000,061] <info> app: ATT MTU example started.
   [00:00:00.000,061] <info> app: Press button 3 on the board connected to the PC.
   [00:00:00.000,061] <info> app: Press button 4 on other board.
   

2. I click button 3 on the board and I get:
   

   [00:00:03.129,638] <info> app: This board will act as tester.
   [00:00:03.129,638] <info> app: Type 'config' to change the configuration parameters.
   [00:00:03.129,638] <info> app: You can use the Tab key to autocomplete your input.
   [00:00:03.129,638] <info> app: Type 'run' when you are ready to run the test.
   

3. I write "run" and I get the following:
   

   [00:00:05.399,291] <info> app: Preparing the test.
   [00:00:05.399,291] <info> app: Starting advertising.
   [00:00:05.399,475] <info> app: Starting scanning.
   

4. I open nRF Connect on a phone and I attempt connecting to "NORDIC_ATT_MTU" .. the following happens:
   a. On Samsung phones it opens a new tab on the app and fails to connect after a while ("disconnect" on upper right changes to "connect") and nRF Connect log says:
       

   Error 8 (0x8): GATT CONN TIMEOUT

   
       The board log shows the following:
       

   [00:00:24.527,038] <info> app: Connected as a peripheral.
   [00:00:24.527,099] <info> app: Discovering GATT database...
   [00:00:24.527,160] <info> app: Sending PHY Update, 2 Mbps.
   [00:00:24.584,472] <info> app: ATT MTU exchange completed. MTU set to 247 bytes.
   [00:00:24.714,965] <info> app: PHY update rejected. PHY set to 1 Mbps.
   

   
   b. On other devices it opens a new tab, connects to the board successfully and lets me enable notification to the proprietary service thus starting the test.
       The board log shows the following:
       

   [00:00:38.663,330] <info> app: Connected as a peripheral.
   [00:00:38.663,391] <info> app: Discovering GATT database...
   [00:00:38.663,452] <info> app: Sending PHY Update, 2 Mbps.
   [00:00:38.750,305] <info> app: ATT MTU exchange completed. MTU set to 247 bytes.
   [00:00:38.885,192] <info> app: Data length updated to 27 bytes.
   [00:00:39.285,766] <info> app: PHY update accepted. PHY set to 2 Mbps.
   [00:00:39.466,674] <info> app: PHY update accepted. PHY set to 2 Mbps.
   [00:00:39.825,012] <info> app: Connection interval updated: 0x6, 0x6.
   [00:00:39.973,876] <info> app: Connection interval updated: 0x24, 0x24.
   

What is causing the problem with Samsung devices ?

Is this fixable on the board side ? on the Samsung phone side ?
Is this a matter of changing settings in the Android ?

I've tested this with SDK 15.3.0 and SDK 16.0.0.
Got same results.

Thanks

[Kenneth]

Hi,

Can you make an on-air sniffer trace? Download:
https://www.nordicsemi.com/Software-and-tools/Development-Tools/nRF-Sniffer-for-Bluetooth-LE

User Guide Documentation:
https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_sniffer_ble%2FUG%2Fsniffer_ble%2Fintro.html

If I were to guess I think it may be race condition, so you can try to add a delay in nrf_ble_gatt.c, for instance:

Best regards,
Kenneth

[Or]

There is something I dont get,

Surely you have nRF52840-DK lying around aplenty + it is probable that at least one of you guys have a Samsung phone + the problem is with an unmodified example in the SDK.

Why wont you install that example on an nRF52840-DK and test it against a Samsung phone ?

[Kenneth]

I can find a similar case:

https://devzone.nordicsemi.com/f/nordic-q-a/41644/ble-5-0-pairing-problem-throughput-test-with-galaxy-s8 

It's not that I don't want to help you, but if you can help in the debugging by providing the on-air sniffer log, then that would speed things up. Else I suggest to use one of the other BLE peripheral examples as a starting point, as suggested in the above case.