RE: Connection issues with Android smartphones

Lorenzo — Fri, 21 May 2021 09:33:21 GMT

Hi Simonr,

thanks a lot for your reply. We could try to disable DLE and use 1MBPS PHY but since the problem is only occuring with those particular smartphones and our application needs both features, the best thing at this time is to change the smartphones 🙂

Knowing this issue though it is probably better to disable DLE and 2MBPS PHY for general purpose applications where they're not necessary.

Thank you!

RE: Connection issues with Android smartphones

Simonr — Thu, 20 May 2021 08:02:46 GMT

Hi Lorenzo

The 2MBPS PHY is a BLE 5.0 feature, and from what I can see the OnePlus One and Samsung Galaxy A6 does not support Bluetooth 5.0, which would explain why you might see these errors there. For the Samsung Galaxy S8 I'm not sure what could cause this, but yes, The GATT ERROR (0x85) is a rather common Android error that can be caused by multiple things.

Do you see these errors if you use the 1MBPS PHY and/or disable DLE on your nRF application for instance?

2. I don't think compatibility mode will do anything for you I'm afraid, as what Sigurd mentions here is not very relevant in later products.

3. Compatibility mode 2 was removed from SoftDevice v5.0.0 as we added support for overlapping procedures, and this is enabled by default in the later SoftDevice versions and should take care of this issue.

4. I'm guessing that (at least two of) your devices are not supporting DLE which would cause issues. Are you able to take a sniffer trace of the connection to see if there is a connection parameter update on successful connections where DLE/2MBPS is disabled.

5. Are you using nRFConnect app for Android or the Bluetooth settings to connect to your device? I think the nRFConnect app should disable DLE by default if it's not supported, so that might not be the issue at all. Are you testing on a DK or on custom HW design? Are you able to reproduce this issue with a Development kit as the peripheral?

Best regards,

Simon

Side note: GATT error 133 is an infamous issue on Android and happens more often in older Android devices (older than Android 8.0), and some Samsung phones. The suggested workaround here is to add delays/retries when connecting to a device on the Android side.

RE: Connection issues with Android smartphones

Lorenzo — Wed, 19 May 2021 07:47:45 GMT

About question (2), I can already say there's something wrong because with this modification the device does not work at all (keeps rebooting immediately).