Galaxy Tab A8 (SM-X200) Connection Issues with GATT Error 133 after multiple connecting failures

Hello,

we are currently experiencing a lot of trouble with a product of ours which has been used in the field since a long time but was only compatible with iOS devices so far. We are now close to publishing an app for android as well and have been testing with a number of devices.

The Gatalxy Tab A8 is however giving us a lot of trouble. It is a relatively new android tablet device and needs to be supported.

How to reproduce:

- The App tries repeatedly to connect to a bluetooth device of ours, running our custom firmware

- If the RSSI to a test device is below -75 / -80, the connection procedure repeatedly fails very often to establish a connection

- If the connection fails for a number of times (e.g. around 100 times), the tablet seems to be in a state where it will not connect to nRF devices anymore

- The device will however be able to connect to non nRF devices (e.g. an Apple TV or some other 3rd Party devices)

- We used the pre-compiled nRF52832 and nRF52840 examples for the peripheral heart rate monitor service to establish a connection, but the connection always fails for SoftDevice 5.1.0 and SoftDevice 7.1.0. We have tried this connection using an app from the PlayStore called "LightBlue".

- We have used PCA10040 and PCA10056 for testing.

- Trying to connect to an nRF device with with the HRS example app fails until we disable bluetooth on the Galaxy Tab for some time and then activate it again.

- We have also tried to keep nRF devices off until the tablet is in its "failure state" to be sure it is not linked to devices that were previously discovered.

It looks like the tablet can go into some state where it will become incompatible with nRF devices until the Bluetooth Stack has been rebooted.

Can anyone help me with this?

Side Note: Maybe this can be a similar issue to these that are also linked to nRF devices:

Samsung Galaxy Tab A8 does not work with nRF Mesh Android App - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)

DFU fails with "Characteristic write error: 133" on Galaxy Tab A8 · Issue #339 · NordicSemiconductor/Android-DFU-Library (github.com)

Thanks,

Marius

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