NRF Connect: failed to call gattsExchangeMtuReply (NRF_ERROR_INVALID_PARAM)

[paul]

Hi Nordic,

I'm trying to use a nrf52832 dev kit (v1.1.1) with NRF Connect (v2.5.0 on mac) to communicate to my device (NRF52832). My device has implemented MTU exchange using SDK 15.1.0. However, upon connection, NRF Connect throws an error related to MTU reply. Note that I've tried running "msddisable" on j-link on the DK. 

In my device logs, I don't see anything strange, but the NRF connect thinks that the remote user terminated the connection.

Is this a known issue?

[Mttrinh]

Hi, 

Have you tested with nRF Connect on PC? Do you see the same issue there?

[paul]

Yes, same error message occurs on Windows.

I've experimented a bit and found that setting NRF_SDH_BLE_GATT_MAX_MTU_SIZE to 248 in the NRF52 with which NRF Connect is connecting (basically, my device under test) triggers the issue. Setting it to 247 seems to make the issue go away. Value in NRF_SDH_BLE_GAP_DATA_LENGTH seems to have no effect.

Is this a bug in NRF connect?