Nrf Connect for PC fails to negotiate ATT_MTU > 247 bytes

[Peter Kenyon]

Using nRF Connect for PC Version 2.6.1

Connect to a peripheral device that ask for an ATT_MTU > 247 bytes

NRF Connect fails with 

Failed to call gattsExchangeMtuReply (NRF_ERROR_INVALID_PARAM)

This is a show stopper

[Peter Kenyon]

It works OK with a PCA10031 and sets an MTU of 23 bytes.

It doesn't work with a PCA10059 or a Nrf5240 DK

[Sigurd]

Hi,

I see that you wrote in this post that the negotiation fails. Are you still able to maintain the BLE connection to the peripheral after this happens? 

[Peter Kenyon]

Nope the connection gets dropped with Disconnected from device C0:3B:56:B0:AB:1F, reason: BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION, (probably caused by a gattc timeout on peripheral)

[Sigurd]

Thank you for reporting this. This is a bug in nRF Connect BLE app, and I have reported it to the nRF Connect developers.

[kobyatom]

same error message here, with #define NRF_SDH_BLE_GATT_MAX_MTU_SIZE 255. 
cannot stay connected.
Did not find any related error in the text log file of the nRF connect application.