Change MTU with nRF Connect for Desktop

[acanidio]

Hello,

I am using nRF Connect for Desktop 3.7.1 with a nRF52840 USB dongle for testing purposes.

In the Bluetooth Low Energy 2.5.3 application I deselected the "Auto accept update requests".
This shows me a view to request an ATT MTU exchange. The problem is that the field cannot
be edited but only accepted or discarded (correctly leading to a disconnection).

Is it a bug or the program is working as intended and I am missing something? I'd like something
like the “Request MTU” menu entry in the nRF Connect Android version.

PS: I saw a different ticket very similar to my request but I didn't find any answer that satisfies me:
devzone.nordicsemi.com/.../request-mtu-with-nrf-connect-for-desktop-as-gatt-client

Best regards,

Andrea

[Hakon]

Hello,

 

Is it a bug or the program is working as intended and I am missing something?

 I don't think this is intended, but I will check internally to make sure.

[acanidio]

Hi,

I checked the problem and it seems that it can be reproduced also with a normal NFR52-DK with the ble_app_hrs which supports DLE and ATT MTU longer than 23 bytes, so you can reproduce it yourself.

I flashed the ble_app_hrs_pca10040_s132 HEX file to the board and connected to it with Bluetooth Low Energy 2.5.3  the with a NRF52840 USB dongle.

Given the fact that I deselected the "Auto accept update requests" option on the nRF5x device what I get when I connect to the Nordic_HRM is the following screen, where DLE nor ATT MTU are not configurable but only acceptable. Am I missing something in the DLE and ATT MTU concept or is it a limitation of the app? Because I think this could be a very usefu yet simple feature to add.

ATT MTU exchange

DLE exhange

Best regards,

Andrea

[ovrebekk]

Hi Andrea

Sorry for the slow response. Håkon is currently on leave, and I will handle your case in the mean time. 

Would it be a workaround to simply change to a different data length and MTU after accepting the request, by using the Update data length... and Update MTU... functions here?

Best regards
Torbjørn

[acanidio]

It would be acceptable if it was possible.

I don't know how you can change the MTU after the initial accept request (or the Auto accept update request) since in my case the
Data Length is still configurable but the ATT MTU isn't.

For what I understood the ATT MTU can be changed once per connection according to BLE specification and Nordic followed
implemented the functionality correctly (while other silicon vendors allow multiple MTU change)

Hence I don't know how you manage your "Update MTU" because mine grays out when I both accept manually the MTU or auto-accept it.

Could you possibly explain it?

Best regards,

Andrea

[ovrebekk]

Hi Andrea

I am in talks with the software team to figure out if this is a missing feature in the application or not. I will try to get back to you in a couple of days with an update. 

Best regards
Torbjørn