Softdevice couldn't initiate connection successfully

RE: Softdevice couldn't initiate connection successfully

Edvin — Tue, 02 Nov 2021 13:33:58 GMT

Is there any other places in the application you may call something that updates the MTU? E.g. somewhere in main.c?

[quote user="alireza sadeghpour"]1) what is the LL_FEATURE_REQ and is there any way to send that request with the soft device?[/quote]

I don't think that is an active application call. I think the softdevice does this by itself.

[quote user="alireza sadeghpour"]2) the slave device has two modes, connection, and pairing mode. in the connection mode, LE_General_Discoverable flag in the adverting data is false and in the pairing mode, LE_General_Discoverable flag in the advertising data is true.[/quote]

I am not sure I understand correctly. What do you mean with "slave doesn't respond to us"? You are not able to connect? Are you bonded?

[quote user="alireza sadeghpour"]3) can connection parameters like timeout or window size cause this problem?[/quote]

That is a wide question. The connection parameters can be quite complex, at least if you take the advertising parameters into account. But connection interval etc. should be fine, I guess.

[quote user="alireza sadeghpour"]4) in the trace, 5305.nrf52840_trace.pcapng you've seen that softdevice tries 6 time to send MTU and then terminates the connection. is there any way to increase 6 to 16 and then when slave dosen't respond softdevice terminates the connection?[/quote]

You can try to increase the connection supervision timeout, but I think we should focus on figuring out why the central sends these messages so soon, and doesn't behave more like the other sniffer trace. Do you know? Is there any way for me to reproduce this using one or more DKs? I suspect that your application is doing this on it's own, and before it should. It is not from the file that you sent in the previous reply. Perhaps you are calling something from your main.c file?

BR,
Edvin

RE: Softdevice couldn't initiate connection successfully

alireza sadeghpour — Mon, 01 Nov 2021 18:38:22 GMT

excuse me for the delay,

our MTU always was 517.

I've changed the MTU to 247, but it doesn't work again. (you can see it in the attached sniff log in packet 1277).

I've sme questoin:

1) what is the LL_FEATURE_REQ and is there any way to send that request with the soft device?

2) the slave device has two modes, connection, and pairing mode. in the connection mode, LE_General_Discoverable flag in the adverting data is false and in the pairing mode, LE_General_Discoverable flag in the advertising data is true.

in the pairing mode, we can connect and communicate with the device as expected (in the 5305.nrf52840_trace.pcapng trace packet 4981 you can see a connection established successfully).

do you see any point in that? when the LE_General_Discoverable is true everything works but when that flag is false slave doesn't respond to us.

3) can connection parameters like timeout or window size cause this problem?

4) in the trace, 5305.nrf52840_trace.pcapng you've seen that softdevice tries 6 time to send MTU and then terminates the connection. is there any way to increase 6 to 16 and then when slave dosen't respond softdevice terminates the connection?

thanks for your attention

devzone.nordicsemi.com/.../At-with-MTU.pcapng

RE: Softdevice couldn't initiate connection successfully

Edvin — Mon, 01 Nov 2021 13:47:50 GMT

What was the MTU size before you changed it, and was it working before you changed it? Can you try to set it to 247, does it work then?

RE: Softdevice couldn't initiate connection successfully

alireza sadeghpour — Mon, 01 Nov 2021 12:38:35 GMT

Thanks for your attention,

Yes, the central device is my nrf52850 and nrf52840_trace.pcapng is the sniffer trace when the connection hangs.
I can't change the peripheral side as it is a ready product from authentrend company.

Actually, I've just changed the NRF_SDH_BLE_GATT_MAX_MTU_SIZE to the 517 in the sdk_config.h and in the nrf_ble_gatt.c which is from the nordic SDK, in the on_connected_evt function, if the desired mtu was bigger than the effective mtu, calls the sd_ble_gattc_exchange_mtu_request function. in the attached file, in line 151 you can see this code snippet.

is it safe to remove this from the nrf_ble_gatt.c and call it manually?

devzone.nordicsemi.com/.../nrf_5F00_ble_5F00_gatt.c

sincerely

RE: Softdevice couldn't initiate connection successfully

Edvin — Mon, 01 Nov 2021 10:17:19 GMT

Hello,

So the central device in your nrf52840_trace.pcapng is the device you are working on, correct?

If so, how do did you call the MTU update on this device? Perhaps you can show some code snippets? I guess if you want this to be persistent across all devices, you can initiate it from the peripheral, if you are developing that one as well. If not, I suggest you look into having this in the connected event. If this is what you are doing already, perhaps you need to add a delay. I see from the sniffer trace that the central is asking for an MTU update immediately after the connection request, which seems a bit off. The peripheral didn't event respond to the connection request yet. Did you call it from the BLE_GAP_EVT_CONNECTED event?

Best regards,

Edvin