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From:   Emil Lenngren <emil.lenngren@gmail.com>
Date:   Mon, 26 Jul 2021 21:56:11 +0200
Message-ID: <CAO1O6se1=cHbH=VWyysVFJcumG=aGhquvKDs83CKfhrppzWEBg@mail.gmail.com>
Subject: Re: Instable BLE connection - MTU Request, Attribute not found
To:     =?UTF-8?Q?Peter_H=C3=B6ller?= <drmedvet.hoeller@gmail.com>,
        Bluez mailing list <linux-bluetooth@vger.kernel.org>
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Hi,

Den m=C3=A5n 26 juli 2021 kl 18:19 skrev Peter H=C3=B6ller <drmedvet.hoelle=
r@gmail.com>:
>
> Hi Emil!
>
> Thanks for your input!!
>
> I do have to stabilze this connection, I do not have any other chance,
> unfortunately.
>
> What I fell in my guts right now is that most likely:
>  this >>>>
> 2. The peripheral could use white listing to allow connections from
> only specific centrals. In this case the central will always see a
> connection complete immediately followed by a connection failed to be
> established.
> >>>>>
>
> and this>>>>>
> If the peripheral
> responds at least once, but after that at any time it doesn't respond
> to a central's packet within the set supervision timeout, the
> "Connection Timeout" disconnect reason will happen.
> >>>>>
>
> plays a role in my issue!!
>
> However , just to be mentioned, I cannot set (or prolong) supervision
> timeout period, which was my intention initially.
>
> here is what I am able to read/set (sudo nano) under:
> root@odroid:/sys/kernel/debug/bluetooth/hci0#
>
> 6lowpan                     force_sc_support         random_address
> adv_channel_map             force_static_address     rpa_timeout
> auto_accept_delay           hci_revision             sc_only_mode
> blacklist                   hci_version              sniff_max_interval
> conn_info_max_age           identity                 sniff_min_interval
> conn_info_min_age           identity_resolving_keys  ssp_debug_mode
> conn_max_interval           idle_timeout             static_address
> conn_min_interval           inquiry_cache            uuids
> dev_class                   le_auto_conn             voice_setting
> discov_interleaved_timeout  link_keys                white_list
> dut_mode                    long_term_keys           white_list_size
> features                    manufacturer
>
> Do you have any suggestions for those parameters or am I tuning on the
> wrong place here?
>
> However, I am going for wireshark fur ubuntu now, if I understood you rig=
ht?
>
> with kind regards
>
> Peter

Someone else should reply to the question about modifying the
supervision timeout. I think BlueZ hardcodes it but I might be wrong.
Either way you could always locate the code for it and recompile with
new parameters.

For a BLE sniffer you could for example use an nRF52 devkit, flash the
sniffer firmware at
https://www.nordicsemi.com/Products/Development-tools/nrf-sniffer-for-bluet=
ooth-le
and then use Wireshark to analyze the traffic in real time.

/Emil