Re: Problems reading characteristics with Bluez 5.52

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Hi Peter,

On Thu, Jan 2, 2020 at 5:58 PM Peter Belau <pbelau1@xxxxxxxxx> wrote:
>
> Thank you very much for the response;  I did not realize that
> 'indicate' was exclusive to doing an attribute read. However, "notify
> on" doesn't seem to help. The device disconnects after a read and now
> I can no longer connect to it at all:
>
> QardioARM:/service0400/char0410]# notify on
> Notify started
> [CHG] Device 5C:D6:1F:0E:0A:7D ServicesResolved: no
> [CHG] Device 5C:D6:1F:0E:0A:7D Connected: no
>
> [bluetooth]#  connect 5C:D6:1F:0E:0A:7D
>
>
> Attempting to connect to 5C:D6:1F:0E:0A:7D
> Failed to connect: org.bluez.Error.Failed
>
>
> On the bluetoothd side I'm seeing:
>
> bluetoothd[20426]: src/agent.c:agent_disconnect() Agent :1.626 disconnected
> bluetoothd[20426]: src/agent.c:remove_default_agent() Default agent cleared
> bluetoothd[20426]: src/adapter.c:set_mode() sending set mode command for index 0
> bluetoothd[20426]: src/agent.c:agent_destroy() agent :1.626
> bluetoothd[20426]: src/agent.c:agent_unref() 0x55e718787df0: ref=0
> bluetoothd[20426]: src/adapter.c:new_settings_callback() Settings: 0x00000a01
> bluetoothd[20426]: src/adapter.c:settings_changed() Changed settings: 0x00000010
> bluetoothd[20426]: src/adapter.c:settings_changed() Pending settings: 0x00000000
> bluetoothd[20426]: src/agent.c:add_default_agent() Default agent set
> to :1.627 /org/bluez/agent
> bluetoothd[20426]: src/adapter.c:set_mode() sending set mode command for index 0
> bluetoothd[20426]: src/agent.c:agent_ref() 0x55e7187b7a00: ref=1
> bluetoothd[20426]: src/agent.c:register_agent() agent :1.627
> bluetoothd[20426]: src/adapter.c:new_settings_callback() Settings: 0x00000a11
> bluetoothd[20426]: src/adapter.c:settings_changed() Changed settings: 0x00000010
> bluetoothd[20426]: src/adapter.c:settings_changed() Pending settings: 0x00000000
> bluetoothd[20426]: src/device.c:att_connect_cb() connect error:
> Connection refused (111)
>
> I should note that I've tried a number of BTLE blood pressure devices
> with a variety of BT controllers and Bluez cannot seem to maintain
> reliable connections with any of the configurations I've tried. Any
> help would be much appreciated.

HCI trace would probably help here, you can collect it using btmon.
Have you check the spec if there are other steps before subscribing?

> On Thu, Jan 2, 2020 at 7:30 PM Luiz Augusto von Dentz
> <luiz.dentz@xxxxxxxxx> wrote:
> >
> > Hi Peter,
> >
> > On Thu, Jan 2, 2020 at 5:22 PM Peter Belau <pbelau1@xxxxxxxxx> wrote:
> > >
> > > I'm trying to get a Qardio ARM BP monitor working with Linux/Bluez but
> > > cannot seem to read any device characteristics with Bluez. My
> > > interaction through bluetoothctl looks like this:
> > >
> > > # menu gatt
> > > # attribute-info  00002a35-0000-1000-8000-00805f9b34fb
> > > Characteristic - Blood Pressure Measurement
> > >     UUID: 00002a35-0000-1000-8000-00805f9b34fb
> > >     Service: /org/bluez/hci0/dev_B0_49_5F_02_B5_61/service0400
> > >     Value:
> > >   16 7f 00 49 00 5b 00 00 00 00 00 00 00 00 35 00  ...I.[........5.
> > >   00 00                                            ..
> > >     Notifying: no
> > >     Flags: indicate
> > > # select-attribute 00002a35-0000-1000-8000-00805f9b34fb
> > > # read
> > > # Attempting to read /org/bluez/hci0/dev_B0_49_5F_02_B5_61/service0400/char0410
> > > Failed to read: org.bluez.Error.Failed
> > >
> > > I have bluetoothd running with debug flags but nothing appears in the
> > > debug logs. What am I doing wrong?
> >
> > Look at the flags, it only has indicate so it doesn't support reading directly.
> >
> > --
> > Luiz Augusto von Dentz



-- 
Luiz Augusto von Dentz



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