[Interest] Bluetooth on Qt on Pi (for real this time)

[Jérôme Godbout]

here's a quick link for the feature exchange during pairing (OOB too like NFC):

http://blog.bluetooth.com/bluetooth-pairing-part-1-pairing-feature-exchange

https://blog.bluetooth.com/bluetooth-pairing-part-2-key-generation-methods

https://blog.bluetooth.com/bluetooth-pairing-passkey-entry?_ga=2.116852804.378017028.1515697544-664430033.1515094290

https://blog.bluetooth.com/bluetooth-pairing-part-4

https://blog.bluetooth.com/bluetooth-pairing-part-5-legacy-pairing-out-of-band


LL connection is the first step, from that point on, you can communicate with the device. Pairing are extra step to remember the device connections key in a relatively secure way (no bluetooth connection can be considered 100% bullet proof, but you can reduce the risk and the MIT attack).


  1.  connect
  2.  authentificate
  3.  encryption
  4.  GATT services discovery
  5.  Now you can exchange data

Also, make sure you understand this:
BLE 4.0 != BLE 4.2
4.0 is legacy / smart
4.2 is secure
Secure connection can only be acheive is both side support 4.2. Make sure you don't try to do it on 4.0 it won't be supported.

________________________________
From: Interest <interest-bounces+godboutj=amotus.ca at qt-project.org> on behalf of Jason H <jhihn at gmx.com>
Sent: June 29, 2018 9:33 AM
To: Maurice Kalinowski
Cc: Interest at qt-project.org
Subject: Re: [Interest] Bluetooth on Qt on Pi (for real this time)

Thanks all for your experience reports. Looking around, it seems that  disabling the built-in BT and going wth a dongle worked for some people. Has anyone tried that?

As for me bing a Bluetooth noob, what do I need to know about Bt vs TCP sockets? Speficically:
Can I access my service without pairing?
During pairing does my service have to be active?
Once paired, can I restart my service without having to re-pair?
Since my protocol is serial (Rfcomm) Do I have to use the existing serial Uuid?
How can I set the Pi to automatically pair with my application?

Many thanks!

Sent: Friday, June 29, 2018 at 3:44 AM
From: "Maurice Kalinowski" <Maurice.Kalinowski at qt.io>
To: "Tomasz Siekierda" <sierdzio at gmail.com>, "Shawn Rutledge" <Shawn.Rutledge at qt.io>
Cc: "Interest at qt-project.org" <interest at qt-project.org>
Subject: Re: [Interest] Bluetooth on Qt on Pi (for real this time)

>
> BT on Raspberry Pi is very unstable. I've tried to work with it 6 months ago and actually abandoned the project because it was practically unusable. However, I've noticed they have released a lot of software and firmware updates since then. So my first suggestion: upgrade Raspbian (if you are using it) to newest version.

Have they updated their Qt version yet?  Last time I tried Bluetooth on the Pi, a few months ago, they still had 5.7, which is ridiculous IMO.  I wanted to try BLE, so had to recompile Qt on the Pi.  And yeah, BT wasn’t stable either.



I don't think so, Raspbian usually sticks to the same Qt version for whole release cycle. So, last Raspbian had Qt 5.2, this one has 5.7 and that's it. I haven't checked recently, though, I always compile my own anyway.



[Maurice Kalinowski]

On the SensorTag demo we did for Qt for Automation we also recognized a heavy instability of BT on the Pi. Basically on every third boot “rfkill unblock” and “hciconfig” are your weapons. It’s hard to automate this, but that might be somewhat of an option for prototyping. Basically you need to restart the whole BT stack after a boot a second time.



Maurice



P.S.:Please forgive my Outlook reply-for format.

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