[Interest] Problems with Qt 5.15.6 on windows when discovering details of a Bluetooth LE service

[Ivan Solovev]

Hi Michael,

I tried the 5.15.6 version with my BTLE device, and I can't reproduce it locally.
I see a peak on one core when I establish connection to the device and query all the services (my device has 14 services). But reading characteristics takes only about 50% of one core (one of the services has 9 characteristics, so it's comparable to your situation).

Recently we did some improvements and refactoring for the Bluetooth LE connection and service discovery process.
You can find some related changes in https://bugreports.qt.io/browse/QTBUG-80719, https://bugreports.qt.io/browse/QTBUG-83633 and https://bugreports.qt.io/browse/QTBUG-96057

You can try the latest patches and see if it improves the situation for you.

I'd also encourage you to create a simple non-gui application, just to eliminate the other CPU-consuming factors. It shouldn't be a problem, considering that you know your device's bluetooth address.

If you still see high CPU load, feel free to submit a bugreport, providing some more information about your hardware and the minimal reproducer.

Best regards,

Ivan Solovev
Senior Software Engineer

The Qt Company
Erich-Thilo-Str. 10 12489
Berlin, Germany

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Juha Varelius, Jouni Lintunen
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________________________________
From: Interest <interest-bounces at qt-project.org> on behalf of Michael Heiser | SYSTRONIK Elektronik und Systemtechnik GmbH <Heiser at systronik.de>
Sent: Thursday, October 7, 2021 7:46 AM
To: interest at qt-project.org <interest at qt-project.org>
Subject: [Interest] Problems with Qt 5.15.6 on windows when discovering details of a Bluetooth LE service


Hello Specialists,



I have problems regarding crashes or application hangs on windows 10
with QT 5.15.6 and Bluetooth LE and our own peripherals.

We have investigated this on old and also on
newer pc hardware. When doing a lowEnergyService discoverDetails() the CPU on
each core goes for seconds to 100% which could cause a deadlock in our app on
old hardware. On newer hardware the process of discoverDetails() goes often
good.
After the connect and the service discovery on our bluetooth peripheral with
lowenergyscanner when clicking on the service I can reproduce the high CPU
load. It needs about 5 seconds to query all the Characteristics of the
service, while querying the CPU load is that high on all cores.

By the way we have in this specifical BLE service 13 characteristics and
before reading the characteristics of this custom service we query
DeviceInformation service with 9 characteristics.

With Qt 5.12 the query of the same service of our peripheral was okay. So what
do you suggest to do?

I need to go on with Qt 5.15.6 because we have to launch a recent update on
Android within the same code base and I have already made the necessary
changes to QML files.

Android and IOS by the way are working super. Do you have any advice how to go
on? What I definitely not want is to have two source bases Qt 5.15.6 for
mobile and Qt 5.12.11 for Windows.

Mit freundlichen Grüßen  |  With best regards



Michael Heiser

Softwareentwicklung



Phone: +49 (0) 7558 / 9206-53

Email:   heiser at systronik.de<mailto:heiser at systronik.de>

Web:    www.systronik.com<http://www.systronik.com/>



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