@SpaceToon said in Unknown Exception is not beeing caught in trycatch-Block (Bluetooth Low Energy, ServiceDetailsDiscovery):

@KH-219Design : Thank you very much for your suggestion, for using the lowenergy example from Qt. I did this and the same error occurs there! For this reason, I copied the following code from there and paste it in my .cpp file

@SpaceToon I'm truly happy to hear you are able to make forward progress on this!

This year marks the first year that I have ventured into BLE using Qt, and I have hit some minor hiccups myself. That is why your post caught my attention in the first place. However, I am working on Android and you are on Windows, which have very different backend/underlying BLE system stacks. So based on the difference in operating systems, I was doubtful if anything I learned would really translate directly here.

Your watershed moment about QLowEnergyController::Error prompted me to go look at my code again to see what I am doing in case of QLowEnergyController::Error. I noticed that in my slot I have this comment:

// The Qt API for QLowEnergyController has some confusing // overlap/ambiguity. When we get "ConnectionError" I would EXPECT that // the signal QLowEnergyController::disconnected would also be // forthcoming. But it seems (by observation) that this is not how it // works. So we have to treat BOTH the disconnected signal and the // error signal as signs of a disconnection.

... so maybe you and I did actually run into a very similar pitfall after all!

It would be great to know if there is some null-reference bug in Qt BLE itself, but neither you nor I may have time to investigate that further. Since we both seem to have worked around our respective pain points, may we carry on and each deliver a successful project!

You also asked:

Did you compile Qt for debug, and can the debugger see/know the location of the corresponding Qt source files?

Which is a very useful tactic, which I have done many times on Linux Qt.

I just read some of this: https://stackoverflow.com/questions/5571098/how-can-i-make-msvc-debugger-step-into-qt-library-source-code-again/5576414

Which refers to compiling the QtCored5.dll DLL(s) for oneself. (This is essentially analogous to how I do it on Linux, but building Qt from source is usually several hours of effort on the first time... and I'm not talking about the additional potential hours of just letting the compiler run!)

Maybe someone else in this thread has had personal experience with debugging into Qt source files on Microsoft Windows. Or maybe that could be a new thread!

See https://bugreports.qt.io/browse/QTBUG-86095 for further informations

I have exactly the same problem see my topic. Actually I did not find any solution

@mrjj said in Writing to the file continuously in Qt (realtime data)?:

@SpaceToon
hi
Yes you just want to open it once.
But i dont see you calling flush anywhere ?

Oh, I forgot to paste the flush here, it is actually in my code directly after the write-statement. Thank you very much :)

Okay, I have solved the problem with a workaround: In the code for my development board I added a new line character after every value.
Then, in my Qt code I check every time the SLOT is called if the value does have a new line char.
Either the value is saved in another variable until it receives a value with a new line character or it is output immediately (if it has a new line character).

static QString newValue= ""; void MainWindow::updateData(const QLowEnergyCharacteristic &c,const QByteArray &value) { newValue = newValue + (QString)value; if (newValue.contains("\n") || newValue.contains("\r")){ ui->dataList->addItem(newValue.simplified()); ui->dataList->scrollToBottom(); newValue = ""; } }

Thank you both very much.

Thank you for your reply. I found this in the documentation:

In some cases the peripheral generates value updates which the central is interested in receiving. In order for a characteristic to support such notifications it must have the QLowEnergyCharacteristic::Notify or QLowEnergyCharacteristic::Indicate property and a descriptor of type QBluetoothUuid::ClientCharacteristicConfiguration. Provided those conditions are fulfilled notifications can be enabled as shown in the following code segment:

QLowEnergyCharacteristic batteryLevel = service->characteristic( QBluetoothUuid::BatteryLevel); if (!batteryLevel.isValid()) return; QLowEnergyDescriptor notification = batteryLevel.descriptor( QBluetoothUuid::ClientCharacteristicConfiguration); if (!notification.isValid()) return; // establish hook into notifications connect(service, SIGNAL(characteristicChanged(QLowEnergyCharacteristic,QByteArray)), this, SLOT(characteristicChanged(QLowEnergyCharacteristic,QByteArray))); // enable notification service->writeDescriptor(notification, QByteArray::fromHex("0100"));

So you were right. But what I do not understand: The writeDescriptor function "Writes newValue as value for descriptor." But what "value" is the QByteArray::fromHex("0100") ? Because when i write the same code for my application and when I call value() on the ClientCharacteristicConfiguration Descriptor from my RX characteristic the output is \x00\x00

Ah ok sorry! Indeed last time I worked with BT it was with older Qt version.

@TUStudi

AFAIK writing an MS Excel file is not possible with Qt directly. You need some additional stuff.
But writing to a file in general (raw textfile, JSON, XML... etc) is quite easy.

The QTBluetooth Central API is not supported on any platform.
see the first table in Qt Bluetooth

i had same error in my project.
this page helped me -> https://forum.qt.io/topic/117241/why-qlowenergyservice-unknownerror/2

i have changed my code from

connect(controller, &QLowEnergyController::discoveryFinished, this, &Device::serviceScanDone);

to

connect(controller, &QLowEnergyController::discoveryFinished, this, &Device::serviceScanDone,Qt::QueuedConnection);

and problem disappeared.

@martial123 These dongles are needed, if you use the node.js Bluetooth Low Energy library called "noble" (this video is actually about how to use noble), I only linked it because he also explains how to use Zadig. I don't know if your Dongle, that you have know, will work with Qt BluetoothLE library, just try it, if not, you could then try one of these listed in the video .

Thank you very much for your reply.

@sierdzio said in Bluetooth LE performance in different platforms:

Is the simulated beacon paired in Windows Bluetooth settings? Without it, Qt will not detect it! (this will be fixed in Qt 5.14 I think).,

Unfortunately, Windows does not allow me to pair the simulated iBeacon since it does not appear in the available Bluetooth devices list from the control panel.

@sierdzio said in Bluetooth LE performance in different platforms:

Also, make sure you're using the newest Windows version with all updates. Unfortunately, Bluetooth support on Windows is quite bad, has memory leaks etc. In early Windows 10 builds it was barely working at all.

Sure, it is the latest Windows version with all updates.

I was also trying to compile the Qt 5.15 source available in the repo to enable the win32 Bluetooth API to see if it makes any difference but I wasn't able to compile it... But this was just a curiosity. For me it's OK to consider Windows as the least compatible platform for the moment.

About Android, I was able to tune the application and now it can properly detect the simulated iBeacon. I was using the Bluetooth LE scanner example but I hadn't checked the manifest file so that was probably the issue.

@SpaceToon said in Dummy backend running. Qt Bluetooth module is non-functional (Bluetooth Low Energy):

So is it possible with the MSVC Compiler?

No.
You will need to build your code for Linux. It is better to do this on a Linux machine as cross compiling from Windows to Linux will be a lot of work. You can have a virtual machine with Linux to build for Linux.