Hi,

In addition to @Pl45m4, you don't print any information if the opening of the serial port failed. Doing that will help track the issue.

@Christian-Ehrlicher Yup, it worked! Thanks a lot.

@jsulm Yes i know. Thank you for answering.

Sounds like you should not be using QSerial and instead design a custom solution outside of Qt. Qt is not for real-time processing and your description of the task seems to imply real-time constraints.

@J-Hilk

A colleague of mine tried the 5.12.4, but the error is still there. I'll try with the QQuickPaintedItem or I'll switch to the 5.14.

Thanks for your time.

@kuzulis I've had a look at socat, and that looks to work! I now have a small example where I can write/read from a serial port. On the other end I am using screen, and my program picks up data as expected!

Thanks for the pointer to socat! Didn't know about it..

Thanks for the answers, I found the connection problem. I added the part:

void MainWindow::on_connectType_currentIndexChanged(int index)
{
if (modbusDevice) {
modbusDevice->disconnectDevice();
delete modbusDevice;
modbusDevice = nullptr;
}

auto type = static_cast<ModbusConnection> (index); if (type == Serial) { modbusDevice = new QModbusRtuSerialMaster(this); } else if (type == Tcp) { modbusDevice = new QModbusTcpClient(this); if (ui->portEdit->text().isEmpty()) ui->portEdit->setText(QLatin1Literal("127.0.0.1:502")); } connect(modbusDevice, &QModbusClient::errorOccurred, [this](QModbusDevice::Error) { statusBar()->showMessage(modbusDevice->errorString(), 5000); }); if (!modbusDevice) { ui->connectButton->setDisabled(true); if (type == Serial) statusBar()->showMessage(tr("Could not create Modbus master."), 5000); else statusBar()->showMessage(tr("Could not create Modbus client."), 5000); } else { connect(modbusDevice, &QModbusClient::stateChanged, this, &MainWindow::onStateChanged); }

}

And now I can make a connection.

Now I have to test it on the device, but i can't access it for a while, to be continued

Hi @Mark81

Can you share the settings of your serial port?
Are you sure about them ? Is Flow Control enabled?

@mrjj
no, a callback is just the nomenclature you use to describe functions passed as arguments to other functions to be invoked later.

@Aras said in Help me write my first QML wrapper for a C++ class:

I think you are right about this and the problem is that the line above is not executed. There is a problem though: I am using application manager, so my application does not have the conventional main function. I have am declaring ApplicationManagerWindow in QML and starting my application using appman command. I looked at the application manager docs but I could not find anything there. Do you know how I could make this C++ call if I am using appman?

In that case, the registration needs to be done in a plugin.
http://doc.qt.io/qt-5/qtqml-modules-cppplugins.html covers the process.

Hi @Aras
I would maybe post to the interest mailing ( http://lists.qt-project.org/mailman/listinfo/interest ) list and ask around.
With the Qt Automotive work happening, there might be someone else also thinking of CanBus and QML.

@Wieland Well i found my problem, I chose the wrong baudrate. Now i have to adjust my code, but i think it will work sooner or later. Thanks again!

@Wuzi said:
QStrings do not use \0 as end of string marker , as far as i know
but will put one there when converted to std string etc.
QbyteArray can also include the \0
please see
http://doc.qt.io/qt-5/qbytearray.html#data

I solved this.
I moved everything related to the serial port into a separate class SerialWorker and moved it to a separate thread.

QThread* serialthread = new QThread; SerialWorker* serialworker = new SerialWorker(); serialworker->moveToThread(serialthread); connect(serialthread, SIGNAL(started()), serialworker, SLOT(InitSerialPort())); serialthread->start(); connect(serialworker, SIGNAL(NewProto(QByteArray)), this, SLOT(ProtocolInterpreter(QByteArray))); connect(this, SIGNAL(SendRS(QByteArray)) , serialworker, SLOT(writeData(QByteArray)));

This works as supposed. Serial port is now more or less very responsive.
WebKit is still blocking the GUI thread sometimes but thats not as much an issue as the serial port not responding.

Hi and welcome to devnet,

Why the double conversion to stdString and c_str ? You can use something like toLatin1 if you want a QByteArray to write to your serial port.

Use QtSerialPort instead (branch qt4-dev): http://code.qt.io/cgit/qt/qtserialport.git/?h=qt4-dev
Wiki: https://wiki.qt.io/Qt_Serial_Port

PS: Also you can install QtSerialPort from the Fedora's repo

Sorry, I misunderstood your problem. You don't need to keep all the data in-memory, you can read the file update the xml and write it again.

On the other hand, you could also use a simple sqlite database to store your values and generate the xml only when needed.

You're welcome !

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