QSerialPort and QThread

[maratk1n]

Hi all!

I have a small project:

mainwindow.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    ComPort::get().open();
 
    thread = new QThread(this);
    connect(this, SIGNAL(destroyed(QObject*)), thread, SLOT(quit()));
 
    valve = new Valve(7);
    connect(valve, SIGNAL(remoteStatus(bool)), this, SLOT(remoteStatus(bool)));
 
    valve->moveToThread(thread);
 
 
    QTimer *valvesReadTimer = new QTimer(this);     
    connect(valvesReadTimer, SIGNAL(timeout()), valve, SLOT(getAllStates()));
    valvesReadTimer->start(1000);                   
 
    connect(passform, SIGNAL(manualModeEmit(bool)), 
            this, SLOT(manualMode(bool)));
 
 
    emergency = new EmergencyResetOfPressure();
    connect(emergency, SIGNAL(openValveSignal(int)), this, SLOT(openValve(int)));
    connect(emergency, SIGNAL(closeValveSignal(int)), this, SLOT(closeValve(int)));
    //emergency->start();
    emergency->moveToThread(emergency);
    emergency->start();
    thread->start();
 
    initActionConnection();
 
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::valveSwitch(int id)    //переключатель клапанов
{
    if (valve->getState(id))
        closeValve(id);
    else
        openValve(id);
}
 
void MainWindow::openValve(int id)
{
    QString str = "Клапан №" + QString::number(id+1);
    valveButton[id]->setEnabled(false);
    if (valve->open(id)) {
        if (manualModeState)
            valveButton[id]->setEnabled(true);
        //valveButton[id]->setPalette(QPalette(Qt::green));
        //valveButton[id]->setStyleSheet(VALVE_OPEN_COLOR);
        QString style = QString(DEFAULT_STYLE_BUTTON) + QString(DEFAULT_BACKGROUND_BUTTON);
        valveButton[id]->setStyleSheet(style);
        ui->mainLabel->setText(str + " открыл! :)");
    }
    else {
        if (manualModeState)
            valveButton[id]->setEnabled(true);
        ui->mainLabel->setText("Не могу открыть " + str);
        remoteStatus(0);
    }
}
void MainWindow::closeValve(int id)
{
    QString str = "Клапан №" + QString::number(id+1);
    valveButton[id]->setEnabled(false);
    if (valve->close(id)) {
        if (manualModeState)
            valveButton[id]->setEnabled(true);
        //valveButton[id]->setPalette(style()->standardPalette());
        valveButton[id]->setStyleSheet("");
        ui->mainLabel->setText(str + " закрыл! :)");
    }
    else {
        if (manualModeState)
            valveButton[id]->setEnabled(true);
        ui->mainLabel->setText("Не могу закрыть " + str);
        remoteStatus(0);
    }
}
 
void MainWindow::pressureDrop() //Испытание по методу "Спад давления"
{
    emergency->begin();
 
    ui->mainLabel->setText("Испытание по методу \n Спад давления");
}
 
 
void MainWindow::initActionConnection()
{
    //обработка нажатий на кнопки клапанов
    QSignalMapper* signalMapper = new QSignalMapper (this);     //чтобы можно было обработать ф-ю с аргументом в Слоте
    for(int i = 0; i < 7; i++)
        signalMapper->setMapping(valveButton[i], i);
    for(int i = 0; i < 7; i++)
        connect(valveButton[i], SIGNAL(clicked()), signalMapper, SLOT(map()));
    connect(signalMapper, SIGNAL(mapped(int)), this, SLOT(valveSwitch(int)));
 
 
    connect(ui->pressureTestButton, SIGNAL(clicked(bool)), this, SLOT(pressureDrop()));     //опрессовка и испытание на прочность
 
}
 
 
EmergencyResetOfPressure::EmergencyResetOfPressure(QObject *parent) : QThread(parent)
{
 
}
 
EmergencyResetOfPressure::~EmergencyResetOfPressure()
{
 
}
 
void EmergencyResetOfPressure::begin()
{
    for (int i = 0; i<7; i++)
    {
        //sleep(1);
        emit openValveSignal(i);
    }
    for (int i = 0; i<7; i++)
    {
        //sleep(1);
        emit closeValveSignal(i);
    }
}

File for working with valves and port (singleton class)

class ComPort : public QObject {    //класс синглтон
    Q_OBJECT
private:
    QString portName;
    QSerialPort *serial;
    explicit ComPort(QObject *parent = 0);
    ~ComPort();
 
    //защита от копирования
    ComPort(ComPort const&) = delete;
    ComPort& operator= (ComPort const&) = delete;
 
    int timeoutCount = 0;
    int responseCount = 0;
 
public:
    QByteArray buffer;
    static ComPort& get()
    {
        static ComPort instance;
        return instance;
    }
 
    void open();
    void close();
    QByteArray requestResponse(const QByteArray &data);
    void write(const QByteArray &data);
    bool crcCheck(const QByteArray &data);
private slots:
    void readData();
    void handleError(QSerialPort::SerialPortError error);
};

.cpp

Valve::Valve(int size, QObject *parent) : QObject(parent) //конструктор
{
    valveState.resize(size);
    for(int i = 0; i < size; i++)
    {
        valveState[i] = false;
    }
}
 
Valve::~Valve() //деструктор
{
 
}
 
bool Valve::open(int id)
{
    QByteArray arr;
    arr.resize(7);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x02;
    arr[3] = 0x02;
    arr[4] = id+1;
    arr[5] = 0xFF;
    arr[6] = 0x00 - arr[1] - arr[2] - arr[3] - arr[4] - arr[5];
 
    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        qDebug() << "клапан №: " << id+1 << " открыт!";
        valveState[id] = true;
 
        emit remoteStatus(1);
        return 1;
    }
 
    emit remoteStatus(0);
    return 0;
}
 
bool Valve::close(int id)
{
    QByteArray arr;
    arr.resize(7);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x02;
    arr[3] = 0x02;
    arr[4] = id+1;
    arr[5] = 0x00;
    arr[6] = 0x00 - arr[1] - arr[2] - arr[3] - arr[4] - arr[5];
 
    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        qDebug() << "клапан №: " << id+1 << " закрыт!";
        valveState[id] = false;
 
        emit remoteStatus(1);
        return 1;
    }
 
    emit remoteStatus(0);
    return 0;
}
 
/*****************************************
 *          Класс для работы с COM портом
 * **************************************/
 
ComPort::ComPort(QObject *parent) : QObject(parent)
{
    buffer = "";
    serial = new QSerialPort();
    connect(serial, SIGNAL(error(QSerialPort::SerialPortError)), this, SLOT(handleError(QSerialPort::SerialPortError)));
}
ComPort::~ComPort()
{
 
}
 
void ComPort::open()
{
    if(serial->isOpen())
        close();
    if(portName != Config::get().getValue("COM/name").toString())
    {
        qDebug() << "Порт " << portName << "сменился на " << Config::get().getValue("COM/name").toString();
        portName = Config::get().getValue("COM/name").toString();
    }
    serial->setPortName(portName);
    if (serial->open(QIODevice::ReadWrite)) {
        if (serial->setBaudRate(QSerialPort::Baud115200)
                && serial->setFlowControl(QSerialPort::NoFlowControl)) {
 
        qDebug() << "Порт открыт";
 
        } else {
            //QMessageBox::critical(this, "Error", serial->errorString());
            qDebug() << QString(serial->errorString());
            serial->close();
 
        }
    } else {
        //QMessageBox::critical(this, QObject::tr("Error"), serial->errorString());
 
    }
}
QByteArray ComPort::requestResponse(const QByteArray &data)
{
    QByteArray readBuf;
    qDebug() << "-------------------------";
    int attempts = 1;
    while (attempts <= REQATTEMPTS) {      //3 попытки
        if (serial->isWritable())
        {
            serial->write(data);
            qDebug() << "Попытка № " << attempts;
            qDebug() << "Запрос: " << data.toHex();
            while (serial->waitForReadyRead(WAITFORREADY)) {
                readBuf += serial->readAll();
                if (crcCheck(readBuf) && data[2] == readBuf[2] ){  //если CRC и команда сошлись -- успех!
                    qDebug() << "Ответ: " << readBuf.toHex();
                    responseCount++;
                    qDebug() << "Кол-во запросов:  " << responseCount;
                    qDebug() << "Кол-во таймаутов: " << timeoutCount;
                    float percent = timeoutCount * 100;
                    percent = percent / responseCount;
                    qDebug() << "Процент косяков:  " << QString::number(percent, 'f', 3) << "%";
                    close();
                    open();
                    return readBuf;
                }
            }
            readBuf.clear();
            qDebug() << "Таймаут...";
            timeoutCount++;
            close();
            open();
            attempts++;
        }
        else
        {
            qDebug() << "Порт " << portName << " не пишется!";
            return 0;
        }
 
    }
//    close();
//    open();
    return 0;
}
 
void ComPort::close()
{
    serial->close();
    qDebug() << "Порт закрыт";
}
void ComPort::write(const QByteArray &data)
{
    serial->write(data);
    qDebug() << "Запрос:        " << data.toHex();
}
void ComPort::readData()
{
    buffer = serial->readAll();
    if (ComPort::get().crcCheck(buffer))
    {
        qDebug() << "Ответ:         " << buffer.toHex();
        qDebug() << "---------------------------";
    }
}
void ComPort::handleError(QSerialPort::SerialPortError error)
{
    if (error == QSerialPort::ResourceError) {
        ComPort::get().close();
        qDebug() << "что-то не так!";
    }
}

While working, I get an error:

QObject: Cannot create children for a parent that is in a different thread.
(Parent is QSerialPort(0x197b7f8), parent's thread is QThread(0xc16e50), current thread is QThread(0x197c620)

How can I get rid of this error?
I hope for any help. Thanks!

[dheerendra]

Which function is supposed to be executed in thread ?. For me code looked as if no function is executed in thread. Also with error I feel it is coming from getallstates. Can you paste getallstates code ? U must be passing object created in one thread as parent to another object created another thread. Just for testing purpose can avoid passing parent while creating object ?

[maratk1n]

In the class of the main window, I create instances of classes of sensors, valves, etc. They are interrogated with a certain frequency by the timer. I want them to work in a separate thread so that the GUI does not hang.

getAllStates:

bool Valve::getAllStates()
{
    QByteArray arr;
    arr.resize(5);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x00;
    arr[3] = 0x00;
    arr[4] = 0x00 - arr[1] - arr[2] - arr[3];

    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        QBitArray bitStates(16);    //8 на клапана, 8 на фиттинги

        for (int i = 4; i<6; i++)   // конвертируем 4й и 5й байты (HEX) в биты (BIN)
            for (int b = 0; b<8; b++)
                bitStates.setBit((i-4)*8+b, response.at(i)&(1<<b));

        //qDebug() << bitStates;

        for (int i = 0; i < valveState.size(); i++)     //обновляем состояния клапанов
            valveState[i] = bitStates[i];
        for (uint i = 0; i < sizeof(fittingState); i++)  //обновляем состояния фиттингов
            fittingState[i] = bitStates[i+8];

        emit remoteStatus(1);
        return 1;
    }

    emit remoteStatus(0);
    return 0;
}

getAllStates is executed, for example, once per second. In the same thread, another function is executed with a frequency of three times per second:

bool PressureSensors::readSensors()
{
    QByteArray arr;
    arr.resize(5);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x03;
    arr[3] = 0x00;
    arr[4] = 0x00 - arr[1] - arr[2] - arr[3];

    QByteArray response = ComPort::get().requestResponse(arr);
    if(response[0] == arr[0])
    {
        QByteArray dd1 = response.mid(4, 2);
        QByteArray dd2 = response.mid(6, 2);
        QByteArray dd3 = response.mid(8, 2);
        QByteArray dd4 = response.mid(10, 4);
        pressureArray[3] = hexToFloat(reverseHex(dd4));
        float Pmax = 160.0;
        pressureArray[2] = hexToDec(reverseHex(dd3)) * Pmax / maxADC;
        pressureArray[1] = hexToDec(reverseHex(dd2)) * Pmax / maxADC;
        pressureArray[0] = hexToDec(reverseHex(dd1)) * Pmax / maxADC;

        emit remoteStatus(1);
        return 1;
    }

    emit remoteStatus(0);
    return 0;
}

[SGaist]

Hi,

Can you show the code where you do your thread handling ?

[kuzulis]

serial = new QSerialPort(this);

you have missed this, Luke!

PS: Don't use threads at all (if you don't know how to do it right)!

[J.Hilk]

There are some crucial parts of your valve-class missing to be sure, but I believe valve tries to access ther SerialPort created in your main thread ComPort::get().open(); form a different thread valve->moveToThread(thread);

@maratk1n said in QSerialPort and QThread:

ComPort::get().open();

thread = new QThread(this);
connect(this, SIGNAL(destroyed(QObject*)), thread, SLOT(quit()));

valve = new Valve(7);

connect(valve, SIGNAL(remoteStatus(bool)), this, SLOT(remoteStatus(bool)));

valve->moveToThread(thread);

That won't work, you'll need to create the port in the same thread it is accessed from or handle that via SIGNAL/SLOTS at all times.

[maratk1n]

@kuzulis said in QSerialPort and QThread:

serial = new QSerialPort(this);
you have missed this, Luke!

Tried it. Does not help.

@SGaist said in QSerialPort and QThread:

Can you show the code where you do your thread handling ?

What do you mean?..

@J.Hilk said in QSerialPort and QThread:

That won't work, you'll need to create the port in the same thread it is accessed from or handle that via SIGNAL/SLOTS at all times.

Redo the class methods in slots? But in fact the instance of the class QSerialPort will still be created in the main thread.

[jsulm]

@maratk1n said in QSerialPort and QThread:

What do you mean?..

The code where you create and start your threads.

"Redo the class methods in slots?" - do not create instance variables in the constructor of QThread derived classes! Such a class is created in the main thread - that means constructor is executed in the main thread and this means - everything created in the constructor is created in main thread. Create everything your thread needs in run() - run() is executed in that new thread.
See "It is important to remember that a QThread instance lives in the old thread that instantiated it, not in the new thread that calls run()." in http://doc.qt.io/qt-5.8/qthread.html
And take a look at https://mayaposch.wordpress.com/2011/11/01/how-to-really-truly-use-qthreads-the-full-explanation/

[maratk1n]

@jsulm said in QSerialPort and QThread:

The code where you create and start your threads.

This is written at the very beginning of the post, if I understood correctly

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    ComPort::get().open();
 
    thread = new QThread(this);
    connect(this, SIGNAL(destroyed(QObject*)), thread, SLOT(quit()));
 
    valve = new Valve(7);
    connect(valve, SIGNAL(remoteStatus(bool)), this, SLOT(remoteStatus(bool)));
 
    valve->moveToThread(thread);
 
 
    QTimer *valvesReadTimer = new QTimer(this);     
    connect(valvesReadTimer, SIGNAL(timeout()), valve, SLOT(getAllStates()));
    valvesReadTimer->start(1000);                   
 
    connect(passform, SIGNAL(manualModeEmit(bool)), 
            this, SLOT(manualMode(bool)));
 
 
    emergency = new EmergencyResetOfPressure();
    connect(emergency, SIGNAL(openValveSignal(int)), this, SLOT(openValve(int)));
    connect(emergency, SIGNAL(closeValveSignal(int)), this, SLOT(closeValve(int)));
    //emergency->start();
    emergency->moveToThread(emergency);
    emergency->start();
    thread->start();
 
    initActionConnection();
 
}

[maratk1n]

Has a little changed work with port:

bool Valve::getAllStates()
{
    QByteArray arr;
    arr.resize(5);
    arr[0] = 0xAB;
    arr[1] = 0x01;
    arr[2] = 0x00;
    arr[3] = 0x00;
    arr[4] = 0x00 - arr[1] - arr[2] - arr[3];

    emit requestResponse(arr);
//    QByteArray response = ComPort::get().requestResponse(arr);
//    if(response[0] == arr[0])
//    {
//        QBitArray bitStates(16);    //8 на клапана, 8 на фиттинги

//        for (int i = 4; i<6; i++)   // конвертируем 4й и 5й байты (HEX) в биты (BIN)
//            for (int b = 0; b<8; b++)
//                bitStates.setBit((i-4)*8+b, response.at(i)&(1<<b));

//        //qDebug() << bitStates;

//        for (int i = 0; i < valveState.size(); i++)     //обновляем состояния клапанов
//            valveState[i] = bitStates[i];
//        for (uint i = 0; i < sizeof(fittingState); i++)  //обновляем состояния фиттингов
//            fittingState[i] = bitStates[i+8];

//        emit remoteStatus(1);
//        return 1;
//    }

//    emit remoteStatus(0);
//    return 0;
}

And I configured the connection in the designer of the valve class:

connect(this, SIGNAL(requestResponse(QByteArray)), &ComPort::get(), SLOT(requestResponse(QByteArray)));

The error has disappeared

QObject: Cannot create children for a parent that is in a different thread.
(Parent is QSerialPort(0x197b7f8), parent's thread is QThread(0xc16e50), current thread is QThread(0x197c620)

But there were other problems:

1. The GUI is terribly slow.
2. The port class function is used by a variety of classes, so it is not clear to me how to determine which of them came the answer.