QtSerialport blockingslave Example with Mainwindow class .

[Marco Flad]

i am using the blocking example to communicate with micro controller with Mainwindow class instead of dialog to send and receive data any time from micro-controller without block receiving data from GUI
so i redesign but this error is appear ,

ASSERT failure in QMutexLocker: "QMutex pointer is misaligned", file C:\Qt\5.13.1\mingw73_64\include\QtCore/qmutex.h, line 202
20:28:09: The program has unexpectedly finished.

---

//mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include "slavethread.h"
#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
private:
    Ui::MainWindow *ui;
    SlaveThread *m_thread ;
};
#endif // MAINWINDOW_H

---

//slavethread.h
#ifndef SLAVETHREAD_H
#define SLAVETHREAD_H

#include <QMutex>
#include <QThread>
#include <QWaitCondition>

class SlaveThread : public QThread
{
    Q_OBJECT
public:
    explicit SlaveThread(QObject *parent = nullptr);
    ~SlaveThread();
    void startSlave(const QString &portName, int waitTimeout, const QString &response);
signals:
    void request(const QString &s);
    void error(const QString &s);
    void timeout(const QString &s);

private:
    void run() override;

    QString m_portName;
    QString m_response;
    int m_waitTimeout = 0;
    QMutex m_mutex;
    bool m_quit = false;
};

#endif // SLAVETHREAD_H

---

//mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    m_thread->startSlave("COM15",10000,"HI");
}

MainWindow::~MainWindow()
{
    delete ui;
}

---

//slavethread.cpp
#include "slavethread.h"
#include <QSerialPort>
#include <QTime>
#include <QDebug>

SlaveThread::SlaveThread(QObject *parent) :
    QThread(parent)
{

}

SlaveThread::~SlaveThread()
{
    m_mutex.lock();
    m_quit = true;
    m_mutex.unlock();
    QThread::wait();
}

void SlaveThread::startSlave(const QString &portName, int waitTimeout, const QString &response)
{

    const QMutexLocker locker(&m_mutex);
    m_portName = portName;
    m_waitTimeout = waitTimeout;
    m_response = response;

    if (!QThread::isRunning())
        QThread::start();
}

void SlaveThread::run()
{
    bool currentPortNameChanged = false;

    m_mutex.lock();

    QString currentPortName;
    if (currentPortName != m_portName) {
        currentPortName = m_portName;
        currentPortNameChanged = true;
    }

    int currentWaitTimeout = m_waitTimeout;
    QString currentRespone = m_response;
    m_mutex.unlock();

    QSerialPort serial;

    while (!m_quit) {

        if (currentPortNameChanged) {
            serial.close();
            serial.setPortName(currentPortName);

            if (!serial.open(QIODevice::ReadWrite)) {
                emit error(tr("Can't open %1, error code %2")
                           .arg(m_portName).arg(serial.error()));
                return;
            }
        }

        if (serial.waitForReadyRead(currentWaitTimeout)) {

            // read request
            QByteArray requestData = serial.readAll();
            while (serial.waitForReadyRead(10))
                requestData += serial.readAll();

            // write response
            const QByteArray responseData = currentRespone.toUtf8();
            serial.write(responseData);
            if (serial.waitForBytesWritten(m_waitTimeout)) {
                const QString request = QString::fromUtf8(requestData);
                emit this->request(request);

            } else {
                emit timeout(tr("Wait write response timeout %1")
                             .arg(QTime::currentTime().toString()));
            }

            qDebug() << "Data :" <<  requestData;
           qDebug() << "Sent :" <<  responseData;

        } else {
            emit timeout(tr("Wait read request timeout %1")
                         .arg(QTime::currentTime().toString()));
        }

        m_mutex.lock();
        if (currentPortName != m_portName) {
            currentPortName = m_portName;
            currentPortNameChanged = true;
        } else {
            currentPortNameChanged = false;
        }
        currentWaitTimeout = m_waitTimeout;
        currentRespone = m_response;
        m_mutex.unlock();
    }
//! [13]
}

[kuzulis]

Don't use Qt 5.13.1, it has bugs.

[aha_1980]

@Marco-Flad Threading is an advanced topic.

Your problem can be solved with non-blocking serial communication, please use it and proper signal+slot handling.

Regards

[Marco Flad]

@aha_1980
the signal and slots dosnt work with readyread() dosn't triggered if data available on serial its only triggered when i send data from qt to the connected device"and this data is old data " i tried with no solution the issue is her if you can have a look please ,

https://forum.qt.io/topic/110038/qt-serial-port-not-receive-data-until-send-data-to-mc/5

[kuzulis]

Don't use Qt 5.13.1, it has bugs.

[aha_1980]

Hi @kuzulis,

Are those bugs fixed in 5.14.0 for sure?

Regards

[kuzulis]

I'm think, yes.