read and write in serial port

neda

Hi
I'm using Qt version 5.5.1 from windows 8.1.
I create a Qt Quick Controls Application.
Port opens, but I can not read data.
I have a error:
"Break condition detected while reading" (Error code 6)
Please guide me.

main.cpp:

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QtSerialPort/QtSerialPort>
#include <myserialport.h>
#include <mythread.h>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    //MySerialPort();
    MySerialPort iSerialPort;
    iSerialPort.openSerialPort();

    return app.exec();
}

myserialport.cpp:

#include "myserialport.h"
#include <QtSerialPort/QSerialPort>
#include <QMessageBox>
#include <QObject>

MySerialPort::MySerialPort()
{
    serial = new QSerialPort(this);
    connect(serial, SIGNAL(readyRead()), this, SLOT(readData()));
    //openSerialPort();
}


void MySerialPort::openSerialPort()
{
    serial->setPortName("COM3");
    serial->setBaudRate(QSerialPort::Baud9600);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity(QSerialPort::NoParity);
    serial->setStopBits(QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::NoFlowControl);
    if (serial->open(QIODevice::ReadWrite)) {

        showStatusMessage("Connectedd");

    } else {

        showStatusMessage(tr("Open error"));
    }
}

void MySerialPort::closeSerialPort()
{
    if (serial->isOpen())
        serial->close();

    showStatusMessage(tr("Disconnected"));
}

void MySerialPort::writeData(const QByteArray &data)
{
    serial->write(data);
}

void MySerialPort::readData()
{
   QByteArray data = serial->readAll();

   qDebug() << data;

}

void MySerialPort::handleError(QSerialPort::SerialPortError error)
{
    if (error == QSerialPort::ResourceError) {
        closeSerialPort();
    }
}


void MySerialPort::showStatusMessage(const QString &message)
{
    qDebug() << message;
}

myserialport.h:

#ifndef MYSERIALPORT_H
#define MYSERIALPORT_H
#include <QtSerialPort/QtSerialPort>
#include <QObject>

class MySerialPort: public QSerialPort
{
     Q_OBJECT
public:
    MySerialPort();

public slots:
    void openSerialPort();
    void closeSerialPort();

    void writeData(const QByteArray &data);
    void readData();

    void handleError(QSerialPort::SerialPortError error);

private:
    void showStatusMessage(const QString &message);

    QSerialPort *serial;

};

#endif // MYSERIALPORT_H

myproject.pro:

TEMPLATE = app

QT += qml quick widgets
QT += serialport

SOURCES += main.cpp \
    myserialport.cpp \
    mythread.cpp

RESOURCES += qml.qrc

# Additional import path used to resolve QML modules in Qt Creator's code model
QML_IMPORT_PATH =

# Default rules for deployment.
include(deployment.pri)

HEADERS += \
    myserialport.h \
    mythread.h

SGaist

Hi,

Do you have any other application also accessing that serial port ?

neda

@SGaist

Hi,
I read data with Hercules_3-2-6 Application (rs232 terminal software), but before opening my program, I closed Hercules_3-2-6 Application

neda

My program worked today, and I have not any error.
But I do not any change to program.

When I run program,
program connects to port successfully, but I receive just one data (space).

But when I close this program and open Hercules_3-2-6 Application (rs232 terminal software), that application read data,
and after close Hercules_3-2-6 application and open my application again, this program works and reads data until restarting computer.

I repeat this process many times.

But my project does not receive data after restarting system until port opens one time by Hercules_3-2-6 Application.

Meanwhile I have virtual USB COM port and my hardware connected to computer with USB.

SGaist

Are you using the same serial port setup in both your application and Hercules_3-2-6 ?

neda

@SGaist

yes, I using the same serial port setup in both my application and Hercules_3-2-6 .

Specification of port: Name: COM3, Baud Rate: 9600, Data bits: 8, Parity: None, Stop bits: 1, Flow control: None

Hercules_3-2-6

My program:

void MySerialPort::openSerialPort()
{
    serial->setPortName("COM3");


    if (serial->open(QIODevice::ReadWrite)) {
        serial->setParity(QSerialPort::NoParity);
        serial->setBaudRate(QSerialPort::Baud9600);
        serial->setDataBits(QSerialPort::Data8);
        serial->setStopBits(QSerialPort::OneStop);
        serial->setFlowControl(QSerialPort::NoFlowControl);
        showStatusMessage("Connectedd");

    } else {

        showStatusMessage(tr("Open error"));
    }
}

Meanwhile I have the same problem in qtserialport terminal example.
When I run qtserialport terminal example, program connects to port successfully, but does not receive any data.
But when I close this program and open Hercules_3-2-6 Application (rs232 terminal software), that application read data, and after close Hercules_3-2-6 application and open terminal example again, this program works and reads data until restarting computer.

SGaist

Does the device need DTR ?

neda

No,
I wrote a C# .net program. It worked very well likes to Hercules_3-2-6 Application and qt program worked after opening the program.
I added this line for handle error port.

void MySerialPort::handleError(QSerialPort::SerialPortError error)
{
    qDebug() << "Error: " << error;//I added this line

    if (error == QSerialPort::ResourceError) {
        showStatusMessage(serial->errorString());
        closeSerialPort();
    }
}

Result of run program:

Error: 0
"Connectedd"
Error: 6
"\x00"

Just sometimes I have error 6.
How do I fix break condition error?

SGaist

@kuzulis might have an idea about that one

neda

This post is deleted!

neda

@SGaist
Thank you very much my dear.
Your answer was a big help for me.

My problem was solved by set "setDataTerminalReady" function to false.
I did not have information about the signal DTR, by pointing you I read about that and find my problem.

TobyBar

This post is deleted!

asterixxx

https://www.youtube.com/watch?v=7ny6Hrdc_2M&t=47s