serial port communication

[robotics]

hello everybody
I am using qt in window. I am trying to communicate with my serial port device. I have already downloaded the "QExtSerialPort" and Sucessfullly build it.
I want to receive the data sent my my hardware devices in my Gui application..for simple I want just to recieve data from serial port ...........please can anyone share example with me......ur help shall be highly appreciated

[squidge]

QExtSerialPort comes with lots of examples already...

[robotics]

I have managed to open the serial port . Since I am sending characters continiously from micrcontroller and I am recieving garbage data in my gui....
please help me::
my code is as follow::
I should recieve data when I press the button .........but I am recieving garbage value in my lineEdit..

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "qextserialport.h"
#include "qdebug.h"
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::on_pushButton_clicked()
{
       QextSerialPort * port = new QextSerialPort();
       port->setPortName("COM4");
       port->setBaudRate(BAUD9600);
       port->setFlowControl(FLOW_HARDWARE);
       port->setParity(PAR_NONE);
       port->setDataBits(DATA_8);
       port->setStopBits(STOP_1);
       port->open( QIODevice::ReadOnly );
       char *buff;
       if(port->isReadable())
       {
       qint64 i=port->read(buff,1);
       buff[i]='\0';
       if(i!=-1)
       {
       QString str(buff);
       ui->lineEdit->setText(str);
       port->close();
   }
   }
 
   else
       qDebug("port not open");
}

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "qextserialport.h"
#include "qdebug.h"
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

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

void MainWindow::on_pushButton_clicked()
{
       QextSerialPort * port = new QextSerialPort();
       port->setPortName("COM4");
       port->setBaudRate(BAUD9600);
       port->setFlowControl(FLOW_HARDWARE);
       port->setParity(PAR_NONE);
       port->setDataBits(DATA_8);
       port->setStopBits(STOP_1);
       port->open( QIODevice::ReadOnly );
       char *buff;
       if(port->isReadable())
       {
       qint64 i=port->read(buff,1);
       buff[i]='\0';
       if(i!=-1)
       {
       QString str(buff);
       ui->lineEdit->setText(str);
       port->close();
   }
   }

   else
       qDebug("port not open");
}

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[high_flyer]

your 'buff' is not initialized!!
And since you always only read one char, why do you use a pointer and not just a char?

[squidge]

You should also be using signals and slots.

I assume your micro is sending just text? Because thats all a lineedit can display.

[robotics]

guys thanks for your reply
actually my microcontroller sends character continiously everytime(i.e. sends character 'a'continiously)
I used it just to check whether my gui is recieving or not ....
but still I am recieving garbage value in lineedit
I modified according to your suggestion
I used Qtimer that operates on overy 0.5 secs
My CODE

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "qextserialport.h"
#include "qdebug.h"
#include "qtimer.h"
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QTimer *timer=new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(timeupdate()));
    timer->start(500);
//    QextSerialPort * serialport=new QextSerialPort;
//    connect(serialport,SIGNAL(readyRead()),this,SLOT(timeupdate()));
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
 
void MainWindow::timeupdate()
{
    QextSerialPort * port = new QextSerialPort();
    port->setPortName("COM4");
    port->setBaudRate(BAUD9600);
    port->setFlowControl(FLOW_HARDWARE);
    port->setParity(PAR_NONE);
    port->setDataBits(DATA_8);
    port->setStopBits(STOP_1);
    //port->setTimeout(0);
    port->open( QIODevice::ReadOnly );
    char buff[4];
    if(port->isReadable())
    {
    qint64 i=port->read(buff,1);
    buff[i]='\0';
    if(i!=-1)
    {
    QString str(buff);
    ui->lineEdit->setText(str);
    port->close();
}
}
 
else
    qDebug("port not open");
}

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "qextserialport.h"
#include "qdebug.h"
#include "qtimer.h"
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QTimer *timer=new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(timeupdate()));
    timer->start(500);
//    QextSerialPort * serialport=new QextSerialPort;
//    connect(serialport,SIGNAL(readyRead()),this,SLOT(timeupdate()));
}

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


void MainWindow::timeupdate()
{
    QextSerialPort * port = new QextSerialPort();
    port->setPortName("COM4");
    port->setBaudRate(BAUD9600);
    port->setFlowControl(FLOW_HARDWARE);
    port->setParity(PAR_NONE);
    port->setDataBits(DATA_8);
    port->setStopBits(STOP_1);
    //port->setTimeout(0);
    port->open( QIODevice::ReadOnly );
    char buff[4];
    if(port->isReadable())
    {
    qint64 i=port->read(buff,1);
    buff[i]='\0';
    if(i!=-1)
    {
    QString str(buff);
    ui->lineEdit->setText(str);
    port->close();
}
}

else
    qDebug("port not open");
}

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and In mainwindow.h

#include <QMainWindow>
 
namespace Ui {
    class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
private:
    Ui::MainWindow *ui;
 
private slots:
 
    void timeupdate();
};

#include <QMainWindow>

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow *ui;

private slots:
    
    void timeupdate();
};

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[Lesiok]

Why are You opening and closing port again and again ?????
Open port in MainWindow constructor and close it in destructor.

[serjts]

I remeber making a working program and I started with the examples.. check those first

[squidge]

Even worse, every 500ms you are creating a new QextSerialPort but never deleting it

Are you sure all the parameters are correct? You are using hardware flow control and 9600 baud?

Check the output from your micro with a DSO to confirm its sending what you think its sending and dont forget the common fault of forgetting the level translator between the micro and PC.

[robotics]

Why are You opening and closing port again and again ?????
Open port in MainWindow constructor and close it in destructor.

I tried as You suggested but my program does not run....instead it gets hang
please help me to modify the above code........It's really frustrating me...

Are you sure all the parameters are correct? You are using hardware flow control and 9600 baud?

Check the output from your micro with a DSO to confirm its sending what you think its sending and dont forget the common fault of forgetting the level translator between the micro and PC.

yes I have checked that my microcontroller is sending the data...
please help me...

[squidge]

So everything works correctly if you use a terminal program such as Hyperterm?