serial port programming in qt

[high_flyer]

So only i used Posix_QextSerialPort. Should i define somewhere about _TTY_POSIX ?

Exactly - You should add DEFINES += _TTY_POSIX in your pro file (or if you are using KDevelop it has a field for that in the qmake configuration).

[sar_van81]

high_flyer:

that parameter has already been set when i untar the qextserial package. should i specify that in my application pro file ?

Let me explain what i have done so far :

1). Downloaded the qextserial package , untarred and entered qmake ,make. there were the following libraries created:
libqextserialport.so libqextserialport.so.1 libqextserialport.so.1.0 libqextserialport.so.1.0.0

2). Then created a directory ,copied my source files. entered the header files and the libraries for qextserial in my project file. then entered make.

is this procedure correct ? else can you say me the correct one ?

[high_flyer]

should i specify that in my application pro file ?

yes.

is this procedure correct ? else can you say me the correct one ?

It should work.
But I would not copy the header files and libs, I would link to them or user the -L and -I in my make file.
But that is a subjective private taste matter, your way should work just as well.

[sar_van81]

hi ,

i specified in my project file also and it compiled successfully.but still the same error comes . Is there any permission i need to set to serial port ? i'l post my full code here if any one find any error please point me :

#include <qwidget.h>
#include <qapplication.h>
#include <stdlib.h>
 
#include <qextserialport.h>
 
class Widget : public QWidget
{
public:
    Widget( QWidget *parent=0, const char *name=0 );
private:
    int mouse;
    int mouseidx;
};
 
Widget::Widget( QWidget *parent, const char *name )
    : QWidget( parent, name)
{
    setMinimumSize(640,480 );
 
	QextSerialPort *note= new QextSerialPort("/dev/ttyS0");
	note->setBaudRate(BAUD115200);
	note->setParity(PAR_NONE);
	note->setDataBits(DATA_8);
	note->setStopBits(STOP_1);
	note->open(IO_ReadOnly);	
}
 
int main( int argc, char **argv )
{
    QApplication a( argc, argv );
    Widget connect1;
    a.setMainWidget( &connect1 );
    connect1.show();
    return a.exec();
}

#include <qwidget.h>
#include <qapplication.h>
#include <stdlib.h>

#include <qextserialport.h>

class Widget : public QWidget
{
public:
    Widget( QWidget *parent=0, const char *name=0 );
private:
    int mouse;
    int mouseidx;
};

Widget::Widget( QWidget *parent, const char *name )
    : QWidget( parent, name)
{
    setMinimumSize(640,480 );

	QextSerialPort *note= new QextSerialPort("/dev/ttyS0");
	note->setBaudRate(BAUD115200);
	note->setParity(PAR_NONE);
	note->setDataBits(DATA_8);
	note->setStopBits(STOP_1);
	note->open(IO_ReadOnly);	
}

int main( int argc, char **argv )
{
    QApplication a( argc, argv );
    Widget connect1;
    a.setMainWidget( &connect1 );
    connect1.show();
    return a.exec();
}

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[high_flyer]

compiled successfully.but still the same error comes .

I guess you mean the segmentation fault.

Your code has the following problems:

QextSerialPort *note= new QextSerialPort("/dev/ttyS0");

QextSerialPort *note= new QextSerialPort("/dev/ttyS0");

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You are allocating the serial port on to a local pointer.
You will not be able to access the serial port outside the constructor.
'note' needs to be a member variable.

Where is the code that handels the reading/writing to the serial port?

[sar_van81]

theLSB:
I did not add the read/write operation. i thougth first let me open the port sucessfuly. then,read that.

'note' needs to be a member variable

Do you mean that i need to declare it under protected and use it in the constructor ?

[high_flyer]

Do you mean that i need to declare it under protected and use it in the constructor ?

No, you need to declare it as a member variable.
Do you know what a member variable is?

class Widget : public QWidget
{
 private: //depends on your needs, this can be any access mode
  QextSerialPort *m_note;
public:
    Widget( QWidget *parent=0, const char *name=0 );
private:
    int mouse;
    int mouseidx;
};
 
Widget::Widget( QWidget *parent, const char *name )
    : QWidget( parent, name),
m_note(NULL)
{
    setMinimumSize(640,480 );
 
    m_note= new QextSerialPort("/dev/ttyS0");
   if(note)
   {
    m_note->setBaudRate(BAUD115200);
    m_note->setParity(PAR_NONE);
    m_note->setDataBits(DATA_8);
    m_note->setStopBits(STOP_1);
    m_note->open(IO_ReadOnly);   
   }
}

class Widget : public QWidget
{
 private: //depends on your needs, this can be any access mode
  QextSerialPort *m_note;
public:
    Widget( QWidget *parent=0, const char *name=0 );
private:
    int mouse;
    int mouseidx;
};
 
Widget::Widget( QWidget *parent, const char *name )
    : QWidget( parent, name),
m_note(NULL)
{
    setMinimumSize(640,480 );
 
    m_note= new QextSerialPort("/dev/ttyS0");
   if(note)
   {
    m_note->setBaudRate(BAUD115200);
    m_note->setParity(PAR_NONE);
    m_note->setDataBits(DATA_8);
    m_note->setStopBits(STOP_1);
    m_note->open(IO_ReadOnly);   
   }
}

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[sar_van81]

high_flyer:

yeah i did as you said. i tried both the ways-private or protected. But no use.

[high_flyer]

But no use.

Could you be a bit more descriptive?
The access mode has nothing to do with it.

[sar_van81]

first i tried declaring the Qextserialport as a private member variable, compiled and when i rum the same error came. next i tried declaring it as protected member variable, the same thing happened.

[high_flyer]

what error? segmentation falut?
Are there any other methods do the Widget class?
Try setting debug messages along the code or run in a debugger and see where the applciation crashes.

EIDT:
Wait, in the code I edited for you, your should change all 'note' instances to 'm_note' did you do that?

[sar_van81]

Hi,

i solved that problem. i did not declare it in the heap.The following is what i did:

QextSerialPort note("/dev/ttyS0");
note.setBaudRate(BAUD115200);
note.setParity(PAR_NONE);
note.setDataBits(DATA_8);
note.setStopBits(STOP_1);
note.open(IO_ReadOnly);

QextSerialPort note("/dev/ttyS0");
note.setBaudRate(BAUD115200);
note.setParity(PAR_NONE);
note.setDataBits(DATA_8);
note.setStopBits(STOP_1);
note.open(IO_ReadOnly);

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With this the application opens without segmentation fault. Now i'm finding out how to read the datas ? the suggestion b1 gave did not work out as there is no member function called read in the Qextserialport.

Anyway thanks a lot for all of your kind response .