serial port programming in qt

[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 .

[high_flyer]

What you did is no good.
The serial port gets created on the stack, and dies when the constructor ends.
Use the code I gave you.

[sar_van81]

high_flyer:

Oops. it still not working. This is my code:

ConnectWidget::ConnectWidget( QWidget *parent, const char *name )
: QWidget( parent, name),m_note(NULL)
{
setBackgroundColor( white );
setMinimumSize(640,480 );

m_note= new QextSerialPort("/dev/ttyS0");
if(m_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);
}
printf("\n serial port openned \n");
}

Is this what you suggested?

[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.

And please use code tags.

[sar_van81]

Sir,

I modified the code. Now i have onely three lines in my code:

class ConnectWidget : public QWidget
{
public:
    ConnectWidget( QWidget *parent=0, const char *name=0 );
private:
    QextSerialPort *m_note;
};
ConnectWidget::ConnectWidget( QWidget *parent, const char *name )
    : QWidget( parent, name),m_note(NULL)
{
       	setMinimumSize(640,480 );
	m_note= new QextSerialPort("/dev/ttyS0");
	printf("\n serialport openned \n");
}

class ConnectWidget : public QWidget
{
public:
    ConnectWidget( QWidget *parent=0, const char *name=0 );
private:
    QextSerialPort *m_note;
};
ConnectWidget::ConnectWidget( QWidget *parent, const char *name )
    : QWidget( parent, name),m_note(NULL)
{
       	setMinimumSize(640,480 );
	m_note= new QextSerialPort("/dev/ttyS0");
	printf("\n serialport openned \n");
}

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I have not added the settings of the serial port.As i found that starting from this line the error pops up. the following is the error message:

suse:/home/qtprograms/roughserial # ./roughserial -qws
Connected to VFB server: 640 x 480 x 32
Segmentation fault
suse:/home/qtprograms/roughserial #