Parallel Interface

[r00tz]

Does anyone can help me how to interface Qt with parallel port? I'm developing a software that sends some commands to the parallel. Wich class may I use? Thanks

[zlatko]

Does anyone can help me how to interface Qt with parallel port? I'm developing a software that sends some commands to the parallel. Wich class may I use? Thanks

i'm not sure but i think that qt cant help you with it, you must use standart api approach

[high_flyer]

For which platform?
I implemented a basic Qt wrapped for parapin (the paraport driver for linux) if you want it I can post it.

[Cesar]

I guess you should create a subclass of QIODevice and implement all the platform-specific issues by yourself Something like this:

//ParalellPort.h
#include <QIODevice>
 
class ParalellPort : public QIODevice {
	Q_OBJECT
	public:
		ParalellPort(const QString &, QObject * = 0);
		virtual ~ParalellPort();
 
		virtual bool isSequential () const { return true; }
 
		virtual bool open(OpenMode);
		virtual void close ();
		//..
	protected:
		virtual qint64 readData ( char * data, qint64 maxSize );
		virtual qint64 writeData ( const char * data, qint64 maxSize );
	private:
		#ifdef Q_OS_UNIX
		QFile deviceFile;
		#endif
};
 
//ParalellPort.cpp
#include "ParalellPort.cpp"
 
ParalellPort::ParalellPort(const QString & port, QObject * parent) :
	QIODevice(parent)
	#ifdef Q_OS_UNIX
	, deviceFile(port)
	#endif
{
}
 
bool ParalellPort::open(OpenMode mode) {
	#ifdef Q_OS_UNIX
	return deviceFile.open(mode);
	#endif
 
	#ifdef Q_OS_MACX
	//...
	#endif
 
	#ifdef Q_OS_WIN32
	//...
	#endif
}
//...

//ParalellPort.h
#include <QIODevice>

class ParalellPort : public QIODevice {
	Q_OBJECT
	public:
		ParalellPort(const QString &, QObject * = 0);
		virtual ~ParalellPort();

		virtual bool isSequential () const { return true; }

		virtual bool open(OpenMode);
		virtual void close ();
		//..
	protected:
		virtual qint64 readData ( char * data, qint64 maxSize );
		virtual qint64 writeData ( const char * data, qint64 maxSize );
	private:
		#ifdef Q_OS_UNIX
		QFile deviceFile;
		#endif
};

//ParalellPort.cpp
#include "ParalellPort.cpp"

ParalellPort::ParalellPort(const QString & port, QObject * parent) :
	QIODevice(parent)
	#ifdef Q_OS_UNIX
	, deviceFile(port)
	#endif
{
}

bool ParalellPort::open(OpenMode mode) {
	#ifdef Q_OS_UNIX
	return deviceFile.open(mode);
	#endif
	
	#ifdef Q_OS_MACX
	//...
	#endif
	
	#ifdef Q_OS_WIN32
	//...
	#endif
}
//...

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A quote from TT's docs:

Subclasses of QIODevice are only required to implement the protected readData() and writeData() functions.

[high_flyer]

I guess you should create a subclass of QIODevice

Well, yes and no.
The 'problem' with the parallel port is that you can (and usually want to) manipulate individual pins. not just (or nesseseraly) transmit data.

[Cesar]

Well, yes and no.
The 'problem' with the parallel port is that you can (and usually want to) manipulate individual pins. not just (or nesseseraly) transmit data.

void ParalellPort::setPin(int pin, int value)
{
    int oldValue = getChar(pin);
    if (value != 0) {
        putChar(oldValue | 1 << pin);
    } else {
        putChar(oldValue & (~ (1 << pin)) );
    }
}
 
int ParalellPort::getPin(int pin)
{
    return (getChar() & (1 << pin)) ? 1 ? 0;
}

void ParalellPort::setPin(int pin, int value)
{
    int oldValue = getChar(pin);
    if (value != 0) {
        putChar(oldValue | 1 << pin);
    } else {
        putChar(oldValue & (~ (1 << pin)) );
    }
}

int ParalellPort::getPin(int pin)
{
    return (getChar() & (1 << pin)) ? 1 ? 0;
}

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[high_flyer]

Ok, here is my implementation, at the moment the fact its Qt has no advantage.
One could build in a polling mechanism that will send signals on pin state changes.
This clas works, it is being used in a program that controlls harware through the paraport.
You should install parapin and read the docs there.

[r00tz]

Well... I'd just like to thank both of you. This helped very very much, I got some tutorial about parallel port interfacing. With all code and tips you passed to me, I will implement it. Thanks a lot.

[wallyqt]

I tried the parapin drivers and it works good as root.
When using the parapin-kernel-driver i can access the port from user-space.
Do anybody know how to implement the kerneldriver with qt.
I am looking for something very similar "QParaport.zip" from "high_flyer".

I able to open the parapindriver with:
(set pins is also possible:
int kparappWidget::pushButtonOpen_clicked()
{
pardevice = open("/dev/ppdrv_device", 0);
if (pardevice < 0) {
fprintf(stderr, "pardevice open failed\n");
exit(-1);
}
return 0;
}

but when i call the close function, all widgets on the application mainWin
disappear and i only can close (kill) the app.

int kparappWidget::pushButtonClose_clicked()
{
close(pardevice);
return 0;
}

here is the code for setting pins:

void kparappWidget::pushButtonSetPins_clicked()
{
ioctl(pardevice, PPDRV_IOC_PINMODE_OUT, LP_PIN02);

ioctl(pardevice, PPDRV_IOC_PINSET, LP_PIN02 | LP_PIN03 | LP_PIN04 | LP_PIN05 | LP_PIN06 | LP_PIN07 | LP_PIN08 | LP_PIN09);
}

cheers wally

[high_flyer]

I tried the parapin drivers and it works good as root.
When using the parapin-kernel-driver i can access the port from user-space.

I am not sure you mean what your text says. i.e:
Do you mean you want to use the kernel module from user space, or, do you want to use the user space module with a user that is not root?

It could be that you have problem with read write right for non root users, you can fix that with chmod.

You can't use the kernel module from user space (and you shouldn't)
And if you don't need PIN10, (and from your code it seams that way) you don't need to - the user space module should be used - and you can the QParaport class for what you described here.

[wallyqt]

high_flyer,

you are right, its confusing because i didn't understand it myself not entirely.
I want to use the kernel-driver of parapin which i load during boot.
After the driver is once loaded i do not want to use root anymore.

In command-line apps it works perfect, but i have problems to close the
device properly in a kde-qt-app.

i think i should use Qiodevice.h and not mixing old and new stuff together,
but i am not a good programmer. So i ask in this forum.

As far as i understand you code sample - it needs root previleges.
But i want to use the parapin stuff also in a larger application which not should run as root.

Maybe i do some fundamnetal error

cheers wally

[high_flyer]

I want to use the kernel-driver of parapin which i load during boot.

No, you want to use the user space module
Only the system is allowed to access the kernel space module.
Read the parapin documentation.

The problem with QParaport is that it is written for Qt3.
And I haven't had a look at this code for a very long time, so I don't know how easy it should be to port it to Qt4. (I forgot about this during the last post)
But I think it should be just a matter of changing the header deceleration.

As far as i understand you code sample - it needs root privileges.

The *code* doesn't require root privileges.
Under linux, you can set access privileges using the chmod command.
read the chmod command man pages for usage. (its simple)

i think i should use Qiodevice.h and not mixing old and new stuff together,

QIOdevice could be good if you'd want to implement the driver your self.
But if you use the ready made parapin driver, all you can do is either wrap it (as I did with QParaport) or use it directly.
It has nothing to do with mixing new and old.