[Linux] /dev/ttySAC0 - how can I read that file?

[Tomasz]

Hello!

I want to read (only read) /dev/ttySAC0. I wrote simple program in C, and It works fine in console. Now I want to do the same using QT. But when I want to read from that file program hangs. Any ideas what can I do? Data in that file is refreshing in every 1 second and it comes by RS232 from another device.

thanks in advance
best regards
Tomasz

[tbscope]

What have you tried so far?
You mention that your program hangs.

[Tomasz]

I've tried something like this:

QFile file("/dev/ttySAC2");
 
    int len = 0;
    char buffer[100];
 
 
                    if (!file.open(QIODevice::ReadOnly)) {
                      printf("error!");
                    } else {
                        int pending = file.bytesAvailable();
                        out << QString::number(pending) << endl;
 
                        if ( pending > 0 ) {
                            len = file.read(buffer, sizeof buffer - 1);
                        }
 
                        if (len > 0) {
                             [...]
                        }

QFile file("/dev/ttySAC2");

    int len = 0;
    char buffer[100];


                    if (!file.open(QIODevice::ReadOnly)) {
                      printf("error!");
                    } else {
                        int pending = file.bytesAvailable();
                        out << QString::number(pending) << endl;

                        if ( pending > 0 ) {
                            len = file.read(buffer, sizeof buffer - 1);
                        }

                        if (len > 0) {
                             [...]
                        }

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And also something with QTextStream. Program hangs when it is trying to read from that file. In console program there was no problem.

thanks in advance
best regards
Tomasz

[kuzulis]

Tomasz,

try use library for serial programming in Qt4:
1. QSerialDevice (in gitorgious.org)
2. qextserialport (in google.com)
3. qserialport (in gitorgious.org)

and etc. analogs.

Choose yourself what you like.

[Tomasz]

But maybe someone have any idea how can i read from that file using standard classes?

thanks in advance
best regards
Tomasz

[wysota]

Use QLocalSocket and optionally QSocketNotifier.

[Tomasz]

Use QLocalSocket and optionally QSocketNotifier.

How can I use QLocalSocket with file?

thanks in advance
best regards
Tomasz

[squidge]

How about:

int fd = open("/dev/ttySAC0", O_RDONLY|O_NONBLOCK);
QSocketNotifier *socNotify = new QSocketNotifier(fd, QSocketNotifier::Read, this);
connect(socNotify, SIGNAL(activated(int)), this, SLOT(your_read_function(int)));

int fd = open("/dev/ttySAC0", O_RDONLY|O_NONBLOCK);
QSocketNotifier *socNotify = new QSocketNotifier(fd, QSocketNotifier::Read, this);
connect(socNotify, SIGNAL(activated(int)), this, SLOT(your_read_function(int)));

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[wysota]

How can I use QLocalSocket with file?

/dev/ttySAC0 is not a file, it's a stream you can connect to using QLocalSocket. Or you can use QSocketNotifier with native stream handling (see the example squidge gave you).