doesn't print the ( µ ) symbol correctly in qt

[Ramkumar Mohan]

Hi,
I am usning Thermal printer doesn't print the ( µ ) symbol correctly ,

My code :-

 void MainWindow::on_pushButton_clicked()
 {
       QString teststr3 = QString().fromLatin1("\xb5");
       Printer *p = new Printer();
       std::cout << "Trying to open port" << std::endl;
       bool res = p->open("/dev/ttyS0");
       std::cout << "Status: " << res << std::endl;
       if (!res)
       {
             std::cerr << "Error opening port, aborting" << std::endl;
             return (0);
        }
        p->feed();
        p->setAlign(Printer::LEFT);
        p->write("  symbol    : "   + teststr3);
        p->feed();
        p->close();
        return 1;
  }

Output:-

how to fit it....

[hskoglund]

Hi, your printer does not seem to like UTF8/Unicode and instead outputs it as 2 characters in the Code Page 437.
So either switch your printer to Unicode/UTF8 mode or change your teststr3 to the character \xE6 ( µ in Code Page 437).
Perhaps easiest is try something like:

char c = '\xE6';
p->write(c);

[Ramkumar Mohan]

@hskoglund said in doesn't print the ( µ ) symbol correctly in qt:

char c = '\xE6';
p->write(c);

I tried this way but it keeps getting junk.

  int MainWindow::on_Logo_Btn_3_clicked()
  {

     char data = '\xb5';
     qDebug()<<"Data : "<<data;
     Printer *p = new Printer();
     std::cout << "Trying to open port" << std::endl;
     bool res = p->open("/dev/ttyS0");
     std::cout << "Status: " << res << std::endl;
     if (!res) 
     { 
           std::cerr << "Error opening port, aborting" << std::endl;
           return (0);
     }
     p->reset();
     p->setAlign(Printer::MIDDLE);
     p->setBold(true);
     p->writes(&data);
     p->setBold(false);
     p->feed();
     p->feed();
     p->setAlign(Printer::LEFT);
     p->close();
     return 1;
 }

[piervalli]

@Ramkumar-Mohan
If I see corretly, the printer is a retail printer, usually they have a single code page. You should check before the printer.

[hskoglund]

Hi, because you're using p->writes(&data); I think you need a terminating '\x00' zero byte also. (Since there's none that's why you get all those junk characters).
So try

char data[2] = { '\xE6', '\x00' };
... // and then later
p->writes(data);

Edit: I think if you want to print a µ and not a ╡ you should use '\xE6', not '\xb5' more here https://en.wikipedia.org/wiki/Code_page_437

[ChrisW67]

@Ramkumar-Mohan said in doesn't print the ( µ ) symbol correctly in qt:

To expand on @hskoglund's input.

QString teststr3 = QString().fromLatin1("\xb5");
This puts a 16-bit number containing 0x00b5 into the QString. This is UTF-16 form of the character you provided from the ISO-8859-1 (Latin1) set.

p->write(" symbol : " + teststr3);
This code will probably invoke this operator to produce a QString containing both parts.

You do not say what the write() function is expecting so I am guessing it is a crude char*. The QString will be cast to char* using UTF-8 encoding by default. This generates two bytes for the last character in the QString:

• 0xC2 -> Which is the ┬ character in the 8-bit Code Page 437
• 0xB5 -> Which is the ╡character in the Code Page 437

Those are the characters you see on the paper.
To get a µ in the code page (on that printer) you need to send a 0xe6 byte.

You can deliberately convert your QString to a 8-bit string in the correct encoding using QTextCodec (assuming full ICU support).

QString string = "...";
QTextCodec *codec = QTextCodec::codecForName("CP437");
QByteArray encodedString = codec->fromUnicode(string);
p->write(encodedString.constData());

Of course, not everything you can put in a QString has a Code Page 437 equivalent.

[Ramkumar Mohan]

@ChrisW67

Now , working fine ,

 int num =230;
 char data = char(num);
 p->write(data);

Thank you....