[PLEASE HELP] how to make a barcode receiver?

[A Former User]

@JKSH ok i could find the right port and passed from

if( port->open(QSerialPort::ReadOnly) )

now I'm stuck on

if( !port->bytesAvailable() )
                  return;

it always return
witch mean no bytes is available

[JKSH]

@davidlabib said in [PLEASE HELP] how to make a barcode receiver?:

now I'm stuck on

if( !port->bytesAvailable() )
                  return;

it always return
witch mean no bytes is available

Did you choose the correct settings? How is your scanner configured for the following?

• Baud rate
• Parity
• Data bits
• Stop bits
• Flow control

[A Former User]

@JKSH
Baud rate 115200

[aha_1980]

@davidlabib

I guess you don't have permission to use the serial port.

Please type: ls -l /dev/<your-serial-port-name> in a terminal and post the output here.

[A Former User]

@aha_1980 yes i don't have
but i use sudo

[SGaist]

Don't develop as super-user.

The command @aha_1980 will show the user and group affected to the device. Add your own user to that group, then log out and log in again and you will have access to the device.

[aha_1980]

@davidlabib Better add your user to the group dialout and reboot your computer.

Of course sudo works, but may give new problems.

As @JKSH wrote, not only baudrate is important.

I'd suggest to use a terminal program first to verify your scanner works correctly. Then use the same parameters for your code.

[A Former User]

solved PermissionError
now iam stuck in this

   QSerialPort* port = new QSerialPort( this );
   QSerialPortInfo::availablePorts();
   port->setBaudRate( QSerialPort::Baud115200 ); // possible something else, also check the manual
   port->setPort( QSerialPortInfo("ttyACM0") ); // COM port - check Device Manager for connected port
   QSerialPortInfo::availablePorts();
   if( port->open(QSerialPort::ReadOnly) )
   {
       ui->label->setText("port opended sucssefully");
           connect(port, &QSerialPort::readyRead, this, [port]() {
                 if( !port->bytesAvailable() )
                     qDebug() << port->error(); ////////// I'm stuck here it seems that there is no data
                      return;
                 const QByteArray scannedData = port->readAll();
                 // ...
           });
   }
   else
   {
       ui->label->setText("Error");
       qDebug() << port->error();
       QSerialPortInfo::availablePorts();
   }
}

also it will execute this if i clicked a button what if the user didn't click

[jsulm]

@davidlabib said in [PLEASE HELP] how to make a barcode receiver?:

qDebug() << port->error(); ////////// I'm stuck here it seems that there is no data

Do you mean the slot is called but bytesAvailable() returns 0? If so what does

qDebug() << port->error();

print out?

"also it will execute this if i clicked a button what if the user didn't click" - yes, if user does not click the button it will not be executed.

[A Former User]

@jsulm said in [PLEASE HELP] how to make a barcode receiver?:

Do you mean the slot is called but bytesAvailable() returns 0? If so what does

qDebug() << port->error();

print out?

nothing

[jsulm]

@davidlabib Looks like the slot isn't called.
This code is broken:

if( !port->bytesAvailable() )
    qDebug() << port->error(); ////////// I'm stuck here it seems that there is no data
    return;
const QByteArray scannedData = port->readAll();

It shoud be

if( !port->bytesAvailable() ) {
    qDebug() << port->error(); ////////// I'm stuck here it seems that there is no data
    return;
}
const QByteArray scannedData = port->readAll();

[A Former User]

@jsulm i have fixed it and still nothing

[A Former User]

finally solved
@Pablo-J-Rogina you were right it's lower level problem
put this in the constructor
and every barcode scan it will

qDebug() << scannedData;

Of course need modifying
but here is the code

    QSerialPort* port = new QSerialPort( this );
    QSerialPortInfo::availablePorts();
    port->setBaudRate( QSerialPort::Baud115200 ); // possible something else, also check the manual
    port->setPort( QSerialPortInfo("COMX") ); // COM port - check Device Manager for connected port
    if( port->open(QSerialPort::ReadOnly) )
    {
        ui->label->setText("hi");
            connect(port, &QSerialPort::readyRead, this, [port]() {
                  const QByteArray scannedData = port->readAll();
                  qDebug() << scannedData;
                  // ...
            });
    }