to compare QByteArray and hexadecimal value

[Selim]

Hello everyone.
For a electronic application, i concieved an IHM which exchanges information with microcontroller.
I use the library QSerialport to send and receive information.

That is my reception function:

void MainWindow::readData()
{   
    QByteArray data = serial.readAll();
buffer.append(data);
      

    if(data.at(1)==0x87)
    {
        cout<<"Détection du ping " <<endl;
      //  ui->lineEdit_PingAnswer->setText(data.toStdString());
        ui->lineEdit_Device->setText("Device STHC1 Detected");
    }

}

When i send the byte 0x0087, data is : "\000\207"
data[0] : 0 '\0'
data[1] : (hex) 87 / (hex) 87

I want to compare if data(1) ==0x87 but it never enters in the if loop.

Thanks to spend time on my question.

Regards,

[jsulm]

@Selim if(data.at(1)==(char)0x87) works for me

[SGaist]

Hi,

QByteArray::at returns a char. You should rather test:

if (data.at(1) == '\x87')

[jsulm]

@SGaist warning: comparison is always false due to limited range of data type [-Wtype-limits]

[Selim]

Thanks for the quick answer.
The cast (char) works :).

I want also to create a string with 2 chars (data(0) and data(1) to fill the lineEdit_PingAnswer:
'''
ui->lineEdit_PingAnswer->setText(data........toStdString());
'''

But it's impossible to use .toStdString with data.at(1).

I have to build the string manually ?

[jsulm]

@SGaist Sorry my mistake, your version works as well

[jsulm]

@Selim How do you want to interpret the bytes? Do you want to show '0' for the first byte in the string and "87" or "0x87" for the second?

[Selim]

I want to display the two bytes (it's the PING_ID) like:
in hexadecimal : 0x0087
Or better :
0000'0000'1000'0111'

[jsulm]

@Selim For hex you can do it like this:

QString str("0x0");
str.append(QString::number(array.at(0)));
str.append(QString::number((uchar)array.at(1), 16));

[Selim]

Thanks, it's work wery well.
I will try to find function which translate u16 into binary form.

Thanks a lot for your help !

[jsulm]

@Selim Just do:

str.append(QString::number(array.at(0), 2));
str.append(QString::number((uchar)array.at(1), 2));

The only issue is: the first 0 byte isn't filled with 0

[Selim]

Thanks again ^^
Yes, i try and display the first 0 eight times