Sending string by serial port

ToPo

Hi Pros,
i have a problem with sending a string by the serial port.
It´s just a little "hello-World" program...

The port opens correctly, i´m sending a constant string after opening:

serial->write("Hello World!\n");

In the UI i´ve created a slider and a label. For the slider i´ve created a slot:

connect(ui->slider_1, SIGNAL(valueChanged(int)), this, SLOT(slider_changed(int)));

And this is the subroutine called by the slot:

void MainWindow::slider_changed(int value)
{
QString buffer = QString("%1\n").arg(QString::number(value));
serial->write((char*)buffer.data(), buffer.length());
serial->QSerialPort::waitForBytesWritten(-1);
ui->test_label->setText(buffer);
}

So far, so good. The program compiles fine, the "Hello World" is send. I´ve connected two FTDI on different USB-Ports and control the output via a terminal.

As soon as i slide the slider the label is changed to the integer value of the slider (0-255).
BUT: On the serial port i just receive something like "4.14.0". The \n isn´t send at all.
I tried already to fill the buffer via sprintf, exactly the same problem.

What is the problem???
Hope you can help me,
thanks

Tobias

michelson

Mayby try:
serial->write( buffer.toStdString().c_str(), buffer.size() );

ToPo

@michelson said:

serial->write( buffer.toStdString().c_str(), buffer.size() );

Tanks a lot! Now it works fine :)

SGaist

Hi and welcome to devnet,

There's no need to use QString and all these conversions. You should use QByteArray directly. Something like:

QByteArray buffer = QByteArray::number(value) + "\n";
serial->write(buffer);