Basic Communications with QSerialPort - c++

Question

I am trying to rig up some basic serial communications in QT
I am getting the port COM19 from QSerialPortInfo, and I speaking successfully to the port via Arduino. However, I cannot get anything back via QT.
#include "mainwindow.h"
#include <QApplication>
#include <QDebug>
#include <QTextStream>
#include <QFile>
#include <QtSerialPort/QSerialPort>
#include <QtSerialPort/QSerialPortInfo>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
foreach(const QSerialPortInfo &info, QSerialPortInfo::availablePorts()){
qDebug() << "Name :" << info.portName();
qDebug() << "Description :" << info.description();
qDebug() << "Manufactuer :" << info.manufacturer();
QSerialPort serial;
serial.setPort(info);
if(serial.open(QIODevice::ReadWrite))
qDebug() << serial.errorString();
serial.write("M114 \n");
qDebug() << serial.readAll();
serial.close();
// Now we need to send and receive commands
serial.setPortName("COM19");
serial.setBaudRate(QSerialPort::Baud57600);
serial.setDataBits(QSerialPort::Data8);
serial.setParity(QSerialPort::NoParity);
serial.setStopBits(QSerialPort::OneStop);
serial.setFlowControl(QSerialPort::NoFlowControl);
if(serial.open(QIODevice::ReadWrite)){
qDebug() << "opened";
}else{
qDebug() << "Not opened";
}
qDebug() << serial.errorString();
serial.write("M114 \n");
qDebug() << serial.readAll();
serial.close();
}
MainWindow w;
w.show();
return a.exec();
}
As you can see, I am trying a simple connection along the lines of the documentation, and one where I write out all the baud rate information. They throw two different errors.
Like I said, I am connecting via arduino to this same port and having success. Any ideas what's wrong?
Name : "COM19"
Description : "USB Serial (Communication Class, Abstract Control Model)"
Manufactuer : "PJRC.COM, LLC."
"Unknown error"
""
opened
"The handle is invalid."
""
Any ideas for what I am doing wrong?
My idea is to send commands to the device, and read them back to the console.

Answer 1

the code looks a bit confuse. You open all port available and then you try to do something wrong.
NOTE: You use a GUI application like a shell application. It is wrong.
Try:
#include "mainwindow.h"
#include <QApplication>
#include <QDebug>
#include <QTextStream>
#include <QFile>
#include <QtSerialPort/QSerialPort>
#include <QtSerialPort/QSerialPortInfo>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QSerialPort serial;
serial.setPortName("COM19");
if(serial.open(QIODevice::ReadWrite)){
//Now the serial port is open try to set configuration
if(!serial.setBaudRate(QSerialPort::Baud57600))
qDebug()<<serial.errorString();
if(!serial.setDataBits(QSerialPort::Data8))
qDebug()<<serial.errorString();
if(!serial.setParity(QSerialPort::NoParity))
qDebug()<<serial.errorString();
if(!serial.setStopBits(QSerialPort::OneStop))
qDebug()<<serial.errorString();
if(!serial.setFlowControl(QSerialPort::NoFlowControl))
qDebug()<<serial.errorString();
//If any error was returned the serial il corrctly configured
serial.write("M114 \n");
//the serial must remain opened
if(serial.waitForReadyRead(100)){
//Data was returned
qDebug()<<"Response: "<<serial.readAll();
}else{
//No data
qDebug()<<"Time out";
}
//I have finish alla operation
serial.close();
}else{
qDebug()<<"Serial COM19 not opened. Error: "<<serial.errorString();
}
MainWindow w;
w.show();
return a.exec();
}

Answer 2

Starting with the tenth port, his name will be \\.\COM10
You can reassign the port to a different number in Device Manager