QSerialPort Open() return error: No such file or directory

Myg0t

Hi there, Currently I'm using a Raspberry Pi 2 & 3 with the latest version of Rasbian (Jessie). I'm struggling to get the serial port working in QT. I'm using Xbee radio transmitter/receivers. I know for a fact that they do work because I can communicate between them using cutecom. But everytime I run my code (which is largely based on of the tutorials) I receive an error in the console saying "Error: No such file or directory" and this pops up when I run serial->open(QSerialPort:ReadWrite). here is my code:

XbeeCom.cpp:

#include "xbeecom.h"

#include <QSerialPortInfo>
#include <QSerialPort>

#include <QDebug>
#include <QList>

XbeeCom::XbeeCom(QObject *parent) :
    QObject(parent)
{
        serial = new QSerialPort(this);

        QList<QSerialPortInfo> ports = QSerialPortInfo::availablePorts();

        for(int i = 0; i < ports.size(); i++){
            qDebug() << ports[i].portName();
        }

        QSerialPortInfo info("ttyUSB0");
        qDebug() << "Name :" << info.portName();
        qDebug() << "Description : " << info.description();
        qDebug() << "Manufacturer :" << info.manufacturer();

        // Example use QSerialPort
        serial->setPortName(info.portName());
//        serial->setBaudRate(9600);
//        serial->setDataBits(QSerialPort::Data8);
//        serial->setStopBits(QSerialPort::OneStop);
//        serial->setParity(QSerialPort::NoParity);
//        serial->setFlowControl(QSerialPort::NoFlowControl);

        connect(serial,
                &QSerialPort::bytesWritten,
                this,
                &XbeeCom::handleBytesWritten
                );

        connect(serial,
                static_cast<void (QSerialPort::*)(QSerialPort::SerialPortError)>(&QSerialPort::error),
                this,
                &XbeeCom::handleError
                );

        connect(serial,
                &QSerialPort::readyRead,
                this,
                &XbeeCom::readData
                );

        if (serial->open(QSerialPort::ReadWrite)){
            serial->setBaudRate(9600);
            serial->setDataBits(QSerialPort::Data8);
            serial->setStopBits(QSerialPort::OneStop);
            serial->setParity(QSerialPort::NoParity);
            serial->setFlowControl(QSerialPort::NoFlowControl);
            qDebug() << "Hello world";
            QByteArray data(QString("Hello world").toStdString().c_str());
            bytesWritten = serial->write(data);

            if(bytesWritten == -1){
                qDebug() << QString("Failed to write data to port %1, error: %2").arg(serial->portName()).arg(serial->errorString());

            }
            else if(bytesWritten != serial->size()){
                qDebug() << "Failed to write all data";
            }

            serial->close();
        }
        qDebug() << "After if statement";
}

void XbeeCom::readData(){
    QByteArray data = serial->readAll();
    qDebug() << QString(data);
}

void XbeeCom::handleBytesWritten(qint64 bytes){
    bytesWritten += bytes;
    if(bytesWritten == serial->size()){
        bytesWritten = 0;
        qDebug() << ("Data successfully sent to port");
    }
}

void XbeeCom::handleError(QSerialPort::SerialPortError serialPortError){
    if(serialPortError == QSerialPort::WriteError){
        qDebug() << QString("An I/O error occurred while writing the data to port %1, error: %2")
                    .arg(serial->portName())
                    .arg(serial->errorString());
    }
    else
        qDebug() << QString("Some other error on port %1, error: %2")
                    .arg(serial->portName())
                    .arg(serial->errorString());
}

And here is my XbeeCom.h:

#ifndef XBEECOM_H
#define XBEECOM_H

#include <QObject>
#include <QSerialPort>


class XbeeCom : public QObject
{
    Q_OBJECT

public:
    explicit XbeeCom(QObject *parent = 0);

private:
    QSerialPort *serial;
    qint64 bytesWritten;
    QByteArray writeData;


signals:

private slots:
    void handleBytesWritten(qint64 bytes);
    void handleError(QSerialPort::SerialPortError serialPortError);
    //void handleTimeout();
    void readData();

public slots:


};

#endif // XBEECOM_H

I'm not trying to do anything super special here.. Just send some sample data and hope that I receive it on the other end...

Let me know if you guys need more information.

Thank you!!!

SGaist

Hi and welcome to devnet,

Might be a silly question but are you sure that your QSerialPortInfo is valid ?

I'd compare it with what availableReports returns.

Myg0t

As far as I am aware, yes it should be a valid port. I know that the XBee is connected on ttyUSB0. And when this portion of code is ran:

QSerialPortInfo info("ttyUSB0");
        qDebug() << "Name :" << info.portName();
        qDebug() << "Description : " << info.description();
        qDebug() << "Manufacturer :" << info.manufacturer();

My output is:
Name: "ttyUSB0"
Description : "FT231 USB UART"
Manufacturer: "FTDI"

I assume this means its a valid port?

Thanks!

SGaist

Do you have the rights to access that port ?

Myg0t

Yes, I believe that I do. I'm logged in as the pi user, and I'm able to run cutecom (without sudo) and send and receive messages on the port. So I assume that the pi user has permissions to do so. The weird thing is that the serial examples work fine. So I assume that I must be missing something that they are doing. But I'm not seeing it...

SGaist

Then I'd recommend taking a look the example code and rewrite yours to match it.