why i cant write to serial ? | Arduino Uno , QT 5.9.9 , C++ Question

[Lime1]

My code can read from arduino uno fine, but it cannot write to it. I thought about it because I was trying to write while reading data in the same time , so i commented the part that read data, but it still doesn't work. Here is the call for the code

uno.write_to_arduino("1"); //! testing

here is the arduino init (it work fine beside the writing part)

#include <QDebug>

#include "arduino.h"

Arduino::Arduino()
{
    data = "";
    arduino_port_name = "";
    arduino_is_available = false;
    serial = new QSerialPort;
}

QString Arduino::getarduino_port_name()
{
    return arduino_port_name;
}

QSerialPort *Arduino::getserial()
{
    return serial;
}

int Arduino::connect_arduino()
{ // recherche du port sur lequel la carte arduino identifée par  arduino_uno_vendor_id
    // est connectée
    foreach (const QSerialPortInfo &serial_port_info, QSerialPortInfo::availablePorts())
    {
        if (serial_port_info.hasVendorIdentifier() && serial_port_info.hasProductIdentifier())
        {
            if (serial_port_info.vendorIdentifier() == arduino_uno_vendor_id && serial_port_info.productIdentifier() == arduino_uno_producy_id)
            {
                arduino_is_available = true;
                arduino_port_name = serial_port_info.portName();
            }
        }
    }
    qDebug() << "arduino_port_name is :" << arduino_port_name;
    if (arduino_is_available)
    { // configuration de la communication ( débit...)
        serial->setPortName(arduino_port_name);
        if (serial->open(QSerialPort::ReadWrite))
        {
            serial->setBaudRate(QSerialPort::Baud9600); // débit : 9600 bits/s
            serial->setDataBits(QSerialPort::Data8);    // Longueur des données : 8 bits,
            serial->setParity(QSerialPort::NoParity);   // 1 bit de parité optionnel
            serial->setStopBits(QSerialPort::OneStop);  // Nombre de bits de stop : 1
            serial->setFlowControl(QSerialPort::NoFlowControl);
            return 0;
        }
        return 1;
    }
    return -1;
}

int Arduino::close_arduino()
{
    if (serial->isOpen())
    {
        serial->close();
        return 0;
    }
    return 1;
}

QByteArray Arduino::read_from_arduino()
{
    if (serial->isReadable())
    {
        data = serial->readAll(); // récupérer les données reçues

        return data;
    }
}

int Arduino::write_to_arduino(QByteArray d)
{
    if (serial->isWritable())
    {
        serial->write(d); // envoyer des donnés vers Arduino
        qDebug() << "Data sent to Arduino: " << d;
    }
    else
    {
        qDebug() << "Couldn't write to serial!";
    }
}

i get "Couldn't write to serial!" is there at least a way to debug the issue more ?

[Lime1]

Also, switching the USB port did not work.
and typing the command in the arduino IDE consol works fine

[Pl45m4]

@Lime1 said in why i cant write to serial ? | Arduino Uno , QT 5.9.9 , C++ Question:

Also, switching the USB port did not work.

What should this do? :)

Maybe you need some terminating \r\n (CR LF)
Try to send it at the end of your data.

What does QSerialPort::error() return?

[SGaist]

Hi,

In addition to @Pl45m4, you don't print any information if the opening of the serial port failed. Doing that will help track the issue.