QT reading Serialport of Arduino

[mimamrafi]

Hi. all. i'm stuck in reading some string from arduino. The Serial Port didn't open automatically when I debug first time in QT. But when I open the serial monitor from Arduino IDE, then I close it, then I debug again in QT, then the arduino begin to send its string. But when I upload the code to arduino again, then I debug the QT, it didn't sent anything. It seems my arduino didn't open automatically of its serial port. How can I debug the QT without open the serial monitor from arduino ide in the first?

This is my simple code

//================ Arduino Code ==============
void setup()
{
    Serial.begin(9600);
    pinMode (led, OUTPUT);
}  

void loop()
{
    Serial.println ("test");
}

and this is QT Code

SerialPortManager::SerialPortManager(QObject *parent) :
    QObject(parent)
{
   arduino = new QSerialPort(this);
   connect(arduino, SIGNAL(readyRead()), this, SLOT(readData()));
}

void SerialPortManager::openSerialPort()
{
   arduino->setPortName("COM8");
   arduino->open(QIODevice::ReadWrite);
   arduino->setBaudRate(QSerialPort::Baud9600);
   arduino->setDataBits(QSerialPort::Data8);
   arduino->setParity(QSerialPort::NoParity);
   arduino->setStopBits(QSerialPort::OneStop);
   arduino->setFlowControl(QSerialPort::NoFlowControl);
}

void SerialPortManager::readData()
{
    QByteArray data = arduino->readAll();
//    console->putData(data);
    qDebug() << "UART:" << data;
}

[mimamrafi]

Hai everyone. I found some clues about this topic. The serial communication have to enable the DTR (Data Terminal Ready). So this is my current code that I used

void SerialPortManager::openSerialPort()
{
   arduino->setPortName("COM8");
   arduino->open(QIODevice::ReadWrite);
   arduino->setBaudRate(QSerialPort::Baud9600);
   arduino->setDataBits(QSerialPort::Data8);
   arduino->setParity(QSerialPort::NoParity);
   arduino->setStopBits(QSerialPort::OneStop);
   arduino->setFlowControl(QSerialPort::NoFlowControl);
   arduino->setDataTerminalReady(true);
}

Actually, I don't know why its working, but some of tutorial it's not a problem without writing setDataTerminalReady

[jsulm]

@mimamrafi said in QT reading Serialport of Arduino:

The Serial Port didn't open automatically

What do you mean? Do you mean arduino->open(QIODevice::ReadWrite); returns false (you should check the return value!)?

[J.Hilk]

@mimamrafi said in QT reading Serialport of Arduino:

void SerialPortManager::openSerialPort()
{
arduino->setPortName("COM8");
arduino->open(QIODevice::ReadWrite);
arduino->setBaudRate(QSerialPort::Baud9600);
arduino->setDataBits(QSerialPort::Data8);
arduino->setParity(QSerialPort::NoParity);
arduino->setStopBits(QSerialPort::OneStop);
arduino->setFlowControl(QSerialPort::NoFlowControl);
}

you have to open the serial port after setting the parameters.

[mimamrafi]

@jsulm yes, it return false. but after I open the serial monitor in Arduino IDE, then I close the serial monitor in arduino ide, then I debug the qt. now it return true. How can I debug the QT without open the serial monitor in arduino ide in the first time?

[jsulm]

@mimamrafi Please read what @J-Hilk wrote

[mimamrafi]

@J-Hilk it is the command to open the serial port right?

arduino->open(QIODevice::ReadWrite);

[jsulm]

@mimamrafi said in QT reading Serialport of Arduino:

it is the command to open the serial port right?

Yes, it should be AFTER you set the parameters (like setFlowControl).

[mimamrafi]

@jsulm yes, I have been open it and the output is true, but my issue is the arduino send nothing to serial when I debug the QT first. If I open the serial monitor and close it again then debug the QT, it works properly

[jsulm]

@mimamrafi I don't know how your Arduino side is working, so can't comment

[J.Hilk]

@mimamrafi said in QT reading Serialport of Arduino:

yes, I have been open it and the output is true

yes, thats obvious, but did you open it after setting the settings ? e.g:

void SerialPortManager::openSerialPort()
{
arduino->setPortName("COM8");
arduino->setBaudRate(QSerialPort::Baud9600);
arduino->setDataBits(QSerialPort::Data8);
arduino->setParity(QSerialPort::NoParity);
arduino->setStopBits(QSerialPort::OneStop);
arduino->setFlowControl(QSerialPort::NoFlowControl);

arduino->open(QIODevice::ReadWrite);
}

assuming of course, those are the same settings as the other program uses.

[mimamrafi]

@jsulm I only send

Serial.println ("test"); 

in void loop

[mimamrafi]

@J-Hilk Hey, I've got a clue. I'm using Arduino leonardo, I don't know why it didn't send the serial to QT without open the serial monitor. When I try Arduino UNO, it works properly without open the serial monitor first

[J.Hilk]

@mimamrafi try adding a sleep/delay at the end of your Arduino loop, see if that improves things.

[kuzulis]

@jsulm said in QT reading Serialport of Arduino:

Yes, it should be AFTER you set the parameters (like setFlowControl).

No. It is irrelevant.

[J.Hilk]

@kuzulis I was about to vehemently deny this, but then I noticed the setters have boolean return type.

I was only going on the notes from https://doc.qt.io/qt-5/qserialport.html#open
that says it sets the settings during open().

did this change in one of the newer versions? apparently not. At least not as far back as 5.12

[mimamrafi]

@J-Hilk No, it still print nothing. Maybe, I will switch to arduino uno. It's hardware issue, not the QT. Thanks for help

[mimamrafi]

Hai everyone. I found some clues about this topic. The serial communication have to enable the DTR (Data Terminal Ready). So this is my current code that I used

void SerialPortManager::openSerialPort()
{
   arduino->setPortName("COM8");
   arduino->open(QIODevice::ReadWrite);
   arduino->setBaudRate(QSerialPort::Baud9600);
   arduino->setDataBits(QSerialPort::Data8);
   arduino->setParity(QSerialPort::NoParity);
   arduino->setStopBits(QSerialPort::OneStop);
   arduino->setFlowControl(QSerialPort::NoFlowControl);
   arduino->setDataTerminalReady(true);
}

Actually, I don't know why its working, but some of tutorial it's not a problem without writing setDataTerminalReady