QT reading Serialport of Arduino

[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