Serial not writing directly

User94

I'm writing on serial but it ain't writing right away it is sending when it hits timeout (this is at the first time that I send data) then when I send data again it sends directly but the buffer is already not empty so what I get is the old values... Can anyone help?

This is the code:

if(serial->isWritable()){
            QString datasend = "123";
            serial->write(datasend.toStdString().c_str());
        }

        QString thisSerial = "";
        long long counter = 0;
        while(true){
            thisSerial = ReadInput();
            if(thisSerial != ""){
                  // do something
                  break;
            }
            else if(counter == 650000){
                QMessageBox msgBox;
                msgBox.setText("Couldn't read data");
                msgBox.setWindowTitle("Capture Error");
                msgBox.exec();
                return;
            }
            counter++;
     }

JonB

@User94
What "timeout"? And how do you know from your code whether it is the serial->write() which is not writing/sending immediately versus your ReadInput() (whose code you don't show us anyway) not receiving a reply right away?

I would suggest not using a while(true) ... ReadInput() ... break but doing it properly with signals & slots and allowing the Qt event loop to run, and see how it goes.

Kent-Dorfman

another example of trying to use traditional programming mechanisms in an event driven architecture. You should not use infinite loops in Qt code. It will amost certainly break the event handler loop that in intrinsic in Qt.

User94

@JonB it's because of the hardware that I know when serial data is sent (TX light blinks when data received)

JonB

@User94

@JonB said in Serial not writing directly:

I would suggest not using a while(true) ... ReadInput() ... break but doing it properly with signals & slots and allowing the Qt event loop to run, and see how it goes.