QtSerialPort synchronous approach

[codein]

Hi!
i'm trying to communicate some device that have been programmed myself to PC. Just a simple one to test QtSerialPort. In terminal example on QtSerialPort's help its work fine.
Here is the reading result :

308
307
309
308
.
.
.

But when i write my code using synchronous approach, the reading is terrible. Here is the code :

#include <QtCore/QCoreApplication>
#include <QtDebug>
#include <QtAddOnSerialPort/serialport.h>
 
QT_USE_NAMESPACE_SERIALPORT
 
void setup();
SerialPort serial;
 
int main(int argc, char *argv[])
{
    serial.setPort("COM20");
    serial.open(QIODevice::ReadOnly | QIODevice::Unbuffered);
    setup();
 
    QCoreApplication a(argc, argv);
 
    //here is the problem
    while (serial.waitForReadyRead(100)) {
        qDebug() << serial.read(8);
    }
 
    return a.exec();
}
 
void setup()
{
    serial.setRate(SerialPort::Rate9600);
//    serial.setBaudRate(AbstractSerial::BaudRate9600);
    serial.setDataBits(SerialPort::Data8);
    serial.setParity(SerialPort::NoParity);
    serial.setStopBits(SerialPort::OneStop);
    serial.setFlowControl(SerialPort::NoFlowControl);
}

#include <QtCore/QCoreApplication>
#include <QtDebug>
#include <QtAddOnSerialPort/serialport.h>

QT_USE_NAMESPACE_SERIALPORT

void setup();
SerialPort serial;

int main(int argc, char *argv[])
{
    serial.setPort("COM20");
    serial.open(QIODevice::ReadOnly | QIODevice::Unbuffered);
    setup();

    QCoreApplication a(argc, argv);

    //here is the problem
    while (serial.waitForReadyRead(100)) {
        qDebug() << serial.read(8);
    }
    
    return a.exec();
}

void setup()
{
    serial.setRate(SerialPort::Rate9600);
//    serial.setBaudRate(AbstractSerial::BaudRate9600);
    serial.setDataBits(SerialPort::Data8);
    serial.setParity(SerialPort::NoParity);
    serial.setStopBits(SerialPort::OneStop);
    serial.setFlowControl(SerialPort::NoFlowControl);
}

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and the result :

"308"
"307"
"308"
"3"
"0"
"9"
"
"
"3"
"0"
"7"
"
"3"
"0"
"9"
.
.

Well previusly i using QSerialDevice for Serial Communication its work fine with simple reading like that. Until i use it for multithreading, it mostly crash all over time. Then i use QtSerialPort for multithreading its work fine until i found the reading is bad. Is there a way to solve that problem?