if(serial->bytesAvailable()>=160)

I change it to

while(serial->bytesAvailable()>=160)

So if buffer has more values it should read them too. Once is less then 160 bytes, it will leave the slot. It iwll come back when "readyRead" signal is emitted again.

void QIODevice::readyRead():
" you should always emit readyRead() when new data has arrived (do not emit it only because there's data still to be read in your buffers"

Everything was working with Qt5.7.1. Maybe i have to make a new loop to check if buffer still has values more ore equal than 160. If so, it should be read them, because the signal "readyRead()" wont be send out again.

connect(serial, &QSerialPort::readyRead, this, &QelcSystemSerialport::run);

Everytime QSerialPort send "readyRead" it goes to slot "run"

A MCU is sending values to Qt Application. I debug MCu and it is sending, i measured the RX and TX with an oscilloscope and the values are send out.
So the issue is in Qt

QByteArray Array=serial->readAll();
it really does receive all bytes but the issue is when i want to read a specific amount of bytes like 160 and not all:

So everytime i do this:
serial->read(buffer,160);

The QSerialPort buffer "erase" all bytes that where read from "read()" function plus the left ones inside.

Why is the internal QSerialPort buffer been completely erased if i do "read(buffer,160);"
I understand if i do "readAll()" it will read all values from serialport and delete them.
But why is "read()" function doing the same in Qt5.9.1?

What i am doing is waiting so that bytes available are equal or greater than 160

Which leads me to the question, how you are doing that.

Also, on which platform are you experiencing this behavior?