QSerialPort, randomly missing bytes

[SGaist]

Hi,

That's fairly intriguing...
Did you also compare the motherboards ?
What USB chip they have ?
Might be silly but could one of these machines be sent to you ?

[hskoglund]

To add to @SGaist, you could try setting up a real PC (not a VM) to eastern europe locale and time, since you're dealing with (perhaps) some hardware dependency. Running your app inside a VM that hardware gets emulated, i.e. not showing the exact same characteristics.

[Axel Spoerl]

Checking some basics:

• readyRead() fires as soon as something can be read, not everything.
• does QSerialPort live in one thread? Accessing it from multiple threads can be problematic and lead to unpredictable behaviour, actually pretty much the symptoms described.

@monegator said in QSerialPort, randomly missing bytes:

almost completely asynchronous

The almost raises an eyebrow. While having no personal experience with that specific class in a such a setting, I'd recommend to avoid mixing async and sync API.

Any chance you can show us some code?

[Kent-Dorfman]

and on the tablet that Moses dropped while coming down from the mountain, it said "Thou shalt use flow control"

[SGaist]

@Kent-Dorfman said in QSerialPort, randomly missing bytes:

and on the tablet that Moses dropped while coming down from the mountain, it said "Thou shalt use flow control"

Highly efficient on the Red Sea !

[Joe von Habsburg]

If you parse data with like "\r\n" may be you read begin incorrect index

void onReadyRead()
{
    static QByteArray buffer;

    buffer.append(_serial->readAll());

    int index;
    while((index = buffer.indexOf("\r\n")) != -1) {
        QByteArray line = buffer.left(index);
        buffer.remove(0, index + 2);

        if(!line.isEmpty()) {
            parseData(line);
        }
    }
}

If you use

_serial->read(N);
//or
_serial->readLine();

problem is here my opinion.

[FRAUBRJ]

On my Mac the solution I found is (message is in the global "inputQString")

void MainWindow::slotRead(void)
{
qint64 bw = 0;
QByteArray data;

data = port->readAll();
while (port->waitForReadyRead(15))
    data += port->readAll();

inputQString = data;

bw = inputQString.size();

//qDebug() << "inputString: " << inputQString << "  bw: " << bw;;
ReadRequest(bw);

} // slotRead

Perhaps adjust the ms parameter of "waitForReadyRead(ms)"

[Christian Ehrlicher]

@FRAUBRJ said in QSerialPort, randomly missing bytes:

Perhaps adjust the ms parameter of "waitForReadyRead(ms)"

Even better: don't use it at all.

[J.Hilk]

@FRAUBRJ I'm afraid, you haven't found a solution.

You have found a way that happens to work for your hardware and your data at the current time of the moon phase.

There is so much to improve here, but the important part is, you need some why to verify that you have all data you expect. Do not expect that all data is there when readAll() is called.

And despite what you expect, it is called exactly once, your while loop is literally doing nothing.

[jameswright]

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