How to open more than once SerialPort

mrjj

@erytcg said in How to open more than once SerialPort:

Almost but one fatal error !

void MainWindow::addAvailableSerialPorts()
{
QVector<QSerialPort *> v; <<<< This is a local var. It should be in class. windows .h. should not be defined here. only used.

So in
void MainWindow::openSerialPort(int index)
{
QSerialPort * serialPort = v[index]; <<< what v is this . it cannot be the one from addAvailableSerialPorts as that was local.

erytcg

ok I add *QVector<QSerialPort > v; to private: mainwindow.h
I have problem with close function port chooseing from list widget

mrjj

@erytcg

you need to use the row int as index

foreach(QListWidgetItem * item, items) {
int index= ui->listWidget->row(item); //
closeSerialPort( index);

erytcg

Hey it's good idea to recall to function

void MainWindow::on_connectAction_clicked()
{
    openSerialPort(ui->serialPortInfoListBox->currentIndex());
}

I think it's not MVC

mrjj

@erytcg
Hi
Im not sure what you talk about.
MVC= model, view , controller?

Is there a question ?

What you mean recall ?
Do you open it in addAvailableSerialPorts ?

erytcg

Yes I talk about model, view , controller.
I add all avaibleports to vector in addAvailableSerialPorts ()
i open in openSerialPort(int index) / index=QComboBox->currentIndex();
and close in closeSerialPort(int index) / index=QListWidget->currentRow()+1;

and all works fine I think, but if I want show received data on QCustomPlot widget.
I don't know how to convert QByteArray to QVector<double>.
My received data from qDebug() - "\x0B"
Thanks a lot for help :)

mrjj

@erytcg
Nope a list of Class * is not really MVC.

Do you really need to convert QByteArray to QVector<double> ?
Why not convert to doubles when you read and add directly to QVector instead?

Also who sends the doubles? Its not trivial to send doubles over serial as they dont map
nicely to chars and there can be a difference in byteorder and precision loss.

erytcg

I need convert because QCustomPlot func need doubles

void 	addData (const QVector< double > &keys, const QVector< double > &values, bool alreadySorted=false)
or
void 	addData (double key, double value)

mrjj

@erytcg
Yes, i understand CustomPlot wants QVector<double> but i was wondering
instead of storing all values in ByteArray and then convert, if it would be more easy
to store directly in QVector when reading them off the serial port.

Anyway, how do u know how many indexes one double will take in ByteArray ?
double is normally 8 bytes (32 bit). Do you know the byte order from the sender?

mrjj

Hi
You can test with this sample
Uses QDataStream which should be good and fast.

int main(int argc, char *argv[])
{

QByteArray byteArray;

//generate ten random float value
QVector<float> v;
for (int i =0; i < 10;++i)
{
v << 100. * qrand()/RAND_MAX;
}
//ouput vector
qDebug() << v;

//write float value to array
{
QDataStream out (&byteArray,QIODevice::WriteOnly);
foreach(float f,v)
{
out << f;
}
}

//read all float from array
QVector<float> v2;
{
QDataStream in(byteArray);
while (!in.atEnd())
{
float f;
in >> f;
v2 << f;
}
}
//ouput vector
qDebug() << v2;

return 0;
}

From here
http://www.qtcentre.org/archive/index.php/t-24744.html

erytcg

Maybe I try explain what should my applications do. I send to device command for example: LB - measure temperature and I receive
AAAA, data is exchanged in ASCII format. Number is in Hex format. for example 0x075d. And I want add this received data to plot. And set interval between measurement.

jsulm

@erytcg You get double numbers as hex?! Is the double format used by this device clearly specified? I mean, you need to know how to convert those hex strings to doubles for that you need to know the format and byte order.