problem using QSerialPort
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Hi all -
I've got an app that uses a COM port for initial configuration of a device that then joins a Wifi network. I'm using the QSerialPort class for this configuration. I'm connecting a readyRead signal for input, but it never triggers. I'm also getting this error message:
serial port error QSerialPort::NoError encountered. QObject: Cannot create children for a parent that is in a different thread. (Parent is QSerialPort(0x16d13d8), parent's thread is QThread(0x161cb20), current thread is QThread(0x16e58d0)I'm wondering if I'm doing something wrong with my threads. Here's a code snippet:
int main(int argc, char *argv[]) { QApplication a(argc, argv); worker = new Worker(widget); thread = new QThread; worker->moveToThread(thread); widget->show(); thread->start(); rc = a.exec(); ... Worker::Worker(Widget *widget, QObject *parent) : QObject (parent) { m_serialPort = new SerialPort(this); ... SerialPort::SerialPort(QObject *parent) : QObject (parent) { QSerialPort m_serialPort; connect(&m_serialPort, &QSerialPort::readyRead, this, &SerialPort::readSerial);My slot SerialPort::readSerial() never gets called. I've verified that there's incoming data using a port monitor. Any ideas what I've done wrong here?
Thanks...
@mzimmers Is there a reason why you're using a thread? QSerialPort has an asynchronous API and there is usually no need to use threads for that.
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Hi all -
I've got an app that uses a COM port for initial configuration of a device that then joins a Wifi network. I'm using the QSerialPort class for this configuration. I'm connecting a readyRead signal for input, but it never triggers. I'm also getting this error message:
serial port error QSerialPort::NoError encountered. QObject: Cannot create children for a parent that is in a different thread. (Parent is QSerialPort(0x16d13d8), parent's thread is QThread(0x161cb20), current thread is QThread(0x16e58d0)I'm wondering if I'm doing something wrong with my threads. Here's a code snippet:
int main(int argc, char *argv[]) { QApplication a(argc, argv); worker = new Worker(widget); thread = new QThread; worker->moveToThread(thread); widget->show(); thread->start(); rc = a.exec(); ... Worker::Worker(Widget *widget, QObject *parent) : QObject (parent) { m_serialPort = new SerialPort(this); ... SerialPort::SerialPort(QObject *parent) : QObject (parent) { QSerialPort m_serialPort; connect(&m_serialPort, &QSerialPort::readyRead, this, &SerialPort::readSerial);My slot SerialPort::readSerial() never gets called. I've verified that there's incoming data using a port monitor. Any ideas what I've done wrong here?
Thanks...
@mzimmers said in problem using QSerialPort:
SerialPort::SerialPort(QObject *parent) : QObject (parent) { QSerialPort m_serialPort; connect(&m_serialPort, &QSerialPort::readyRead, this, &SerialPort::readSerial);This doesn't look right. Are you sure this is what you wrote?
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Hi all -
I've got an app that uses a COM port for initial configuration of a device that then joins a Wifi network. I'm using the QSerialPort class for this configuration. I'm connecting a readyRead signal for input, but it never triggers. I'm also getting this error message:
serial port error QSerialPort::NoError encountered. QObject: Cannot create children for a parent that is in a different thread. (Parent is QSerialPort(0x16d13d8), parent's thread is QThread(0x161cb20), current thread is QThread(0x16e58d0)I'm wondering if I'm doing something wrong with my threads. Here's a code snippet:
int main(int argc, char *argv[]) { QApplication a(argc, argv); worker = new Worker(widget); thread = new QThread; worker->moveToThread(thread); widget->show(); thread->start(); rc = a.exec(); ... Worker::Worker(Widget *widget, QObject *parent) : QObject (parent) { m_serialPort = new SerialPort(this); ... SerialPort::SerialPort(QObject *parent) : QObject (parent) { QSerialPort m_serialPort; connect(&m_serialPort, &QSerialPort::readyRead, this, &SerialPort::readSerial);My slot SerialPort::readSerial() never gets called. I've verified that there's incoming data using a port monitor. Any ideas what I've done wrong here?
Thanks...
@mzimmers
IIRC you're using a static build? so its probably not the latest Qt Version on what are you running?If it isn't the error @kshegunov pointed out
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@mzimmers Is there a reason why you're using a thread? QSerialPort has an asynchronous API and there is usually no need to use threads for that.
@jsulm I'm not using a thread exclusively for the serial port work; my worker thread essentially does all my non-UI stuff(encoding/decoding messages, etc.)
@kshegunov sorry; I was engaging in a bit of shorthand. m_serialPort is a member variable of SerialPort. The connect is correct, though.
@J-Hilk I'm currently using (non-static) 5.12.5.Last night it occurred to me that long ago, I'd come across a problem with transferring objects to new threads, in which some sub-objects don't get transferred properly.
I might try Dorfman's idea, though I'd prefer not to have to do that.
Thanks...
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@jsulm I'm not using a thread exclusively for the serial port work; my worker thread essentially does all my non-UI stuff(encoding/decoding messages, etc.)
@kshegunov sorry; I was engaging in a bit of shorthand. m_serialPort is a member variable of SerialPort. The connect is correct, though.
@J-Hilk I'm currently using (non-static) 5.12.5.Last night it occurred to me that long ago, I'd come across a problem with transferring objects to new threads, in which some sub-objects don't get transferred properly.
I might try Dorfman's idea, though I'd prefer not to have to do that.
Thanks...
@mzimmers said in problem using QSerialPort:
@J-Hilk I'm currently using (non-static) 5.12.5.
And there is your problem
https://bugreports.qt.io/browse/QTBUG-78086please update
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@mzimmers said in problem using QSerialPort:
@J-Hilk I'm currently using (non-static) 5.12.5.
And there is your problem
https://bugreports.qt.io/browse/QTBUG-78086please update
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Hi,
IIRC, your QSerialPort object won't get moved if your don't parent it.
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@mzimmers said in problem using QSerialPort:
Good eye. Thanks for catching that. I'll update immediately.
Any way, your initialization seems not correct to me:
SerialPort::SerialPort(QObject *parent) : QObject (parent) { QSerialPort m_serialPort; connect(&m_serialPort, &QSerialPort::readyRead, this, &SerialPort::readSerial); ... }should be, I think:
SerialPort::SerialPort(QObject *parent) : QObject (parent) , m_serialPort(new QSerialPort(this)) { connect(m_serialPort, &QSerialPort::readyRead, this, &SerialPort::readSerial); ... } -
@SGaist ah yes, that's what it was. Thanks for refreshing my memory.
Edit:
Which member variables does this apply to? For example, I also have a member QByteArray; does that need to be parented too?
Thanks...
@mzimmers said in problem using QSerialPort:
Which member variables does this apply to?
Each member which base class is QObject.
It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)
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@mzimmers said in problem using QSerialPort:
Which member variables does this apply to?
Each member which base class is QObject.
@KroMignon thanks...so a QByteArray object wouldn't be affected then.
It looks like the mechanics of updating have changed since I last used them. Is there a pre-built 5.14 for Windows available somewhere on github? EDIT: looks like the answer is "no;" I guess everyone builds their own now. Given my recent troubles trying to build a static Qt, I hope the directions in the 5.14 README are accurate.
I'm going to mark this solved, in anticipation that when I get a new Qt built, it'll work. Thanks for everyone's input on this.
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You need now to use your Qt account to access the pre-built binaries (the same you use to post here)
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You need now to use your Qt account to access the pre-built binaries (the same you use to post here)
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The bug tracker is your friend :-)
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