[SOLVED]Serial port not sending bytes in my application
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[quote author="toptan" date="1363098990"]You probably need to read docs for your LCD more thoroughly. I doubt that sending single letter via serial will cause the display to display that letter.[/quote]
The external device is working correctly. Trust me, I'm not sending single letters to an OLED display :-)
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Have you checked whether putChar returns true. After all it is QIODevice of some king. Also you could try write and waitForBytesWritten combo. Something like this:
@
QByteArray data("W");
serial.write(data);
if (!serial.waitForBytesWritten(waitTimeout)) {
/* timeout handling */
}
@I am using array of six 7 segment led displays in my project and QSerialPort works no problem on linux.
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2 JustGreg
Remove serial->close() in end of MainWindow constructor.
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[quote author="kuzulis" date="1363101362"]2 JustGreg
Remove serial->close() in end of MainWindow constructor.[/quote]
Thank you kuzulis. That was the problem, however my app is still not sending the bytes when I'm stepping over the code in debug mode. Only in 'Run' mode. Do you know what can cause this behaviour? It'd be nice to know.
@toptan: the putChar method returned true, even in debug mode where there were no bytes sent to my device...strange. Thank you for your help, anyway.
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bq. That was the problem, however my app is still not sending the bytes when I’m stepping over the code in debug mode. Only in ‘Run’ mode. Do you know what can cause this behaviour? It’d be nice to know.
Because all I/O operations processing asynchronously in Qt event-loop, so in debug step-by-step event-loop is stopped by step-by-step. :)
So, nothing strange in this...
UPD:
Also, port->write() always returns true, because it write data to internal ring buffer.
So, for catch errors you can connect to SerialPortError signal. -
[quote author="toptan" date="1363102507"]No problem. I also have the problem in debug mode. I overcame that with a lot of qDebug(), if you find solution for step-by-step debugging please share.[/quote]
Right, I'll check qDebug then. I'm new to Qt & Linux so do not expect too much brainpower from me :-)
[quote author="kuzulis" date="1363102625"]
Because all I/O operations processing asynchronously in Qt event-loop, so in debug step-by-step event-loop is stopped by step-by-step. :)So, nothing strange in this...[/quote]
Good to know. Thank you and I'll be back soon with my receive event signal-slot questions :-)
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[quote author="kuzulis" date="1363101362"]2 JustGreg
Remove serial->close() in end of MainWindow constructor.[/quote]
One more question: what could cause the putChar process to fail? The close method was too fast and it had already closed the port before the internal buffer was emptied?
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Yes. At the moment to the call close() does not force flush data.
So, you can do port->flush() before port->close()
UPD: On future maybe behavior can change... and flush() will called automatically on close().