how to open the serial port of my pc from the qt app

[ChrisW67]

There are two possibilities straight from the error message:

• Attempting to open an already opened device by another process. If there is another process with the port already open then this might happen. Minicom should not be running when you try to run this.
• User not having enough permission and credentials to open. The permissions are those of the file representing the serial port: probably "/dev/ttyS0" but it may be in a subdirectory of /dev. Often only root and a group called "uucp" have write access to the device.
  

  $ ls -l /dev/ttyS0
  crw-rw---- 1 root uucp 4, 64 Feb 27 07:15 /dev/ttyS0
  $ groups
  wheel audio cdrom video games cdrw users wireshark vboxusers truecrypt uucp

  $ ls -l /dev/ttyS0
  crw-rw---- 1 root uucp 4, 64 Feb 27 07:15 /dev/ttyS0
  $ groups
  wheel audio cdrom video games cdrw users wireshark vboxusers truecrypt uucp

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  Your Linux user should be generally placed in the "uucp" group (recommended) although you can alter the serial port permissions directly (not recommended).

Here is a User Management tutorial.
Here is a Linux File Permissions tutorial.

[prasad1001]

Thanks for the quick reply sir,
First of all sorry for my english.

I was running my code in 'root' and it is getting data from serial port....
I written the code for reading data as shown below,
Qt code:

if(port->waitForReadyRead(5000)){
QByteArray readdata=port->readAll();
//textEdit->append(readdata);
while(port->waitForReadyRead(1000)){
readdata +=port->readAll();
}

textEdit->append(readdata);
}

It is reading one time and displaying on the textEdit.. but i want to monitor and read the data from the port continuously whenever the data available...what should i have to do...
Thanks in advance...

[anda_skoa]

Don't "wait for readyRead", connect a slot to the readyRead() signal and read the data in the slot.

Btw, running a GUI program as root is usually a bad idea. At some point you should invest a bit of time to get the permissions right for a normal user account.

Cheers,
_