Problem>QT and Mini2440: Get text from Line edit

[mrquicuong]

Hi there,
My project uses QtDesigner to create a GUI for Kit Mini2440. It has a Line edit box to receive texts from user and send them via UART. All project was built without error and downloaded to the Mini2440 successfully.
But, when I press SEND button to send texts in this box "Line edit", I got the message "[name of project] was terminated due to application error (11)".
This is my code to change get text and send them:
I use library "terminos.h" for UART

QString text="";
          text=text_setspeed->text(); //text_setspeed is the name of the Line edit
          write(fd,text.latin1(),text.length()); 
          // But if I code like this, it has no error:
          QString text="abc"; 
          write(fd,text.latin1(),text.length());

QString text="";
          text=text_setspeed->text(); //text_setspeed is the name of the Line edit
          write(fd,text.latin1(),text.length()); 
          // But if I code like this, it has no error:
          QString text="abc"; 
          write(fd,text.latin1(),text.length());

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I guess I has problem when change type of variable from Qstring >> char * by "text.latin1()". Because the function write() is defined as: write(fd, data, n_bytes);
with char *data and int n_bytes.
Ps: I attached my project.test5.zip
Thank you in advance.