Data was shifted when i use UART

Hi everyone,

I make a GUI and send a string contains 4 bits,

The first time i send ( E.g "1234") I have received "1234"

But the 2nd i have received "2341", so on the third i have received "3412"

So data was shifted, I have debugged and detected in my received string have a char with value ="10" (LF), Although i havent send it.

How can i fix my error?

Plz give a solution, thank in advance.