Just to be clear, your original code would have worked. You just needed to set your string control to show \codes. You probably had it set for normal mode, and thus were sending AT backslash r backslash r. If it was set for \codes and you entered AT\r\n, then LabVIEW would have known you were have known you were trying to send carriage return and linefeed instead of the literal characters of backslashes "r" and "n".
