There are many times within guiDesigner where you may need to enter hex data. Some examples include:
When entering hex data in guiDesigner, it should always be entered in \xFF
format, where FF is the hex character you want to send.
Some common hex characters used are:
\x0D
\x0A
For a listing of common hex character codes, please see the below chart (thanks to http://www.lookuptables.com)