Level shifter
Build your own
To be able to debug LibXenon / XeLL stuff you want most likely a LVTTL, here is how you build one:
You need:
1x MAX3232 IC
5x 0,1uF Caps
1x 9-pin D-Sub Port
Solder all according to this picture.
Now you just hook it up like on the diagram showed on this page: Serial Console