Hi Dario,
To enable the UART messages you would need to enable first the debug mode.
In the proyect properties -> C/C++ Build-> Settings ->Preprocessor. Add a new define that says :"DEBUG_ENABLE" with this you will enable the UART commands. Do the same in the lpc_board_nxp_lpcxpresso_1347 project.

If you want to see it in a terminal console in your PC, connect an USB to serial in the P0_19 and P0_18. With this you will see the DEBUGSTR in the console.
I hope this can hep you.
Best Regards,
Alexis Andalon