16u2 USB2Serial for Arduino DUE


I am working in a project with a ATSAM3x8E microcontroller (like a Arduino due), but my USB interface is not working (because the differential pair wrong design), and I would like to test it with a normal sketch via UART, but I have no 16u2 microcontroller, then I have thought to use the 32u4 microcontroller (arduino leonardo). I have found this repository with 16u2 firmware: https://github.com/arduino/Arduino/tree/master/hardware/arduino/sam/firmwares/atmega16u2
But I need the source to make it work with the 32u4 microcontroller.

Thanks a lot.

Can anyone help me, please?