Sketch from https://petervanhoyweghen.wordpress.com/2012/11/08/using-the-leonardo-as-usb-to-serial-converter/ to create usb to serial converter from Arduino Leonard / Teensy
Replaced with sketch from Arduino discussion arduino/Arduino#3343
Leonardo pinouts:
- USB - USB in/out
- RX pin 0 -> RX (connect to TX pin on remote device)
- TX pin 1 -> TX (connect to RX pin on remote device)