I am currently developing a "dual boot" for the 16U2 based in LUFA, what I have is a program that reads the MOSI pin of the 16U2 when started and if it is at a LOW level it starts a USB-Serial communication but if it is HIGH is starts a USB-MIDI communication.
That switching works perfect, the computer recognizes the two diferent situations(a COM port when LOW and an Audio Controller when a HIGH), the MIDI communication works well also, but the problem is that the Serial communication doesn't.
It looks like there is a problem when it initializes it, I want to have a serial communication with a Visual Studio c# app that I have build but when I try to connect the app with the 16U2, Visual Studio teports an error at the port opening function. I have tried with the same PCB, but the factory firmware(Arduino USB-Serial) and it works correctly, so thats my point that the thing that isn't working correctly is my LUFA firmware.
It is based on LUFA 140928, here I upload the full folder, where I have my project is on \lufa-LUFA-140928\Projects\arduino_midi
Thank you so much in advance