Hi
To avoid complications at the PC side consider using CDC class (Communication Device Class) since this allows the device to be seen as a virtual COM port and any PC code that you have that can read data coming in from a COM port will be compatible with it coming in over the virtual COM port (USB device) [using the COM port on the PC is very simple]. If you make a new (custom) class you may spend more time on trying to get it working (or end up having to buy an expensive driver from one of the PC USB driver specialists) on the PC side than it is worth (notice that the majority of PC drivers for embedded 'things' - including some freescale debuggers, come from Jungo; developing such a PC USB device driver for such things is quite a specialist task and that is why they can also command quite high prices for their products). The CDC driver come as part of Windows and so makes life easier - even if people will explain that it is not very good; it serves the purpose in most projects.
This also allows you to make a first application which feeds the data from the board via a UART. This will not be as fast as USB (eg. 115k rather than about 10Mb/s) but, once it works, you can 'simply' switch the UART handle over to the USB handle and it will work the same (on Kinetis and on the PC) but with the final higher data rate.
There are some ideas about USB device CDC here: http://www.utasker.com/docs/uTasker/USB_User_Guide.PDF
This solution allows the USB interface to look like a UART interface from the point of view of the embedded SW (thus switching between UART and USB is as simple as setting the interface handle variable with the interface handle to be used (it is also true for TELNET when working with a K60, which would allow either UART, USB or TCP for the transfer - or a mixture of them).
Regards
Mark
