We're now at the point where USB attempts to start doing block I/O, but that's not working.

I've checked in my progress so far. To use it, grab the .atstart and open it in Atmel Start. Save the result as an Atmel Studio 7 project, then open it in Atmel Studio.

Next, add the bizarro workaround to the start of ResetHandler() in the startup code.

Now you have to change the CONF_USB_MSC_BULKIN_MAXPKSZ and CONF_USB_MSC_BULKOUT_MAXPKSZ constants from 0x40 to 0x200. They're located in usb_msc_config.h under Config.

Lastly, copy the .c and .h files into your project, overwriting any that may have been put there by Atmel Start. Don't forget to add them all to the project.

Rebuild the project and you're good to go.

If anyone can figure out what I'm doing wrong with the I/O transfer code, let me know.