Q: 

Do you have any USB drivers for the EFM32 parts?

A:

Yes, as a part of the CMSIS package (available in Simplicity Studio and as a separate download here), we distribute a host and device library for the USB peripheral in the EFM32. The Board Support Packages (Simplicity Studio and separate download here) for the kits that support USB, comes with several USB host and device examples including mass storage, human interface and communication class.