The atmel code is (I think) this one
https://github.com/ks156/WeIODuino.
SFPStream description can be found in the code.
We used USB2640 hub from Microchip, however it is not needed. We added it only to have an additional USB slot. Communications on UPER1 is done via USB CDC protocol, so usb cdc drivers is the only thing that you need on Carambola2, however they may already be installed by default (I don't remember exactly).