Free obd II interface audi A6 software?

I have got an OBD 2 interface for my vectra called rohs op-com diagnostic interface it worked great on my vectra and wife's astra and corsa d but i crashed my vectra and now i bought an audi A6 2.0 tdi on a 57 plate UK and need the software to use on my pc to talk to my car it is USB based and does fit in car just cant talk to car it must be free please as i bought the interface mant thanks i know you guys wont let me down