Here’s a Multi-Protocol Synchronous Serial Engine (MPSSE) implementation from FTDI.
This application note gives an example of using the Multi-Protocol Synchronous Serial Engine (MPSSE) on the FT232H device. It uses D2xx commands to configure the MPSSE to interface with two Analog to Digital Converters (ADCs) using the Serial Peripheral Interface (SPI). It is controlled by software running on the PC written in Visual Basic 2008.
Ummm… I don’t get it. Just use a USB capable micro-controller with on board A//D’s and around 90 percent of the parts used in this app note go away.