SPI Storm serial protocol host adapter from Byte Paradigm supports both quad-/dual-SPI protocols. Controllable via USB interfaces, it accesses ASICs, SoCs, FPGAs, and other serial systems at ...

Microchip's HID-class MCP2210 USB to SPI protocol converter is the simplest, smallest-footprint and most cost-effective option for adding USB-Certified connectivity to SPI-based systems.

The good news is that the ATmega168 chips being used have a built-in interrupt based SPI protocol.