If you must isolate a device that also connects to a PC, the Universal Serial Bus (USB) interface is a natural choice. USB’s extensive industry support and simple structure (there are only four wires in a USB cable) make it a popular PC interface. A USB controller that attaches to your embedded system using the SPI interface is easy to electrically isolate.

This paper describes why the MAX3420E USB peripheral controller with SPI interface provides an ideal method for adding USB functionality to an embedded system.