What Is USB Host Shield For Arduino Pro Mini? (Quick And Easy Guide) This is a USB Host Shield designed to be easily combined with the “Mini” variant of Arduino Board, specifically, Sparkfun 3.3V Arduino Pro Mini. It will also work with other 3.3V Arduinos. Also, due to its’ small size, it can be used as a general MAX3421E breakout board. This shield is fully compatible and supported by USB Host S