FYSETC USB Host Adapter 3421 V1.1 for Malin 2.0 3D printer mainboard EXP2A EXP2B based on the MAX3421E from Maxim Integrated 1.1 Introduction The FYSETC USB Host Adapter 3421 allows you to connect a USB device to your board(For 3D printer applications, you can use a USB flash drive, and marlin has already perfectly supported it.).The moudle is based on the MAX3421E from Maxim Integrated , which is a USB peripheral/host controller containing the digital logic and analog circuitry necessary to implement a full-speed USB peripheral or a full-/low-speed host compliant to USB specification rev 2.0. In particular, two sockets (EXP2A & EXP2B) are provided for the 3D printer motherboard, one for the knob on the display, and one for MAX3421 SPI communication. which means you can quickly connect it to your board without affecting the other device. 1.2 Summary Operating Voltage: 5V USB Controller: MAX3421E Max Current: 500mA Size: 51.3 x 22.3mm