Merging Arduino Pro Micro and USB Host Tiny 2.0 - Project Guidance - Arduino Forum
Micro/mini/type-c Usb Atmega32u4 Module 5v 16mhz Board For Arduino Atmega32u4-au/mu Controller Pro-micro Replace Pro Mini - Integrated Circuits - AliExpress
transistors - Questions about the circuit of the Arduino Micro - Electrical Engineering Stack Exchange