Can you check my Atmega32u4 schematic ? - Microcontrollers - Arduino Forum
Amazon.com: CoCocina Teensy 2.0 Compatible USB Avr Development Board for Isp Atmega32U4 Geekcreit for Arduino - Products That Work with Official Arduino Boards : Electronics
ATMEGA32U4 Microcontroller: Pinout, Datasheet and Equivalents
Addicore Pro Micro ATmega32U4 (Arduino Clone)
AVR Programming with Adafruit's Atmega32u4 · open collector