Amazon.com: WSDMAVIS 2 Pcs Mini MCU-Beetle USB Microcontroller ATMEGA32U4 Development Board for Arduino Leonardo : Electronics
Arduino Nano Micro-Controller with ATmega328P 16MHz 5.0V CH340G USB – Envistia Mall
Arduino Uno Rev3 — Arduino Online Shop
Using The Second Microcontroller On An Arduino | Hackaday
CH559 USB MCU Mini DEV Board [CH55x Series] – ElectroDragon
Amazon.com: SparkFun Qwiic Pro Micro - USB-C (ATmega32U4) - Compatible with Arduino development board 5V/16MHz microcontroller AP2112 3.3V Voltage Regulator Castellated PTH pin pads Reset button Maximum 6V input : Electronics
Amazon.com: Aihjcnele Attiny85 Digispark Kickstarter USB Module Development Board Compatible IDE for Arduino General Micro USB MCU Development Module Compatible with UNO R3 PWM I2C SPI ADC I/O with Cable Wire :