METRO 328 ATmega328 (Fully Assembled) Adafruit METRO 328 ATmega328 (Fully Assembled) is an Arduino Uno R3 compatible and equivalent board, with a few extra Adafruit tweaks. Like the Uno R3, the METRO 328 is based on the 16MHz Microchip Technology ATmega328P 8-Bit AVR® Microcontroller, with 32KB of flash and 2KB of RAM. The METRO 328 also shares the same footprint of the Uno R3, and it is compatible with all R3 Arduino Uno compliant shields.