The Adafruit METRO is an Arduino Uno equivalent board designed with a few extra features to improve upon the original Uno. Adafruit wanted to use their years of experience playing around with AVR based microcontrollers to build a development board that was easy to use and hacker friendly.

At the heart is an ATmega328P, with 32KB of flash and 2KB of RAM, running at 16MHz; this is the same chip used by the Arduino Uno. The overall footprint is also the same as the Uno, and is compatible with all R3 Arduino Uno compliant shields out there.

Since the METRO uses the ATmega328P chipset, it features 19 GPIO pins, 6 of which are Analog in as well, and 2 of which are reserved for the USB-serial converter. There’s also 6 PWMs available on 3 timers (1 x 16-bit, 2 x 8-bit). There’s a hardware SPI port, hardware I2C port and hardware UART to USB. Logic level is 5V but by cutting and soldering closed a jumper, you can easily convert it to 3.3V logic.

The Adafruit METRO is programmed with the standard Arduino Development Environment (IDE) using a micro USB cable. The USB receiving connector used by this cable is much shorter and results in less issues with clearance for non-standard shields. Onboard Adafruit has also added an On/Off slide switch so it can be plugged in and turned off. The USB / Serial conversion is handled by a genuine CP2104 chipset, rather than a secondary USB native microcontroller.

All in all, this is a great alternative to the standard Arduino Uno!