Adafruit METRO 328

Adafruit METRO 328 is easy to use and hacker-friendly. It has an ATmega328 at the heart with 32KB of flash and 2KB of RAM running at 16MHz. Versions of the METRO 328 come as a fully assembled and tested development board with or without headers attached. Four rubber bumpers are included to keep it from slipping off a desk.

Features

ATmega328 brains: 32KB of flash (1/2K reserved for the bootloader), 2KB of RAM, clocked at 16MHz.
Power the METRO with 7-9V polarity protected DC or the micro USB connector to any 5V USB source. The 2.1mm DC jack has an on/off switch and the METRO will automatically switch between USB and DC.
METRO has 20 GPIO pins, 6 of which are Analog, 2 are reserved for the USB-serial converter. 6 PWMs are available on 3 timers (1x16-bit, 2x8-bit). There's a hardware SPI port, hardware I²C port, and hardware UART to USB.
GPIO Logic level is 5V but by cutting and soldering closed a jumper, you can easily convert it to 3.3V logic.

USB to Serial converter can be used by any computer to listen/send data to the METRO and can launch and update code via the bootloader.
Four indicator LEDs, on the front edge of the PCB, for easy debugging. A green power LED, 2 RX/TX LEDs for the UART, and a red LED connected to pin PB.
Easy reprogramming, comes preloaded with the Optiboot bootloader, supported by avrdude, and only uses 512 bytes.
Beautiful styling by PaintYourDragon and Bruce Yan, in Adafruit Black with gold, plated pads. Works with all Adafruit designed shields.

Technical Information

ATmega328 microcontroller with Optiboot (UNO) Bootloader
USB Programming and debugging via the well-supported genuine FTDI FT231X
Input voltage: 7-9V (a 9VDC power supply is recommended)
5V logic with 3.3V compatible inputs can be converted to a 3.3V logic operation
20 Digital I/O Pins: 6 are also PWM outputs and 6 are also Analog Inputs
32KB Flash Memory - 0.5K for bootloader, 31.5KB available after bootloading

6-pin ICSP Header for reprogramming
16MHz Clock Speed
Compatible with "Classic" and "R3" Shields
Adafruit Black PCB with gold plate on pads
53x68.5mm / 2.1x2.7"
Height (w/ barrel jack): 13mm / 0.5"
Weight: 16.5g
Derivative of "Arduino UNO R3 Reference design"
Open-source hardware files on Github

METRO Mini 328

Adafruit METRO Mini 328 has USB-to-serial built-in and is used for smaller projects. The METRO Mini 328 is a tiny, breadboard-friendly development board that is easy to use and hacker-friendly. Metro Mini can be programmed with the Arduino IDE.

The Metro Mini comes as a fully assembled and tested board, with bootloader burned in and also a stick of 0.1" header. Some light soldering is required if you'd like to plug it into a breadboard, or you can solder wires or header directly to the breakout pads. Once headers are installed they can be fitted into 0.6" wide sockets.

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