Adafruit METRO is a derivative of the Arduino UNO board (RS 769-7409) so you can find plenty of projects and example code to use and adapt. Running the ATmega328P at 16 MHz with 32 KB of flash and 2 KB of RAM it is perfect for most simple projects. There are 19 GPIO pins including analogue inputs, hardware UART, SPI and I²C, timers and PWM. Logic level is 5 V but it can easily be converted it to 3.3 V.

Headers are assembled and soldered on for you and the board is fully tested.

You can power the METRO with 7 V dc to 9 V dc PSU via the 2.1 mm DC jack which has an on/off switch next to it. Alternatively you can power it by using the 5 V micro-USB connector. The METRO automagically switches between USB and DC.

Compatible with all Adafruit shields which stack directly on top to add specific features. The Metro is shown with a 12 button capacitive touch shield attached to demonstrate how it fits together with shields but is not included. Four indicator LEDs are on the front edge of the board for easy debugging even with a shield on top.

For projects where the board size is important, there is the scaled down METRO Mini board (RS 124-5512).

- ATmega328 microcontroller with Optiboot (UNO) Bootloader
- USB Programming and debugging via the well-supported genuine FTDI FT231X
- Input voltage: 7 V dc to 9 V dc (a 9 V dc power supply is recommended)
- 5 V regulator can supply peak ∼800 mA as long as the die temp of the regulator does not exceed 150°C
- 3.3 V regulator can supply peak ∼150 mA as long as the die temp of the regulator does not exceed 150°C
- 5 V logic with 3.3 V compatible inputs
- 20 Digital I/O Pins: 6 are also PWM outputs and 6 are also Analogue Inputs
- 6-pin ICSP Header for reprogramming
- 32 KB Flash Memory, 0.5 K for bootloader, 31.5 KB available after bootloading
- 16 MHz Clock Speed
- Compatible with "Classic" and "R3" Shields
- Supplied with 4 rubber bumpers
- 53 x 71 x 13 mm / 2.1" x 2.8" x 0.5”
- Weight: 19 g

If you use a Mac or Windows, then install the FTDI VCP drivers from FTDI to make the COM/Serial port show up correctly.

Adafruit METRO ATmega328 Development Boards