Adafruit METRO Mini is a derivative of the Arduino UNO board (RS 769-7409) and a scaled down version of the METRO (RS 124-5519). 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 20 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.

You can power the METRO Mini with a 6 V dc to 16 V dc PSU or by using the 5 V micro-USB connector. The METRO automagically switches between USB and DC.

Four indicator LEDs for easy debugging.

For projects where the board size is not important and you would prefer to have the headers pre-soldered onto the board there is the METRO board (RS 124-5519).

- ATmega328 microcontroller with Optiboot (UNO) Bootloader
- USB Programming and debugging via the well-supported genuine FTDI FT231X
- Input voltage: 6 V dc to 16 V dc (a 9 V dc power supply is recommended)
- 5 V onboard regulator with 150 mA out
- 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
- 32 KB Flash Memory, 0.5 K for bootloader, 31.5 KB available after bootloading
- 16 MHz Clock Speed
- 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