This is the Adafruit METRO Arduino-Compatible - with headers. It's a fully assembled and tested microcontroller and physical computing board with through-hole headers attached. If you don't want a Metro with the headers attached for super-slimness, check out our Metro without Headers.
The METRO works great with the Arduino IDE, and runs the ATmega328P at 16MHz so it is shape and pin-compatible with Arduino UNO R3 shields and boards. You can use this with the Arduino IDE (both desktop and cloud version) by selecting 'Arduino UNO' in the Boards menu.
We sure love the ATmega328 here at Adafruit, and we use them a lot for our own projects. The processor has plenty of GPIO, Analog inputs, hardware UART SPI and I2C, timers and PWM galore - just enough for most simple projects. When we need to go small, we use a Metro Mini or a Trinket M0, but when size isn't as much of a concern, we reach for an Adafruit METRO.
METRO is the culmination of years of playing with AVRs: we wanted to make a development board that is easy to use and is hacker friendly. At the heart is an ATmega328P, with 32KB of flash and 2KB of RAM, running at 16 MHz. It comes with the Optiboot bootloader already installed, and is Arduino IDE compatible.
Technical Details