Adafruit Gemma V2 - Miniature Wearable Electronic Platform

Part number: 1222
Description
If you’ve never heard of GEMMA before, it’s a mini wearable platform based on a circular 1.1 inch (2.8 cm) diameter board. Although it was designed for wearable applications, its affordability and dinky size make it great for all kinds of exciting portable projects.It’s a doddle to programme too with an Arduino IDE over USB, and the central microcontroller is the Atmel Attiny85 8-bit MCU.
Actually, this version of GEMMA is the second generation, though you’ll find it pretty much identical to the original. The main difference is the On-Off switch and the Micro-B USB connector.
The Attiny85 processor boasts 8K of flash and 5 I/O pins – including analogue inputs and PWM outputs. You’ll find a USB bootloader from Adafruit.com. But please note – though you can program GEMMA with the Arduino IDE, this little platform isn’t 100% Arduino compatible.