GEMMA is a tiny wearable platform built on a round 1.1 inch (2.8 cm) diameter board. The microcontroller at the heart of GEMMA is the Atmel Attiny85 8-bit MCU and is programmable with an Arduino IDE over USB.

This, the second generation of GEMMA, is physically and code-wise identical to the original but now has a Micro-B USB connector and an On-Off switch. It was designed mainly for wearable applications but its small size and low cost makes it great for a wide range of portable projects.

The Attiny85 processor has 8K of flash and 5 I/O pins, including analogue inputs and PWM outputs. There is a USB bootloader available from Adafruit.com but although you can program GEMMA using the Arduino IDE, it is not fully 100% Arduino compatible.

- Super small, only 1.1" / 28 mm diameter and 0.28" / 7mm thick.
- Easy-to-sew or solder pads for embedding in your wearable project
- ATtiny85 on-board, 8K of flash with around 5.25K bytes available for use (2.75K taken for the bootloader)
- 512 bytes of SRAM, 512 bytes of EEPROM
- Internal oscillator runs at 8 MHz
- Ultra low power, draws only 9 mA while running
- Micro-USB jack for power and/or USB uploading
- On-board 3.3 V power regulator with 150 mA output capability and ultra-low dropout. Up to 16 V input, reverse-polarity protection, thermal and current-limit protection.
- On-board green power LED and red pin #1 LED
- Reset button for entering the bootloader or restarting the program.
- 3 GPIO - The 3 independent I/O pins have 1 analogue input and 2 PWM output as well.
- Hardware I²C capability for breakout & sensor interfacing.

Adafruit GEMMA Wearable Platform