“We wanted to design a microcontroller board that was small enough to fit into any project, and low cost enough to use without hesitation,” Adafruit’s Limor Fried (aka LadyAda) explained in a recent blog post. “Gemma is perfect for when you don’t want to give up your Flora and aren’t willing to take apart the project you worked so hard to design. It’s our lowest-cost sewable controller!”
Fried described the Attiny85 as a “fun processor” because despite being so small, the device boasts 8K of flash and 5 I/O pins, including analog inputs and PWM ‘analog’ outputs.
“We designed a USB bootloader so you can plug it into any computer and reprogram it over a USB port just like an Arduino (it uses 2 of the 5 I/O pins, leaving you with 3),” Fried continued. “In fact we even made some simple modifications to the Arduino IDE so that it works like a mini-Flora. Perfect for small and simple projects – the Gemma will be your go-to wearable electronics platform.”
In addition to Atmel’s ATtiny85, key hardware specs include:
- 1.1″ / 28mm diameter and 0.28″ / 7mm thick.
- Easy-to-sew or solder pads for embedding in wearable projects.
- 8K of flash, 512 byte of SRAM, 512 bytes of EEPROM.
- Internal oscillator runs at 8MHz.
- Ultra low power, only 9 mA while running.
- USB bootloader with LED indicator programmable with the Arduino IDE
- Mini-USB jack for power and/or USB uploading
- Rugged and foolproof bootloader process
- ~5.25K bytes available for use (2.75K taken for the bootloader)
- On-board 3.3V or 5.0V power regulator with 150mA output capability and ultra-low dropout.
- Up to 16V input, reverse-polarity protection, thermal and current-limit protection.
- Power with either USB or external output (such as a battery) – it’ll automatically switch over
- 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 IO pins have 1 analog input and 2 PWM output as well.
- Hardware I2C capability for breakout and sensor interfacing.
Interested in learning more about Adafruit’s Gemma? You can check out LadyAda’s detailed Gemma tutorial here.