Let me take you on a tour of your Gemma! Each Gemma is assembled here at Adafruit and comes chock-full of good design to make it a joy to use.

• Mini-B USB connector (on Version 1) - We went with the tried and true mini-B USB connector for power and/or USB bootloading on our first version of the Gemma
• Green Power LED - you'll know that the board is powered up when this bright LED is lit
• Red #1 LED - this LED does double duty. Its connected with a series resistor to the digital #1 GPIO pin. It pulses nicely when the Gemma is in bootloader mode, and its also handy for when you want an indicator LED.
• JST Battery Input - take your Gemma anywhere and power it from an external battery. This pin can take up 16V DC input, and has reverse-polarity, over-curent and thermal protections. The circuitry inside will use either the battery or USB power, safely switching from one to the other. If both are connected, it will use whichever has the higher voltage. Works great with a Lithium Polymer battery or our 3xAAA battery packs with a JST connector on the end
• Voltage Output - This pin will give you either the battery power or USB power, whichever has a higher voltage. Its great when you want to power something like NeoPixels, that might use more than the 150mA available from the onboard regulator
• 3V Regulator Out - The on-board voltage regulator can supply up to 150mA at a steady 3.3V from up to 16VDC
• Sewing friendly pads - You can easily sew to these pads, and they're gold plated so they wont corrode (oxidize). You can also use alligator clips or solder directly to them.
• GPIO! - 3 GPIO pins, at 3V logic, check the next section for a detailed pinout guide
• Reset Button - an onboard reset button will launch the bootloader when pressed and the Gemma is plugged into a computer. If it is not connected to a computer, it's smart enough to go straight to the program.

New in Version 2

• Micro-B USB connector (on Version 2) - In version 2 we upgraded to a micro USB connector, which is now the standard for all cell phones and other devices. It is used for power and/or USB bootloading on our first version of the Gemma
• On/Off switch (in version 2 only) - With the space we saved by moving to a smaller chip and micro USB connector we had enough space to add an on/off slide switch!