Adafruit's pro trinket was designed with 18 GPIO, two extra analog inputs, 28 K of flash, and 2 K of RAM. Because sometimes, you just need more of everything. This board has USB bootloading support using a Micro-USB jack. We also added Optiboot support, so you can either program your pro trinket over USB or with a FTDI cable. The pro trinket PCB measures only 1.5" x 0.7" x 0.2" (without headers) but packs much of the same capability as an Arduino UNO. So it's great once you've finished up a prototype on an official Arduino UNO and want to make the project smaller.

The pro trinket 5 V uses the Atmega328P chip, which is the same core chip in the Arduino UNO, Duemilanove, or Mini at the same speed and voltage. So you'll be happy to hear that not only is the pro trinket programmable using the Arduino IDE as you already set up, but 99% of Arduino projects will work out of the box.

Features

• ATmega328P on-board chip in QFN package
• 16 MHz clock rate, 28 K flash available
• USB bootloader with a nice LED indicator looks just like a USBtinyISP so you can program it with AVRdude and/or the Arduino IDE (with a few simple configuration modifications)
• Also has headers for an FTDI port for reprogramming
• Micro-USB jack for power and/or USB uploading, you can put it in a box or tape it up and use any USB cable for when you want to reprogram
• On-board 5.0 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
• Power with either USB or external output (such as a battery) - it will automatically switch over
• On-board green power LED and red pin #13 LED
• Reset button for entering the bootloader or restarting the program
• Works with 99% of existing Arduino sketches (anything that doesn't use more than 28 K, and doesn't require pins #2 and #7)