While Adafruit Trinket is good for small projects, if you need more capability with a slightly larger yet small form factor, Adafruit Pro Trinket is just the right choice. It has more powerful ATMega 328 chip(Similar to ones used in Arduino boards) with 18 GPIOs, 28K flash and 2K of RAM.
Like the Trinket, Pro Trinket also comes in 2 variations 5V logic and 3V logic. It has onboard USB bootloading support using Micro USB port. Also it ha Optiboot support, so you can either program your Pro Trinket over USB or with a FTDI cable just like the Pro Mini and friends.
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 3V uses the Atmega328P chip, which is the same core chip in the Arduino UNO/Duemilanove/Mini/etc. However, it uses 3V logic and 12MHz clock which means it's good when you want a lower-power and lower-voltage setup. Pro Trinket is programmable using the Arduino IDE as you already set up, and 95% of Arduino projects will work out of the box!
|Microcontroller||atmel ATmega328P (QFP package)|
|Operating Voltage||3.3V DC|
|Input Voltage (Limits)||3 to 16V DC|
|Digital I/O Pins||12 (of which 6 provide PWM output)|
|Analog Input Pins||8|
|Flash Memory||32 KB (ATmega328P) of which 4 KB used by bootloader|
|EEPROM||1 KB (ATmega328P)|
|SRAM||2 KB (ATmega328P)|
|Clock Speed||12 MHz|
|USB||Micro USB for power or uploading new code only|
|Power Supply||Micro USB or external output (battery or power supply) - automatic switching|
|Dimensions||38 x 18 x 2 mm|