The bootloader does not affect RAM usage. The bootloader on the Pro Trinket uses 4KB of FLASH so the maximum sketch size is 28,672 bytes.The USB connection is for uploading new code only. This is to keep the Pro Trinket small and inexpensive, you can use any FTDI cable to connect to the FTDI port for a Serial connection. There is no Serial-to-USB chip onboard.You cannot plug shields directly into the Pro Trinket.The onboard 5V regulator can provide 150mA output, not 800mA out.Pins #2 and #7 are not available (they are exclusively for USB).Here's some things you may have to consider when adapting Arduino sketches: So you'll be happy to hear that not only is Pro Trinket programmable using the Arduino IDE as you already set up, but 99% of Arduino projects will work out of the box! The Pro Trinket 5V uses the Atmega328P chip, which is the same core chip in the Arduino UNO/Duemilanove/Mini/etc. 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 PCB measures only 1.5' x 0.7' x 0.2' (without headers) but packs much of the same capability as an Arduino UNO. Note: You will need a USB micro B cable to power and to program this board, so grab this cable here if you don't have one. Adafruit also added Optiboot support, so you can either program your Pro Trinket over USB or with an FTDI cable just like the PRO Mini using UC00A or UC00C. Like the Trinket, it has onboard USB bootloading support - Adafruit opted for a MicroUSB jack this time. That's why Adafruit designed Pro Trinket, with 18 GPIO, 2 extra analog inputs, 28K of flash, and 2K of RAM. While it has been great to see tons of tiny projects, sometimes you just need more pins, more FLASH, and more RAM. It's like an Arduino Pro Mini with more pins and USB tossed in, so delicious. Trinket's got a big sister in town - the Pro Trinket 5V! Pro Trinket combines everything you love about Trinket with the familiarity of the common core Arduino chip, the ATmega328. please take EXTRA PRECAUTION while doing soldering works.

Note:This board comes with loose headers, so soldering is required. Lithium Ion Rechargeable Battery and Charger.

Adafruit trinket 5v tutorial