Datasheet

something, like charging a battery, or if you need more than 150mA of current (this pin
can supply 500mA+ from USB ports) or to detect when the Pro Trinket is plugged into
USB, this pin will have 5V power on it if and only if its plugged into something via the
mini B connector
GND is the common ground pin, used for logic and power. It is connected to the USB
ground and the power regulator, etc. This is the pin you'll want to use for any and all
ground connections
GPIO Pins
Next we will cover the 18 GPIO (General Purpose Input Ouput) pins! 18 GPIO is a big step up
from the little Trinket with only 5 or so pins. This is almost as many as a 'full grown' Arduino.
In fact, since the Pro Trinket uses the same core chip as an Arduino, nearly any existing
project that uses special pins like hardware PWM or SPI will work 'out of the box'.
All the GPIO pins can be used as digital inputs, digital outputs, for LEDs, buttons and switches
etc. They can provide up to 20mA of current. Don't connect a motor or other high-power
component directly to the pins! Instead, use a transistor to power the DC motor
on/off (http://adafru.it/aUD)
Logic Level
On a 3V Pro Trinket, the GPIO are 3.3V output level, and should not be used with 5V inputs.
On a 5V Pro Trinket, the GPIO are 5V output level, and can be used with 3V inputs but may
damage electronic devices that are 3V input only!
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