Datasheet

Power Pins
We'll start with the top pins BAT+ and USB+ and GND
BAT+ is the Battery + Input pin. If you want to power the trinket from a battery or power
adapter or solar panel or any other kind of power source, connect the + (positive) pin here!
You can connect up to 16V DC. If you have a 3V Trinket, you'll want at least 3.5V input to get
a good 3.3V output. If you have a 5V trinket, 5.5V or higher is suggested. This input is
reverse-polarity protected.
USB+ is the USB + Output pin. If you want to use the USB 5V power for 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 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 5 GPIO (General Purpose Input Ouput) pins! For reference you may want to
also check out the datasheet-reference above for the core ATtiny85 pin
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)
On a 3V Trinket, the GPIO are 3.3V output level, and should not be used with 5V inputs. On a 5V
Trinket, the GPIO are 5V output level, and can be used with 3V inputs but may damage electronic
devices that are 3V input only!
The first 3 pins are completely 'free' pins, they are not used by the USB connection so you never
have to worry about the USB interface interfering with them when programming
GPIO #0 - this is connected to PB0 on the ATtiny85. This pin can be used as a PWM output,
and is also used for I2C data, and SPI data input.
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