The next 2 pins are also used for USB programming. This pin can be used as an analog input (known as Analog A1), and is also used for I2C clock and SPI clock. GPIO #2 - this is connected to PB2 on the ATtiny85.This pin is also connected to the onboard LED (like pin 13 on a regular Arduino). This pin can be used as a PWM output, and is also used for SPI data output. GPIO #1 - this is connected to PB1 on the ATtiny85.This pin can be used as a PWM output, and is also used for I2C data, and SPI data input. GPIO #0 - this is connected to PB0 on the ATtiny85.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

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! On a 3V Trinket, the GPIO are 3.3V output level, and should not be used with 5V inputs. 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

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 pinĪll the GPIO pins can be used as digital inputs, digital outputs, for LEDs, buttons and switches etc.

Underclock adafruit trinket 5v