The default I2C address is 0x49.

Power Pins:

• Vin - this is the power pin. The ATtinyx16 operates between 1.8V and 5.5V. However, we still included a 3.3V voltage regulator. You can power the board from 2V to 5V. It defaults to Vin voltage, which can be between 3.3V and 5V, or cut the jumper on the back and bridge the other pad to select 3.3V logic.
• 3V - This is the 3.3V output from the voltage regulator. You can grab up to 100mA from this if you like.
• G - This is common ground for power and logic.

I2C

• SCL - This is the I2C clock pin. Connect to your microcontrollers I2C clock line. There is a 10K pullup on this pin to Vin.
• SDA - This is the I2C data pin. Connect to your microcontrollers I2C data line. There is a 10K pullup on this pin to Vin.
• STEMMA QT - These I2C connectors, located on each end of the board, have 10K pullup resistors. They allow you to connect to development boards with STEMMA QT connectors, or to other things, with various associated accessories.

seesaw GPIO Pins:

• 0-5, 11, 14, 15, 16 - These are the 10 GPIO pins available with selectable pullup resistors.

seesaw Interrupt Pins:

• 6 - This pin can be set to pull low by the breakout and can signal to your host microcontroller that an interrupt has occurred.

seesaw I2C Address Pins:

The default I2C address is 0x49.

• 12 / AD0 - This is the ADDR0 pin. Connect this to ground to increment the device's I2C address by 1.
• 13 / AD1 - this is the ADDR1 pin. Connect this to ground to increment the device's I2C address by 2.

seesaw NeoPixel-Capable Pins:

• 0-5, 11, 14, 15, 16 - Any GPIO pin can be a NeoPixel pin, however, you can only use one pin at a time. There is only one NeoPixel buffer, and therefore only one NeoPixel output. It can drive up to 60 pixels.

ADC Pins:

• 0-5, 14, 15, 16 - There are nine 10-bit ADC pins.

PWM Pins:

• 0, 1, 7, 11, 16 - There are five 8-bit PWM output pins.
  

Programming Pins:

• UPDI - This is the single-pin Unified Program and Debug Interface. This pin is for external programming or on-chip-debugging. It uses the reset pin on the ATtiny.