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ATtiny817 Breakout with seesaw - STEMMA QT / Qwiic

SKU 4186
Save 27%
Original Price £6.99 inc VAT
Current Price £5.09 inc VAT
£4.24 ex VAT
2 in stock.

This board was originally designed for use in Adafruits own projects, it is a mini-dev board that allowed them to design with the ATtiny817. However, as they are now adapting their SAMD09 designs to the ATTiny8xx series they needed a quick and easy board to test code on!

Each breakout comes with the assembled and tested board, as well as some header strips. Each PCB is fairly minimal and contains:

  • ATtiny817 8-bit microcontroller
    • 8KB flash, 512 bytes of RAM, 128 bytes of EEPROM
    • The internal oscillator can run up to 20MHz
    • Internal hardware multiplier
    • Can run from 2V to 5V power/logic (check the datasheet for max speed at desired power)
  • 3.3V regulator - by default they run at the Vin voltage, which can be 5V, but there's a solder jumper on the bottom if you'd like to select 3V logic.
  • Green power LED
  • Red indicator LED
  • Two STEMMA QT I2C connectors with 10K pullup resistors, connected to pins 10 and 11

This board comes pre-programmed with seesaw peripheral code that will let it act as an "I2C to something" converter, basically, a little I2C-controlled friend to do all the timing-sensitive things many microcontrollers and microcomputers are not good at, of course, however, you can configure or reprogram the chip to however you want to use it

Please Note: The boards do not come with a bootloader. If you want to do development on seesaw (e.g. changing the configuration) you need a separate UPDI programming setup! The firmware put on is available as an example sketch, compiled using the megaTinyCore.

Examples of using this breakout with the pre-burned seesaw firmware:

  • 14 x GPIO with selectable pullup resistors
  • 9 x 10-bit ADC inputs - pins 0, 1, 2, 3, 6, 7, 18, 19, 20
  • 5 x 8-bit PWM outputs - pins 0, 1, 9, 12, 13
  • 1 x NeoPixel output (up to 60 pixels)
  • 1 x EEPROM with 127 bytes of NVM memory (handy for storing small access tokens or MAC addresses) - last byte of EEPROM is used for I2C address selection
  • 1 x Interrupt output that can be triggered by any of the accessories - pin 15
  • 2 x I2C address selection pins - pins 16 and 17
  • 1 x Activity LED on pin 5, tied active low


  • Dimensions: 33.0mm x 12.8mm x 4.6mm / 1.3" x 0.5" x 0.2"
  • Weight: 1.1g / 0.0oz