ATTINY817-XMINI Microchip, Evaluationskit, ATtiny817/816/814/417-MCUs, Xplained Mini | Farnell DE
ATTINY814 Datasheet(PDF) - Microchip Technology
A simple and inexpensive way to program new AVR ATtiny214, ATtiny414, ATtiny814 and Atmega microcontrollers using by the UPDI interface - ООО "НПК "Спецтехнаука"