A simple and inexpensive way to program new AVR ATtiny214, ATtiny414, ATtiny814 and Atmega microcontrollers using by the UPDI interface - ООО "НПК "Спецтехнаука"
Atmel (Microchip) tinyAVR 1-Series - Jay Carlson
AVR42781: Getting Started With ATtiny417/814/816/817