How to Install an ATtiny Bootloader With Virtual USB
Contributors:
Shawn Hymel
Shawn Hymel 
Resources and Going Further
While this is a lot of information to take in, it shows how to hack the Arduino IDE to load custom board definitions. These steps should work for other ATtiny devices that are supported by the micronucleus project, such as:
You might have to modify the pins_arduino.h file, however, if you plan to use a different ATtiny.
ATtiny84 Pinout
If you need additional support, please check out the following resources.
If you want to go further with the ATtiny, please check out our additional tutorials that showcase the ATtiny:
Pi AVR Programmer HAT Hookup Guide
In this tutorial, we will use a Raspberry Pi 3 and the Pi AVR Programmer HAT to program an ATMega328P target. We are going to first program the Arduino bootloader over SPI, and then upload an Arduino sketch over a USB serial COM port.
Qwiic Single Relay Hookup Guide
Get started switching those higher power loads around with the Qwiic Single Relay.
Qwiic MP3 Trigger Hookup Guide
Playing MP3s has never been easier.
Thing Plus Dual-Port Logging Shield Hookup Guide
This tutorial shows you how to hook up and use the SparkFun Thing Plus Dual-Port Logging Shield.