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:
Soft Circuits: LED Feelings Pizza
Here we will learn how to say how you feel with pizza. Electric pizza.
Pocket AVR Programmer Hookup Guide
Skip the bootloader and load your program directly onto an AVR with the AVR Pocket Programmer.
Qwiic Twist Hookup Guide
Take your volume knob beyond 11 with the Qwiic Twist digital RGB LED encoder via I2C!
SparkFun Qwiic Dual Solid State Relay Hookup Guide
A Hookup Guide to get you started with the SparkFun Qwiic Dual Solid State Relay.