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:
Wake-on-Shake Hookup Guide
A basic hookup guide for getting started with the SparkFun Wake-on-Shake. The board gives you the ability to put your project into hibernation until bumped or shaken awake using the ADXL362 accelerometer. This means you can design projects meant to stay inert for long periods of time, possibly even several years, depending on the battery type used to power the project.
Qwiic Keypad Hookup Guide
If you are tired of taking up GPIO pins, wiring a bunch of pull up resistors, and using firmware that scans the keys taking up valuable processing time... check out the new Qwiic Keypad.
Atto84 Hookup Guide
A bare minimum Arduino compatible breakout using a ATtiny84 for integration into your small projects!
SparkFun Qwiic Dual Solid State Relay Hookup Guide
A Hookup Guide to get you started with the SparkFun Qwiic Dual Solid State Relay.