Here are a bunch of Oryng Wiring Framework (aka Arduino) Libraries that I’ve either created or modified over the years.
The libraries are mirrored on GitHub and BitBucket.
Produces square wave tones on arbitrary pins.
Produces PWM signals on arbitrary pins.
A timer library for working with millis(), providing for an easy way to have a recurring action.
Rogue Robotics MP3 module library.
Rogue Robotics SD module library.
Originally written by Alexander Brevig, I updated (some would say I “bloated” it) the library to have a bunch of more functionality.
Variable color depth version of the LPD8806 library.