“This article describes a simple function generator based on an ATtiny85 which allows you to generate a virtually unlimited number of waveforms using additive harmonic synthesis, by specifying the amplitude of each of the waveform’s harmonics:
It includes a volume control, audio amplifier, and loudspeaker so you can hear the waveforms. It’s not only a useful waveform generator, but also a good introduction to the composition of musical notes.
Introduction
Unlike most of my other projects on Technoblogy I didn’t originally set out to design this. I got the idea after working out a way to add a sine wave to my original Tiny Function Generator project, realising I could take this one step further and use the same technique to allow you to generate arbitrary waveforms by specifying the amplitude of each of their harmonics.
Because I wanted to hear the effect on a waveform of modifying individual harmonics, I also added an audio amplifier and volume control to the design so it will drive a loudspeaker.”