Generate Harmonics with an ATtiny85 on a Beautifully Laid Out Breadboard

The ATtiny85, as its name implies, is indeed tiny, with a limited number of IO pins and a very low cost. Hacker David Johnson-Davies decided to make a harmonic function generator powered by it, along with a small Texas Instruments LM4817 amplifier and a speaker for audio output. The whole circuit, including a tiny 128x32 OLED display and user inputs, is extremely well laid out, and fits on a small breadboard.

The idea for this came after considering how to add a sine wave to his Tiny Function Generator project. After some consideration he realized that he could produce other waveforms by specifying the amplitude of the original waveform’s harmonics. These harmonics — multiples of the wavelength of the original signal’s frequency/sound — are specified using buttons and encoder on the circuit down to the 10th harmonic level.

A simple sine wave is generated when each harmonic except for the first is set to zero, and from there all kinds of other waveforms can be generated, like a sawtooth or an approximation of a square wave. Interestingly, you can also turn off the fundamental frequency with the appropriate harmonics enabled in order to allow you to hear that missing frequency. The project looks great for those who want to get started with electronic music and function generation, and you can find ATtiny85 code for it here.