Multi-Instrument Note Tuner

A note tuner on a custom ESP32 PCB that hears a note, tells you how far off you are, and plays the reference tone back.

The board pulls a MEMS microphone, an audio amplifier, a speaker, and an OLED display onto a single ESP32-based design. Incoming audio runs through an FFT to pick out the fundamental across a 25 Hz–4.5 kHz range — low enough for the bottom of a piano, high enough that harmonics stay unambiguous — and the OLED redraws at 60 Hz with the nearest note, the pitch error, and which way to bend. Three buttons switch between piano, guitar, and ukulele presets, and the amplifier and speaker let the board sound the reference tone rather than only measuring against it.

The schematic and PCB layout were drawn in ECAD, which is where most of the work actually was: the microphone is an analog part sitting on the same board as a switching-heavy display and a speaker driver, so the layout has to keep that signal clean before any of the FFT math matters.