At the heart of the device is a AD9833 waveform generator; with the Arduino, rotary encoder, and 16×2 LCD providing an interface to control it over SPI. Unfortunately, the AD9833 doesn’t have ...

I needed a rotary encoder — I pulled a cheap one out of one of those “49 boards for Arduino” kits you see around. Not the finest encoder in the land, I’m sure, but it should do the job.