The Guitarduino tuner does what any guitar tuner should do: tells you if your guitar is in tune or not. The guitar is plugged into the tuner through a 1/4 inch audio jack, and the tuner is turned on by a power switch on the side. The display screen then turns on, with the words “Play a note!”. Once a note is played and a frequency is detected, the display screen shows what note is being played and whether it is flat (b), sharp (#), or in tune.
The Guitarduino Tuner uses a TL-082 Op-Amp to amplify and send the frequency signals to the Arduino. Once the Arduino receives the signal, it converts the signal to a frequency value using an FFT algorithm, and then uses the value of the most dominant frequency to determine what note is being played.
Here is a video of the signal the op-amp is sending the Arduino shown by an oscilloscope: https://youtu.be/61w8PFVtrfY