The Puitar features a keypad matrix of 22 frets and six strings. When the player presses a string on a fret, they are connected, which means electricity can flow between them. This is detected on one of the Raspberry Pi’s GPIO pins and the appropriate note is played. “To find out which frets are pressed, we loop over the strings, setting [them] high, one at a time and checking which fret turns to show high,” explains Behruz. “The rest is a simple software project to make sounds for the pressed frets.”
To create the matrix, he drilled holes in the fretboard and soldered wires to the frets from below. After building the first prototype, however, he found that he frets would sometimes link the strings and make the guitar malfunction. “The solution is very simple: cut each fret in six parts that are separated, and connect them by diodes instead so they will conduct the electricity only in one direction, and separate the strings, although doing that manually with real fret wire will take ages.”
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