Guitar To MIDI Using The LogoChip V2

A guitar to MIDI interface was designed that was intended to serve as an interface between guitar playing and MIDI control of external hardware and software. This document describes the details of the design, experimentation, implementation and final outcome of the project. The original plan was not nearly completed in the time expected, as many important issues
Guitar To MIDI Using The LogoChip V2 - schematic

that were not apparent before arose along the way. This issues are presented in this document and can serve as a valuable source of information for the design of a similar project, or one involving any of the key aspects of this project, namely interfacing a physical musical instrument with software using a PIC. The initial design for this project called for an optical pickup for each string that fed the audio signal from that string alone to the input of of an analog switch, which controlled the current string being fed to an Analog-to-Digial input of the LogoChip V1 input. The LogoChip was to step through each input as needed, and sample a duration of the signal, providing a sample window of each string that could be used to gather pitch, volume, and other attributes of the sound. Inside the LogoChip, the sample would be analyzed for the time between zero crossings in the waveform, providing a wavelength of the signal, which could be used to determine pitch. The amplitude of this waveform over time would provide realtime changes in volume. The data gathered from the input sampling was to be sent as MIDI information for note on and off events, with initial note volume (velocity) as set by the initial volume of the waveform, realtime volume change sent based upon volume change of the input signal, and pitchbending to follow that of the guitar, all of which being sent on a different channel for each string. The different...

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