Author: tbess

• Measurements for guitar collected
• PCB parameters decided
• PCB layout finalized
• Planning to place order on Monday 10/19

MIDI Guitar Hardware Update

Donor guitar

• Fender Squier Telecaster (25.5″ scale, 21 frets)
• Chosen for its bolt-on neck, roomy control cavity, and low cost
• An initial check showed 18″ from the nut to fret 21, which matches the theoretical 25.5″ scale layout

Fret sensing plan

• A custom flex PCB overlay sits on the frets, with 126 pads (6 strings × 21 frets)
• Each pad has its own trace, and the grounded string pulls a pad low when pressed
• This lets us detect chords with several strings on the same fret

Measurements we’re collecting for the PCB layout

• Nut-to-fret-crown distances, checked against the calculated fret positions
• Fret crown width, height, and length
• Fretboard width at the nut, fret 12, and fret 21, plus the fretboard radius
• Each string’s lateral position at frets 1, 12, and 21, plus at the nut and saddle
• String gauges and nut-to-saddle distance
• Baseline string action, to plan for the overlay thickness

Pluck and velocity sensing: Roland GK-3

• We selected the Roland GK-3 divided (hexaphonic) pickup, which gives a separate signal for each string
• It mounts without drilling, so the stock bridge stays in place and each string’s ground path is preserved
• It also makes the setup reversible, which suits prototyping
• Our own ADC and firmware will read the six signals for pluck timing and velocity
• Still to confirm: breakout box and cable, mounting position on the Tele, and ADC front end

Next steps

• Finish the measurements and generate the pad layout
• Order a test flex PCB, and prototype the scanning firmware on a bench board first

Found suitable donor guitar on Facebook Marketplace. Negotiating and planning to purchase this week.

Finalized overall design for the guitar’s fret matrix. Planning to implement in KiCad and order flex PCB after the precise measurements are taken of our guitar neck.

 

Researched the MIDI protocol.

Weighed the trade-offs of using a donor guitar versus building our own.

Looked at donor guitar options.

Learned about piezo hex bridge and its installation on an existing guitar.

Research .wav format as an alternate to MIDI evaluating pros and cons of both file formats.