PipKey v2 MIDI Instrument

The 2nd iteration on a concept for a handheld MIDI instrument. It uses a Nunchuck and/or a magnetic rail to shift notes.

Information:
• Everything was printed at a layer height of 0.2mm.
• In the right orientation, only the “Main” bodies require supports.
• The version of the assembled parts shown in the images differs slightly from the uploaded files. A few minor adjustments were made during the testing process and I was too lazy to reprint everything again.
• Once covered in copper tape, the patterns on the bottom of the rail connect various pins on the battery connecter to the grounded center pin. With the magnets on the slide/rail snapping into place at discrete points, you can measure distance like the frets on a guitar.
• Print the tiny indents on the rail with a different color in your slicing software to make placing the copper tape easier. I originally tried using conductive PLA for these rail pads again (as seen in PipKey v1), but the pressure required to make solid contact with the conductive PLA works against making the slide/rail move smoothly.
• The “Arm” Mount actually works better if you just operate it with your right hand.
• All the buttons/battery connector inputs use the INPUT_PULLUP pin mode.
• The nunchuck must be wired to I2C Wire0 while the display must be wired to a different Wire pin (i.e. Wire1). This is reflected in the code. This is also where the Teensy comes in handy.
• Pardon the rambling factoids. More info/a guide is available upon request.

Controls Explanation:
• There are four modes: Major/Minor (operates off half/whole steps), Pentatonic (operates in sets of 5 notes), and String (operates entirely in half steps). Each mode creates a “scale” that is traversed numerically through the main buttons and nunchuck/rail.
• The on/off switch near the thumb button puts the device in menu mode. Here you can use buttons 2 and 3 to move up and down the base note for the scale, as well as change the scale mode using button 1 (the thumb button).
• Moving the rail up moves the notes up one note. It's more like shifting positions on a string instrument. The rail is primarily designed for use with String Mode.
• On the Nunchuck:
• C-button: shift back two notes
• Z-button: shift forward two notes
• Up/Down: Octave Up/Down (8 notes for scales, 5 notes for pentatonic, 12 for string)
• Left/Right: MIDI note velocity up/down
Materials:
• PLA/PETG
• Solid core wire
• Flat breadboard jumper wires
• ½-size Breadboard
• Teensy 4.0
• Various M2/M3 screws and nuts
• 5-pin Spring battery connector (same as PipKey v1)
• 5x Kalih Choc keyboard keys
• Copper tape
• Many 5x2mm Magnets
• Small switch (SS12F15-G5)
• Digispark (I think) I2C OLED (128x64)
• 40mm Stretch fabric (cut in half for Main Body strap)
• Magnetic clasps
• Wii Nunchuck
• Adafruit Nunchuck Adapter
• 2x 8x4mm bearings
• Android Phone with Fluidsynth
• Female-to-Female jumper cables (for OLED to breadboard)
• Longer Male-to-Male Headers (for OLED to breadboard)

Room for Improvement:
• Feature creep is dangerous.
• I initially tried to conceptualize combining the rail and nunchuck (you could move the rail while also holding the nunchuck on some mount that would go on the rail) but ultimately found it easier to operate just one at a time. They each have their strengths and weaknesses, something I hope to remedy in the future.
Direct magnet-to-magnetic contact made for some really promising slide/rail mechanisms during testing (one image of this has been uploaded), but the spring battery connector introduces a lot of friction, even with the two bearings on the opposite side of it.
• Pressing buttons is easier/faster than moving a plastic slide around. Pressing buttons is also easier/faster than using a joystick. This conclusion makes me want to create a 5x5 button version that ditches both the slide/rail AND the nunchuck in favor of using only buttons for both the left and right hand. This would probably end up looking like a concertina or something.