scout_2_prototype

This is a prototype around a PCB I sent off to fab in March 2022... that I'm slowly bringing back to life. I'm kind of using it as a springboard for the next thing, whatever that is and whenever it happens!

Very much work-in-progress. License will be MIT like other kits.

Forked from scout's 2-25_keys branch

In this repo

• Kicad project
• OpenSCAD for scaffolding and keys models
• STLs for 3D-printing

Goals

Overarching Oskitone design goals

• Easy to solder. Only through-hole parts, even if it limits functionality.
• Easy to change. Code can be edited with free software and cheap hardware.
• Easy to play. No hidden menus, secret key combos, or overloading. One control per one function.
• Easy to understand. Code should be relatively accessible to anybody familiar with Arduino.
• Easy to hack. Programming header (TODO? hmm), usual open source ethos stuff.

And specific to the next ~synth

• Polyphony
  • Per my ability, four is a reasonable number of notes to play simultaneously. Three is okay but would be frustrating. Two would be funny?
  • Anyway, four notes is what D9-12 are attempting. At the time, I was thinking I could tack some math around millis() and make the square waves manually... maybe use an interrupt timer? My pin choice seems random, and there're probably better choices.
• Any kind of musical connectivity
  • MIDI
    • USB is modern but circular DIN connectors are standard and inarguably answer the question "But can it do MIDI?!"
    • I think I'd also need non-DIP chips to do USB MIDI so that's out
    • I don't know if both IN and OUT are necessary or which to prefer if there can only be one. DIN connectors are big; TRS MIDI is an option.
  • Control Voltage
    • I'm open to this but don't really know the scene well enough to know what would be good. If it's easy to add, sure.
• Support for Mozzi w/o shipping w/ it
  • I want it to still feel solidly like an Oskitone instrument, for better and no doubt worse. Blame "not invented here" syndrome.
  • Mozzi is cool as hell but it does require reading docs, which maybe breaks the "easy to understand" goal.
  • Plus, even if I wanted to, I don't think Mozzi's license would permit me selling kits w/ it. Looks like they're GNU LGPL now, so may be okay.
  • That having been said, I want to engender "side-loading" things like this and make swapping to Mozzi straightforward, especially if the barrier to entry is low. So minimally it needs the right pins, an output filter, maybe other changes too.
• More musically useful than the Scout
  • Same size keys but as many as I can fit on a Prusa.
  • A semblance of control with analog input pots. Currently doing octave and glide.
  • Glide is fun but will be weird if/when polyphony is introduced. Could do poly only at 0 glide

TODO / known issues / things for next rev

• 3D prints
  • Octave control really needs detents or some kinda tactile feedback on rotation.
• For next rev
  • Needs decoupling cap before amp, probably
  • Self-document pin connection assignments in schematic
  • Move text beyond key area
  • More key mounting screw holes? Key bed subassembly with multiple parts
  • Reverse power switch direction. It should power on when actuator is "up" like Scout
  • Note UART hookup orientation on silkscreen
  • Rethink headphone output in signal path to minimize amplified noise
• Tiny speaker is quick to distort and has no low end
• Make it clear/explicit how FUNCTION_INDICATOR_LED is used as "hanging" indicator. Right now, it's incidental.

Anything else?

final-assembly-timelapse.mp4

Uploading new code

The UART header works the same as the OG Scout.

The cable's black wire should be on the left and green on the right.

BOM

Designator	Footprint	Quantity	Designation
SW1-SW25	SW_PUSH_6mm	25	SPST
BT1	PinHeader_1x02_P2.54mm_Vertical	1	4.5v
LS1	PinHeader_1x02_P2.54mm_Vertical	1	Speaker
RV1	Potentiometer_Bourns_PTV09A-1_Single_Vertical	1	10k Log
Y1	Resonator-3Pin_W7.0mm_H2.5mm	1	16.00MHz
U2	DIP-8_W7.62mm	1	LM386
R4,R5,R7,R6	R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal	4	10K
J1	AUDIO-JACK	1	AudioJack2_SwitchT
C2,C4,C5	C_Disc_D5.0mm_W2.5mm_P5.00mm	3	.1uF
C6,C1	CP_Radial_D8.0mm_P3.50mm	2	220uF
U1	DIP-28_W7.62mm	1	ATmega328P-PU
D1-D25,D27	D_DO-41_SOD81_P10.16mm_Horizontal	26	D
J2	PinHeader_1x06_P2.54mm_Horizontal	1	Conn_01x06_Male
R8	R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal	1	1m
R9,R13	R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal	2	10k
R10,R1,R11,R3,R2,R12	R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal	6	220
D26	LED_D5.0mm-4_RGB_Staggered_Pins	1	LED_CRGB
J4,J3	DIN5-RA-PTH	2	DIN5
SW26	SW_Slide_1P2T_CK_OS102011MS2Q	1	SW_SPST
RV2,RV3	Potentiometer_Bourns_PTV09A-1_Single_Vertical	2	10k
C3	CP_Radial_D5.0mm_P2.00mm	1	1uF
U3	DIP-8_W7.62mm	1	6N138

Schematics

3D Models

Normally I'd put them on thingiverse/etc, but here they're included in the repo in the stls folder.

OpenSCAD dependencies

Assumes parts_cafe is in a sibling directory and is up to date on the main branch. Here's how I've got it:

\ oskitone
    \ parts_cafe
    \ scout_2_prototype

You'll also need to install the Orbitron font.