seedbox/docs/hardware/wiring.md

Wiring

One stripboard carries the Pico and the MIDI circuits. Everything on the panel (screen, encoder, pots, buttons, jacks) connects to it with hookup wire.

Board positions are strip letter + hole number. For example V4 is strip V, hole 4, counted from the left with the parts facing you. Strips run left to right: A at the top (the USB edge), then Z, AA, AB at the bottom.

The interactive version, with the same drawings, is tools/wiring.html. Generated from hardware/layout.js.

Wire map: panel to board

Every panel wire and the board hole it lands in: strip letter, then hole number counted from the opto end.

Part	Lug	Wire	Board hole
Buttons	Row 1 · KICK, KICK 2, SNARE	yellow	D2
	Row 2 · HAT, HAT 16, PERC, GHOST	yellow	E2
	Row 3 · BASS, MEL A, MEL B, PAD	yellow	G2
	Col 1 · KICK, HAT, BASS (diode band side)	green	I2
	Col 2 · KICK 2, HAT 16, MEL A	green	J2
	Col 3 · SNARE, PERC, MEL B	green	K2
	Col 4 · GHOST, PAD	green	L2
SEED	one lug	yellow	Q2
RUN toggle	middle lug (it sits in the button grid, row 1 / col 4)	yellow	S2
SEED + RUN	ground: SEED other lug, RUN one outer lug	black	AA6
Encoder	VCC (3.3 V, never 5 V)	red	AB4
	GND	black	AA4
	SW	green	P2
	SIB	green	O2
	SIA	green	N2
ENERGY pot	middle lug	blue	J27
DRIFT pot	middle lug	blue	I27
Pots	right lugs, both (3.3 V)	red	AB25
	left lugs, both (AGND)	black	H27
LCD	1 · VCC (3.3 V)	red	AB23
	2 · GND	black	AA23
	3 · SCE	blue	S27
	4 · RST	blue	N27
	5 · D/C	blue	O27
	6 · DN (MOSI)	blue	P27
	7 · SCLK	blue	Q27
	8 · LED, through a 330 Ω resistor (if dark, move to any AA hole)	red	AB22
MIDI IN jack	tip	blue	W1
	ring	blue	Y1
OUT KIT jack	tip	blue	X26
	ring	red	V22
	sleeve	black	AA22
OUT SYNTH jack	tip	blue	U31
	ring	red	V31
	sleeve	black	AA31

Wire colours

Colour	Role
Red	3.3 V and the MIDI OUT ring lugs
Black	ground
Yellow	button rows, SEED, RUN
Green	button columns, encoder
Blue	screen, pots, MIDI signals
Grey	short links on the board

If your spools are other colours, keep the roles and rename them. Red and black for power and ground matter most.

Board · parts side

• Size: 34 holes × 28 strips, about 86 × 71 mm.
• Pico: sits in two 20-pin female headers with pins 1 and 40 on strip A. Its USB end is flush with the top edge of the board, and the micro-USB socket reaches just past it.
• Mounting: lay the board on the box floor with that edge against the back wall, behind the USB slot. The socket is about 41 mm from the board's left edge.
• Pads: the numbered dots P1 … P35 are where off-board wires solder.

Board · copper side, for cutting

This view is flipped: hole 1 is on the right.

How to cut:

• Use a 3–4 mm drill bit turned by hand, or a spot-face cutter.

• Check each cut with the meter's continuity beeper.

• Hole 6 on strips U to Y (5 cuts)

• Hole 14 on strips U to X (4 cuts)

• Hole 16 on strips A to T (20 cuts)

• Hole 23 on strip X (1 cut)

• Hole 25 on strips U to W (3 cuts)

Power strips along the bottom

• Z: 5 V from the Pico's VBUS. Only the opto uses it.
• AA: ground.
• AB: 3.3 V from the Pico's 3V3 pin.

Every red wire to the panel starts on AB. Every black wire starts on AA, except the pots, which use the AGND strip.

Board parts and links

Part	Value	Holes	Note
Pico 2W	2 × 20-pin female header	A13–T13 and A20–T20 (pins 1–20 down the left, 40–21 down the right)	USB end flush with the top edge of the board, past strip A
U1	6N137	U5–X5, U8–X8	6N137 in a DIP-8 socket. Notch toward strip U, pin 1 at hole U5. Pin 7 (enable) is tied to pin 8 by the U10–V10 link.
R1	220 Ω	V2 – Y2	MIDI IN current limit. 3-hole span: stand it upright, or use a small ⅛ W part flat. If learning ever misses notes, use 150 Ω.
D1	1N4148	V4 – W4	Band (cathode) on V4, the opto LED anode side. Stands upright (1-hole span).
R2	1 kΩ	W10 – AB10	Opto output pull-up to 3.3 V
C1	100 nF	U11 – X11	6N137 supply bypass, right beside the chip: U11 is its 5 V (pin 8) strip, X11 its GND (pin 5) strip. Required. Fit it after the beep test.
R4	10 Ω	X21 – X25	MIDI OUT KIT, TX line (RC). Lies flat along strip X, across the cut at X23 (4-hole span, ¼ W fits). SEED hangs right above it.
R5	33 Ω ½ W	V19 – AB19	MIDI OUT KIT, 3.3 V line (RA). ½ W: a mono plug in the jack shorts it to ground.
R6	10 Ω	U28 – Y28	MIDI OUT SYNTH, TX line (RC)
R7	33 Ω ½ W	V30 – AB30	MIDI OUT SYNTH, 3.3 V line (RA). ½ W, same reason as R5.
Link	wire	A34 – Z34	5 V (VBUS) to the 5 V strip
Link	wire	E32 – AB32	3V3 to the 3V3 strip
Link	wire	R33 – AA33	GND to the GND strip
Link	wire	U13 – Z13	opto VCC to 5 V
Link	wire	U10 – V10	opto enable (pin 7) to VCC (pin 8): the 6N137 output only works with pin 7 high
Link	wire	X12 – AA12	opto GND to GND
Link	wire	W9 – B9	opto out to GP1 (MIDI RX), strip B
Link	wire	A15 – X15	GP0 (TX KIT) to strip X (R4), straight down under the Pico between its headers
Link	wire	F14 – Y14	GP4 (TX SYNTH) to strip Y (R6), straight down under the Pico between its headers

Off-board wires

Pad	Board hole	Colour	Pico pin / signal	Goes to
P1	Y1	blue	via R1 to opto	MIDI IN jack · ring (pin 4)
P2	W1	blue	opto cathode	MIDI IN jack · tip (pin 5)
P3	X26	blue	via R4 (10 Ω) from GP0	OUT KIT jack · tip (pin 5)
P4	V22	red	via R5 (33 Ω) from 3V3	OUT KIT jack · ring (pin 4)
P5	AA22	black	GND strip	OUT KIT jack · sleeve (pin 2)
P6	U31	blue	via R6 (10 Ω) from GP4	OUT SYNTH jack · tip (pin 5)
P7	V31	red	via R7 (33 Ω) from 3V3	OUT SYNTH jack · ring (pin 4)
P8	AA31	black	GND strip	OUT SYNTH jack · sleeve (pin 2)
P9	N27	blue	GP21	LCD · RST (pin 4)
P10	S27	blue	GP17	LCD · SCE (pin 3)
P11	O27	blue	GP20	LCD · D/C (pin 5)
P12	P27	blue	GP19	LCD · DN/MOSI (pin 6)
P13	Q27	blue	GP18	LCD · SCLK (pin 7)
P14	AB23	red	3V3 strip	LCD · VCC (pin 1)
P15	AA23	black	GND strip	LCD · GND (pin 2)
P16	AB22	red	3V3 strip	LCD · LED (pin 8) through 330 Ω
P17	N2	green	GP10	Encoder · SIA
P18	O2	green	GP11	Encoder · SIB
P19	P2	green	GP12	Encoder · SW
P20	AB4	red	3V3 strip	Encoder · VCC
P21	AA4	black	GND strip	Encoder · GND
P22	J27	blue	GP26	ENERGY pot · middle lug
P23	I27	blue	GP27	DRIFT pot · middle lug
P24	AB25	red	3V3 strip	Pots · right lugs (chain both)
P25	H27	black	AGND	Pots · left lugs (chain both)
P26	Q2	yellow	GP13	SEED · one lug
P27	S2	yellow	GP14	RUN toggle · middle lug
P28	AA6	black	GND strip	Panel ground bus · SEED other lug, RUN one outer lug
P29	D2	yellow	GP2	Matrix row 1 (KICK, KICK 2, SNARE)
P30	E2	yellow	GP3	Matrix row 2 (HAT, HAT 16, PERC, GHOST)
P31	G2	yellow	GP5	Matrix row 3 (BASS, MEL A, MEL B, PAD)
P32	I2	green	GP6	Matrix column 1 (KICK, HAT, BASS)
P33	J2	green	GP7	Matrix column 2 (KICK 2, HAT 16, MEL A)
P34	K2	green	GP8	Matrix column 3 (SNARE, PERC, MEL B)
P35	L2	green	GP9	Matrix column 4 (GHOST, PAD)

Panel wiring

Button matrix, seen from the back

Each button:

• One lug goes to its row wire (yellow), daisy-chained along the row.
• The other lug goes through a diode to its column wire (green), daisy-chained down the column.
• The diode's band points to the column. Solder the diodes straight onto the button lugs and sleeve them. 1N4148, 1N4448 or any small-signal diode works.

11 track buttons, each with its own diode, plus D1 on the board: 12 diodes. GHOST is wired at row 2 / column 4. The RUN toggle sits in the grid's row 1 / column 4 spot but isn't part of the matrix, so row 1's wire stops at SNARE and column 4 starts at GHOST.

Drawn from behind the panel, the side you solder on: KICK is top-right, RUN top-left.

MIDI jacks: 3.5 mm TRS, Type A

Jack	Tip (pin 5)	Ring (pin 4)	Sleeve (pin 2)
MIDI IN	P2	P1	stays empty
OUT KIT	P3	P4	P5
OUT SYNTH	P6	P7	P8

• Jack type: use stereo (TRS) jacks; mono ones have no ring.
• Lug order: it differs between jack models. Find the tip, ring and sleeve lugs with the meter and a plug inserted.
• Cables: Type A is the MIDI standard, so a plain stereo 3.5 mm cable goes straight to another Type A device (e.g. SP-404MKII). A DIN device (e.g. MiniFreak) needs a TRS-to-DIN adapter that says Type A. A Type B one swaps tip and ring and gives silence; nothing breaks.

Nokia 5110 module

• Pin order as printed on your module: 1 VCC, 2 GND, 3 SCE, 4 RST, 5 D/C, 6 DN (MOSI), 7 SCLK, 8 LED.
• LED (backlight): wire it through a 330 Ω resistor to AB22 (3.3 V), with the resistor inline at the module end, sleeved. If it stays dark, move that wire to any free hole on strip AA (ground). GP22 (L27) stays free; it's only needed for dimming later, through a transistor.
• SCE can go straight to ground instead of S27 if it's the only thing on the SPI bus. That frees GP17.

Encoder module

Pin order as printed on your module: VCC, GND, SW, SIB, SIA. Power it from 3.3 V (AB4), never 5 V: its pull-up resistors would put 5 V on the Pico's pins. If clockwise steps the wrong way, swap SIA and SIB (or flip it in firmware).

Pots, SEED, RUN

• Pots, lugs facing down, shaft toward you:
  • left lug to AGND (P25)
  • middle lug to its pin
  • right lug to 3.3 V (P24)
  • Chain the left lugs together and the right lugs together.
  • If the readings jitter, solder a 100 nF capacitor at each pot, from wiper to left lug.
• SEED: one lug to P26, the other to the ground bus (P28).
• RUN: middle lug to P27, one outer lug to the ground bus. If RUN and STOP come out swapped, use the other outer lug.

Build order and checks

Board

1. Cut the board to 34 × 28 holes. For the top edge, cut through the row of holes above strip A, then sand it back to about 1.3 mm from the strip A holes, stopping before the strip A copper. That puts the Pico's edge flush with the board. Unsanded, the Pico sits about 1 mm back, which still works if the wall slot lets the plug's moulding through. Make the track cuts and beep each one out.
2. Solder the two Pico headers and the DIP-8 socket (notch toward strip U). Then the resistors and the diode (band on V4).
   • Keep everything low, because the SEED button hangs right above R4. R4 lies flat along strip X, across the cut at X23.
   • R1's 3-hole span is tight for a ¼ W body, so stand R1 upright or use a small ⅛ W part.
   • Leave C1 for step 4.
3. Solder the grey links with insulated wire. The two long ones (GP0 and GP4) run straight down under the Pico, between its two headers, so fit them before the Pico goes in.
4. Before fitting C1, with the Pico and the 6N137 out, check that AB to AA does not beep and Z to AA does not beep. Then fit C1. It can chirp briefly on the beeper once it's in.

First power

1. Plug in the Pico only and power it from USB. Measure AB to AA: about 3.3 V. Z to AA: about 5 V.
2. Unplug, then insert the 6N137 (notch toward strip U, pin 1 at hole U5).
3. Wire the panel. Before closing the box, check that no bare lugs touch each other.
4. Flash the firmware. Set GP0 and GP4 to 8–12 mA drive (see pinout).