Seedbox build sheet

Everything for the Pico 2W build: Nokia 5110 screen with the on-screen track map, 11 track buttons in a diode matrix, encoder, two pots, SEED, RUN, one MIDI in and two MIDI outs. "Have" means it was on your parts list; tick items off as you find them in the drawers.

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Pin map

GPIO	Function	Connects to
GP0	UART0 TX · MIDI OUT A	10 Ω → OUT KIT tip (pin 5)
GP1	UART0 RX · MIDI IN	6N137 pin 6 (1 kΩ pull-up to 3V3)
GP4	UART1 TX · MIDI OUT B	10 Ω → OUT SYNTH tip (pin 5)
GP2 GP3 GP5	Button matrix rows	Inputs with internal pull-ups
GP6 GP7 GP8 GP9	Button matrix columns	Driven low one at a time
GP10 GP11	Encoder A / B	Encoder module SIA / SIB
GP12	Encoder push	Encoder module SW
GP13	SEED button	Button to GND, internal pull-up
GP14	RUN toggle	Toggle to GND, internal pull-up
GP17	LCD SCE	Can be tied to GND instead (frees the pin)
GP18	SPI0 SCK	LCD SCLK
GP19	SPI0 TX	LCD DN (MOSI)
GP20	LCD DC	LCD D/C
GP21	LCD RST	LCD RST
GP22	Free	Only for backlight dimming later, through a transistor
GP26	ADC0 · Energy pot	Pot wiper (ends to 3V3 and AGND)
GP27	ADC1 · Drift pot	Pot wiper (ends to 3V3 and AGND)
GP15 GP16 GP28	Spare	GP28 is also an analog input
GP23 24 25 29	Reserved	Used by the Pico 2W's wireless chip, don't wire

Wiring notes

MIDI OUT (×2, 3.3 V spec, TRS Type A)

3V3 ──33 Ω── ring   (DIN pin 4)
TX  ──10 Ω── tip    (DIN pin 5)
GND ──────── sleeve (DIN pin 2)

Lug order differs between jack models: find tip, ring and sleeve with the meter and a plug inserted.

MIDI IN (6N137)

ring ──220 Ω── opto 2 (anode)
tip  ───────── opto 3 (cathode)
1N4148 across 2–3, band to pin 2
opto 8 → VBUS (5 V)   opto 5 → GND
opto 6 → GP1, 1 kΩ to 3V3
opto 7 ──────── opto 8 (enable high)
100 nF across 8–5 (required)

Pull the output up to 3V3, never 5 V. The sleeve stays unconnected on the input.

Button matrix (3 × 4)

        C0 GP6  C1 GP7  C2 GP8  C3 GP9
R0 GP2  KICK    KICK 2  SNARE   (RUN toggle, not in matrix)
R1 GP3  HAT     HAT 16  PERC    GHOST
R2 GP5  BASS    MEL A   MEL B   PAD

Same layout as the lid: the RUN toggle sits in row 1 / column 4, but it has its own pin (GP14), so that matrix slot is empty. Each button: row → switch → 1N4148 → column, band toward the column. The diodes let you hold several buttons at once without phantom presses.

Nokia 5110 module

VCC to 3V3, not 5 V. Logic connects straight to the Pico, no resistors.
Backlight polarity differs between red and blue boards. Test which way yours lights (BL to GND or to 3V3), then either hard-wire it or switch that side with a transistor for dimming (NPN on the ground side, PNP on the 3.3 V side).
Contrast is set in firmware and drifts a little with temperature. Expect to tune it once.

Encoder and pots

Power the encoder module from 3V3. Its onboard pull-ups would otherwise put 5 V on the Pico pins.
Pots: one end to 3V3, the other to AGND (pin 33), wiper to the ADC pin. A 100 nF cap from each wiper to AGND calms jitter.

Panel layout

See the panel layout page (landscape): screen with the encoder on the left, ENERGY / DRIFT / SEED in the middle, the 4 × 3 block on the right (11 track buttons, RUN toggle top-right).
Screen sits on the lid, wires through one hole hidden under the module. USB and the three jacks on the back wall; the Pico's USB end sits at the stripboard edge, behind the slot.

No longer needed

USB panel extension, standoffs and screws (stripboard glued behind a slot instead) · 0.91" OLED (replaced by the Nokia screen) · WS2812 LED strip (the screen shows track state) · 4.7 kΩ opto resistor (6N138 only) · 470 Ω resistors (old 5 V MIDI out values) · 5-pin DIN jacks (3.5 mm TRS instead).