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# PM_S‑1 Stage

A foot‑pedal polymeter stompbox — hands‑free footswitches, expression‑pedal tempo, a floor‑readable RGB beat light, and analog instrument pass‑through with the click mixed in.

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## What it is

HardwareFoot‑pedal stompbox~$52 one‑off

A foot‑operated polymeter stompbox for the stage: drive it hands‑free with two heavy footswitches and an expression pedal, read it off the floor from the big RGB beat light, and run your instrument through it with the click mixed in. (For a desk/lesson unit with a full screen, see the Teacher.)

The controls are built for feet: the left footswitch taps tempo (hold to start/stop), the right steps through your set list (hold for previous), and a 1/4″ expression‑pedal input sweeps tempo on the fly. Your instrument passes through (1/4″ in) with the click summed in the analog domain and sent to a balanced 1/4″ TRS out. Powered over USB‑C — with a second USB‑C "thru" port so several pedals daisy‑chain off one charger or power bank.

Dimensions & layout — ≈ 4.7 × 3.7 × 1.5 in (120 × 93 × 38 mm), a 1590BB‑style stompbox

↕ 3.7 in (93 mm)
Front
angled TFT · RGB beat light · Tap + Next footswitches
↔ 4.7 in (120 mm) wide
↕ 1.5 in (38 mm)
Top edge — I/O
Trig · Inst In · Out TRS · Exp · USB‑C · USB‑C thru
↔ 4.7 in (120 mm)
Spec & bill of materials

Rough parts list — a foot‑operated RP2040 stompbox (USB‑C, dual‑port) with analog click injection. Ballpark one‑off prices (USD); cheaper at volume.

Part | Qty | ~$
--- | --- | ---
Brain & display
RP2040 board, USB‑C — e.g. Waveshare RP2040‑Zero | 1 | 4
1.3″ IPS TFT, ST7789 — SPI; angled BPM / item readout | 1 | 6
High‑bright diffused RGB beat indicator — floor‑readable | 1 | 1
Controls
Heavy‑duty momentary footswitch (soft‑touch) — Tap · Next | 2 | 6
1/4″ expression‑pedal input jack (TRS) — tempo sweep | 1 | 1
Audio — analog click injection
PCM5102A I²S DAC — line‑level click | 1 | 3
Dual op‑amp, NE5532 / OPA2134 — hi‑Z instrument buffer + summing mixer | 1 | 1
Balanced line driver, DRV134 — → 1/4″ TRS out | 1 | 4
Connectors & power
1/4″ jack — Inst In (TS) · Out (TRS) · Trig In (TS) | 3 | 3
2× USB‑C (data+power & power‑thru) + power‑path/protection + PWR LED — daisy‑chain pedals | 1 | 3
Build
Custom PCB (or perfboard) | 1 | 5
Passives, headers, wire — R/C for the analog stage + decoupling | — | 3
Die‑cast aluminium stompbox (Hammond 1590BB‑style) — bead‑blasted, matte‑black Type II anodise, laser‑etched | 1 | 12
Total (one‑off) |  | ≈ $52

No built‑in speaker — the Stage feeds your amp / PA. The click is summed in the analog domain (hi‑Z instrument buffer + DAC → balanced line driver), so your instrument is never re‑digitised (no added latency).

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