BTT SFS 2.0 + RP2040-Zero Receptacle

## Description

A complete, self-contained filament sensor module in a single printed part — one USB cable and you're wired.

This receptacle houses a BigTreeTech Smart Filament Sensor 2.0 and a Waveshare RP2040-Zero flashed as a standard Klipper USB MCU. The pico reads both SFS signals and exposes them to Klipper as native objects:

- filament_switch_sensor → filament presence (runout)

- filament_motion_sensor → actual movement (clog, slip, under-extrusion detection)

### Why a dedicated MCU?

- Zero pins needed on your main or toolhead board

- One USB cable — no signal wires across the printer

- Plug-and-play — move it between machines, or retrofit a printer never wired for it

- Electrically self-contained: the SFS runs on 3.3 V from the pico

### Receptacle features

- Mounts on a 2020 extrusion (tab with 2× M3 holes for T-nuts)

- Screws onto the SFS mounting face — 2× M3×12 button-head, flat counterbores included

- RP2040-Zero cavity with a USB-C opening cut to the real connector contour

- BOOT/RESET button access holes (3×5 mm ovals)

- 2× M6 filament ports for the PC4-M6 fittings supplied with the SFS

### Assembly

1. Seat the pico in its cavity (USB-C through the end-wall opening) and **hot-glue it

   at the four corners** — simple, firm, and serviceable.

2. Screw the receptacle to the SFS with 2× M3×12 button-head.

3. Mount on the 2020 with M3 + T-nuts.

4. Run the PTFE ID2/OD4 guides all the way into the SFS bore on both ports —

   mandatory when pushing filament, otherwise it buckles at the junction.

### Wiring & Klipper config

⚠ Power the SFS at 3.3 V only — the RP2040 is not 5 V-tolerant.

Motion → GP0, switch → GP1, internal pull-ups.

Full wiring guide, Klipper/Katapult flashing steps and a ready-to-include

sfs.cfg are on GitHub:

https://github.com/Nitrooxyde/SFS2-RP2040-Klipper

### BOM

| Qty | Part |

|-----|------|

| 1 | BigTreeTech SFS 2.0 |

| 1 | Waveshare RP2040-Zero |

| 2 | M3×12 button-head screws |

| 2 | M3 screws + T-nuts (2020 mounting) |

| 2 | PC4-M6 fittings (supplied with the SFS) |

| — | PTFE tube ID2/OD4 |

| 1 | USB-C cable |

| — | Hot glue |

Tested for real on a Voron 2.4. STL verified watertight (59,488 facets).

Footprint: 69 × 48 × 25 mm.

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## Print settings (structured fields)

- Printer: any (designed on a Voron 2.4)

- Nozzle: 0.4 mm

- Layer height: 0.2 mm

- Material: ABS / ASA (PETG works)

- Perimeters/walls: 4

- Infill: 30–40 %

- Supports: only on the USB-C / port / button openings, depending on orientation

- Brim: optional