Overview
For builders seeking the traditional aesthetic of a draw-stop console, PIPE 2C offers I2C knob controllers with PCB-based push-pull position sensing using a PCA9555 16-bit I/O expander. Each knob engages or disengages a stop rank with a satisfying tactile click.
Key Features
- PCA9555 I/O expander — 16 inputs per chip for reliable, bounce-free position sensing
- I2C chainable — Standard 4-wire Qwiic/STEMMA QT connectors
- PCB-based push-pull detection — Button series on the PCB senses knob position
- Customizable face plates — Customizer app for knob front plate design in development
- Solderless assembly — Plug-in connections throughout
Schematic
PCB Layout
Bill of Materials
| Component | Designator | Quantity | Description |
|---|---|---|---|
| PCA9555PW,118 | U2 | 1 | 16-bit I2C I/O expander (TSSOP-24) |
| KH-2.54FH90-1X4P | U1 | 1 | 4-pin right-angle female header |
| PZ254R-11-04P | H3 | 1 | 4-pin male header |
| 10kΩ | R6, R16, R17, R18 | 4 | Pull-up/pull-down resistors (0805) |
| 4.7kΩ | R1, R4 | 2 | I2C pull-up resistors (0805) |
Connection
Each knob controller module supports multiple knobs on a single I2C-connected PCB, maintaining the chainable architecture of the PIPE 2C ecosystem.
Open Source
Full schematics, PCB layout, and BOM available on OSHWLab:
3D Printed Parts
Full 3D-printed knobs and mechanism. Metal spring-based mechanism in the works.
| Parameter | Recommendation |
|---|---|
| Material | PLA or PETG |
| Layer height | 0.2mm |
| Infill | 40% minimum |
| Supports | Required for shaft |
| Print time | ~2 hours per knob assembly |