The rocker tab is the most recognizable control surface on a pipe organ console. PIPE 2C’s rocker tab controller brings this traditional interface into the modern era with I2C-based chainable electronics and integrated LED illumination.
Each module provides 8 rocker tab positions with both dimmable and standard yellow indicator lights. Modules feature standard I2C connectors on both ends for daisy-chaining, plus optional serial headers for easy connection. A three-manual organ with 60 stops simply uses 8 modules connected in series — no complex wiring harnesses, no multiplexer configuration, no soldering.
Video Tour
Key Features
- 8 positions per module — Each rocker tab has its own switch and LED indicator
- Dimmable illumination — Individual dimmable lights plus standard yellow indicators show which stops are engaged
- Thinner margins — Compact PCB layout for tight console spacing
- Up to 64 modules (512 stops) — Massive scalability on a single I2C bus
- I2C chainable — Standard 4-wire Qwiic/STEMMA QT connectors for plug-and-play daisy chaining
- Easy serial connection — Optional headers for serial hookup
- Solderless assembly — No soldering required; all connections are plug-in
How It Works
A rocker tab is a two-position control—rock it up to draw a stop, rock it down to retire it—so eight tabs need 16 switch inputs, plus 8 outputs to drive the indicator LEDs. That’s 24 lines of I/O, more than a single expander provides, so each module carries two PCA9555 16-bit I2C I/O expanders: one reads the rocker switches while the other drives the illumination. As with the rest of the PIPE 2C family, there is no microcontroller and no firmware on board—the host reads and writes the expanders directly over I2C.
An on-board trimmer sets the LED brightness, so the engaged-stop indicators glow at a level that matches the ambient light of your console rather than washing it out.
Addressing & scale
Each module is given a unique bus address with its DIP switches, and the two expanders occupy adjacent addresses. Because a single I2C bus can host many devices, you can chain up to 64 modules—512 stops—on one bus. A three-manual instrument with 60 stops is simply 8 modules in series: no ribbon cables, no multiplexer boards, no soldering.
Solderless chaining
Standard 4-wire I2C connectors on both ends (Qwiic / STEMMA QT compatible) carry power, clock and data from module to module. Optional serial headers provide an alternative hookup for builders who prefer it. Plug the modules together in a line and the whole stop-jamb is wired.
Role in Your Organ
Rocker tabs (or “stop tabs”) select the stops—the individual voices, or ranks of pipes, that make up the organ’s sound. Drawing a tab adds that rank to whatever you play; the lit indicator tells you at a glance which voices are active. Grouped across the stop-jamb of a console, banks of rocker tabs are how the organist builds and changes the registration of the instrument.
Bill of Materials
| Component | Designator | Qty | Description |
|---|---|---|---|
| PCA9555PW,118 | U2, U6 | 2 | 16-bit I2C I/O expander (TSSOP-24) |
| Rocker tab switch | SW1–SW16 | 16 | Two positions per tab (8 lighted tabs) |
| Indicator LED | LED1–LED8 | 8 | Per-tab stop-engaged indicator |
| DIP switch | U4, U7 | 2 | I2C address select |
| SM04B-SRSS-TB | CN1, CN2 | 2 | JST 4-pin I2C connector (in / out) |
| Trimmer | — | 1 | LED brightness adjust |
| Header | H3, U5 | 2 | Optional serial connection |
| 0603 / 0805 resistors | R1–R43 | — | LED current-limit & I2C pull-ups |
Customizer Software
A companion application (currently in development) will enable custom engraving specifications for each rocker tab name tag. Builders will be able to:
- Design and print professional stop labels
- Choose from traditional organ typography styles
- Export designs for laser engraving or UV printing on acrylic faces
- Preview the complete console layout before building
Connection
3D Printed Parts
Each rocker tab module is complemented by a set of 3D-printable enclosure and mounting parts designed to integrate the electronics into your console. STL files are provided for the rocker tab frames, mounting brackets, and face plate holders. Print in PLA or PETG on any standard FDM printer.
Open Source
Schematics, PCB layouts and 3D print files are available on the OpenPipes GitHub.