Hardware

The physical display is a wall of split-flap modules, one per character cell. The module design — the mechanics, the circuit board, and the original bus protocol — is by Adam G Makes, and the build is documented in his repository:

👉 github.com/adamgmakes/SplitFlapDisplay

The circuit board, the 3D-printed parts, the bill of materials and the assembly steps live there. Start with Adam's repo and his YouTube channel to build or source the modules; this guide picks up once you have them.

This page is a quick orientation so the rest of the guide makes sense — it is not a substitute for Adam's build docs.

What one module is

Each character cell is a small, self-contained board carrying:

• an ATtiny1616 microcontroller (3.3 V logic) that runs the module firmware;
• a 28BYJ-48 stepper motor turning the flap reel, through a ULN2003 driver, from a separate 12 V motor supply (the motor is not powered from the logic rail);
• a Hall-effect sensor that finds a magnet on the reel to establish the home position;
• a half-duplex RS-485 transceiver, with the driver-enable line on a GPIO;
• a DIN-rail clip and four pogo pins on the underside — the module's only electrical connection (see below).

The reel carries the printed flaps — letters, digits, punctuation and a set of solid colour flaps (red, orange, yellow, green, blue, purple, white). A default reel has 64 flaps; index 0 is the blank/home flap.

How modules connect

There is no wiring between modules. Each module clips onto a DIN rail, and four pogo pins on its underside press against a conductor rail carrying the four shared lines: power (12 V), ground, and the two RS-485 bus signals (A/B). Mounting a module is connecting it — snap it onto the rail and it's on the bus.

A single controller is the bus master. In this project that controller is the SplitFlap Gateway (an ESP32); the bus runs at 9600 baud, 8N1.

    [M0]    [M1]    [M2]    [M3]    [M4]   … up to 255 modules,
   ══╪╪══════╪╪══════╪╪══════╪╪══════╪╪══   each clipped onto the DIN rail;
   ────────────────────────────────────    4 pogo pins per module contact the
   conductor rail:  12V · GND · RS-485 A · RS-485 B  ──── to the Gateway (ESP32)

Every module runs the same firmware binary — there is nothing to change per module before flashing. A module's identity (its bus ID, e.g. "module 0") is assigned later, at runtime, by provisioning. That's the key difference from Adam's original firmware, where each module's ID was compiled in; see the Module Firmware page.

What you need to drive them

Part	Notes
Split-flap modules	However many cells you want — a 3 × 15 wall is 45. Built/sourced per Adam's repo.
DIN rail + conductor rail	One per row. The modules clip on; the conductor rail distributes 12 V, GND and the two bus signals to their pogo pins. Per Adam's design.
A 12 V supply	Sized for your module count (the steppers are the load). See Adam's BOM.
The SplitFlap Gateway board	A Waveshare ESP32-S3-RS485-CAN — it has the RS-485 transceiver on board.
A SerialUPDI programmer	A cheap CH340 USB-serial adapter with one Schottky diode soldered on — build it yourself in ten minutes. It powers the module while flashing, so modules can be flashed on the bench before they go on the rail. See Flashing Modules.

The no-hardware option

Don't want to build anything mechanical? The Matrix Gateway renders virtual split-flap modules on an LED matrix — no modules, no RS-485, no steppers — and behaves exactly like a real gateway to everything downstream. It's the fastest way to try the whole stack.

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Next: Module Firmware →