Hardware

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 wiki picks up once you have them.

This page is a quick orientation so the rest of the wiki 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 USB-serial adapter, to flash each module once. See Module Firmware.

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.

---

Next: Module Firmware →