Build it yourself

Required for both devices

The app reads your head angle with Face-ID tracking and sends pedal commands over Bluetooth. A free App Store release is currently under review; until it goes live you can build and install it from source with the steps below.

1. 1

   What you need

   A Mac with Xcode 15+, an iPhone/iPad with a TrueDepth (Face ID) camera (the Simulator can’t do head tracking), and a free Apple ID to install on your own device.

2. 2

   Get the source & open it

   Clone the repository and open bFaaaPSwitch1.xcodeproj in Xcode.

3. 3

   Set your signing

   In Signing & Capabilities, choose your Team and change the Bundle Identifier to something unique.

4. 4

   Build to your device, then pair & tune

   Run on the connected iPhone/iPad and allow Camera and Bluetooth. Then turn on the device, connect, and preset your threshold (offset) and multiplier — together they set your response speed.

For digital pianos & keyboards

The small, inexpensive version for digital pianos and keyboards. Instead of a motor it switches the sustain electronically through the instrument’s sustain-pedal jack — no motor, no airback. It uses the same iOS app and BLE board as the Pro.

✅ Hardware confirmed by the maker: board = ItsyBitsy nRF52840; a ROHM RU1J002YN logic-level N-MOSFET on GP13 switches the sustain line low-side (no series resistor); power = 2× AA; it starts on RESET.

1. 1

   Before you start

   An Adafruit ItsyBitsy nRF52840 board, a ROHM RU1J002YN N-channel MOSFET, 2× AA batteries, a connector for the sustain-pedal jack (commonly 6.3 mm / TS), and an iPhone/iPad with Face ID.

2. 2

   Flash the BLE board

   Flash the standalone Switch firmware to the nRF52840 (double-tap RESET → UF2 bootloader → upload). Confirm it advertises as bFaaaPSwitch_1…4.

3. 3

   Add the switch & wire to the jack

   Drive the MOSFET from GP13 to open/close the sustain contact (no series resistor), and wire it across the instrument’s sustain-pedal jack (TS tip/sleeve).

4. 4

   Pair & use

   Install the iOS app, connect over Bluetooth, match your instrument’s polarity with the on-type / off-type toggle (n / f), preset offset and multiplier, and play.

For acoustic pianos (grand & upright)

A small motor presses an acoustic piano’s sustain pedal, anchored by an airback air-cushion — nothing is screwed to the piano. The build is a vertical drive column plus the two boards and the airback pump.

🚧 Draft: the electrical schematic (Taguchi) and the mechanical layout (Narusawa) are confirmed; still being finalised are the stepper successor’s firmware (planned motor = a same-size NEMA17, STEP/DIR; the original is end-of-life) and the final printed-part variant.

1. 1

   Print the parts & get the electronics

   Print the frame, push-rod and boxes in PLA+ (0.1–0.2 mm). Order the electronics: Pico, nRF52840, the motor (NEMA17 successor), a +5 V fan, HX711, a MOSFET, a travel-limit slider and a 24 V PSU; plus the frame stock, GT-2-262 belt, T60 pulleys, T10 lead screw, and the WINBAG + electric pump airback.

2. 2

   Assemble the vertical drive

   Build a vertical column: the motor sits beside the screw and couples through the GT-2-262 belt over two T60 pulleys (1:1 — it only offsets the motor, not a reduction); a vertical T10 lead screw carries a push-rod that presses straight down. Add the +5 V cooling fan.

3. 3

   Wire the boards & flash

   Motor serial → Pico GP4/GP5; HX711 → GP2/GP3; air pump on +5 V via MOSFET → GP12; travel slider → ADC0/GP26; BLE ↔ Pico over UART, 24 V to the motor. Then flash both boards (BLE on nRF52, main on the Pico / arduino-pico core).

4. 4

   Mount on the piano + airback

   Place the drive so the push-rod sits over the sustain pedal. Run the air tube from the box’s electric pump to the WINBAG and inflate it against a neighbouring pedal with the PUMP SW to absorb the reaction force — nothing touches the piano’s finish.

5. 5

   Set the force, calibrate, pair & play

   Set the DIP switch for pressing force (20–35 W) and lift (5–20 mm); run the self-calibration (Serial Monitor @ 115200; ~50 mm safety cap). Then pair the app, preset offset and multiplier, calibrate the head-angle zero, and play.