Marlin USB Resonance Tester

Measure your 3D printer’s mechanical resonance over USB (ADXL345 on an RP2040 “USB accelerometer” board) and use the built-in web UI to:

• Flash the firmware (UF2)
• Stream accelerometer samples over the browser’s Web Serial API
• View a live spectrogram / peak frequency
• Simulate data without hardware
• Optimise Marlin FT_MOTION input shaper coefficients from measured max-hold spectra

Live app (GitHub Pages): https://dbuezas.github.io/usb-Input-shaper-calibrator/

Source repository: https://github.com/dbuezas/usb-Input-shaper-calibrator

What’s in this repo

• src/main.cpp: RP2040 firmware that reads an ADXL345 over SPI and streams packed samples over USB serial.
• platformio.ini: PlatformIO configuration for board = pico (Earle Philhower Arduino core).
• UI/: React + Vite web app (deployed to GitHub Pages via .github/workflows/deploy.yaml).

Requirements

• A Chromium-based browser with Web Serial support: Chrome, Edge, Opera.
• Hardware (optional): an RP2040 + ADXL345 “USB accelerometer” board (e.g. Mellow Fly ADXL345 USB-C).

Quick start (recommended)

1. Open the web app.
2. Install firmware → download firmware.uf2.
3. Put the RP2040 into bootloader mode (hold BOOT while plugging in) and drag-and-drop the UF2 onto the RPI-RP2 drive.
4. Measure axis → click Connect and pick the serial device.
5. Use Simulate if you want to try the UI without hardware.
6. Optimize shaper → run Auto optimise to get suggested shaper taps.

Building the firmware (PlatformIO)

This is only needed if you want to build your own UF2 instead of using the one bundled in the UI.

pio run

The firmware:

• Targets RP2040 (board = pico)
• Reads the ADXL345 via bit-banged SPI
• Streams samples over USB serial at 230400 baud (UI expects the same)

Running the UI locally

cd UI
pnpm install
pnpm dev

Then open the printed local URL.

Notes / troubleshooting

• USB-C ↔ USB-C cables: some boards don’t have CC resistors and won’t enumerate. Use USB-A → USB-C (or an A-port adapter) if connection is flaky.
• If Connect stays on “Connecting”, check you flashed the UF2, selected the right port, and the device is streaming.

Screenshots