FoxilloScope (STM32G474 Oscilloscope)

An accessible, wireless oscilloscope built around low-cost development hardware: the ST Nucleo-G474RE board and an M5Stamp C3U (ESP32-C3) module.

• Bipolar signal measurement
• Dual-channel
• Up to 8 MHz sampling rate
• 12-bit resolution
• The user interface runs in a web browser on desktop and mobile devices
• Communication via Wi-Fi or Bluetooth Low Energy (BLE). Bluetooth requires a compatible browser (e.g., Google Chrome).
• No installable application required

The goal of this project is to turn inexpensive, readily available development components into a practical, portable oscilloscope with live-streaming over Wi-Fi or Bluetooth LE — requiring minimal soldering and no custom PCBs.

💡 Developer Note: For firmware compilation, hardware debug configurations, jumper setups, and local debug servers, see the Developer & Contributor Guide.

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Key Features & Hardware Design

• Affordable Hardware: Total hardware cost is under €25 / $30 (minimal soldering, no custom PCBs needed)
  • Analog front-end (AFE) built on the ST Nucleo-G474RE board – handling signal capture and triggering
  • M5Stamp C3U handles wireless connectivity and hosts the web server
  • Signal conditioning built with six Schottky diodes (BAS40-04 dual-diodes or equivalent) and five resistors
  • Inexpensive oscilloscope probes (not included in BOM)
• Bipolar Signal Measurement: On-chip analog front-end (AFE) supports true bipolar AC/DC signal measurements (both positive and negative voltages) around virtual ground.

  ⚠️ Important Grounding Notice: Users must not connect probe ground clips to the board's GND pins. Always connect probe ground clips to the board's dedicated Virtual Ground output. This provides a clean mid-rail reference for bipolar measurements and prevents shorting power rails.

• Input Voltage Range: Measurable range −1.65 V to +1.65 V (1:10 attenuating oscilloscope probes recommended); safe input range −30 V to +30 V.
• Input Signal Protection: A resistor and diode protection network protects MCU inputs against out-of-range signal spikes.
• Multi-Transport Web UI: Single-page web dashboard accessible via Wi-Fi (WebSockets), Bluetooth LE (WebBluetooth), or USB (WebSerial).

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Quick Start (Flashing & Operation)

Hardware Setup & Assembly

All hardware documentation, board modification guides, jumper configurations, and soldering diagnostics have been consolidated into the Hardware Guide (docs/HARDWARE.md):

1. Board Modding First

   1. Solder bridges (SB17/SB23, SB18/SB22, JP8, JP6).
   2. Wiring Verification (pin_check) — Diagnostic test to check proper wiring.
   3. Soldering protection network

2. Jumper Configuration — Jumper settings for Production and Development modes.

3. ESP32 Gateway Module — Power, UART connections, and RGB status LED table.

4. Flash the STM32 Firmware:

   1. Connect the Nucleo board to your computer via USB (in development jumper mode). A virtual USB drive will appear.
   2. Copy FoxilloScope-Production.bin from the latest release assets onto the virtual drive.
   3. Configure jumpers for Production mode for standalone use.

5. Flash the ESP32 Gateway (M5Stamp C3U):

   1. Connect the M5Stamp C3U to your computer via USB.
   2. Use the Foxilloscope ESP32 Web Flasher to upload the gateway firmware.

6. Connect Probes:

   1. Attach oscilloscope probes to Channel A / Channel B inputs.
   2. Connect probe ground clips to Virtual Ground (VGND) (never to board GND!).

7. Connect & Measure:

   1. Wi-Fi: Connect to FoxilloScope-xxxx Wi-Fi network and open http://f-scope.local/ (or http://192.168.4.1/).
   2. Bluetooth LE: Open http://f-scope.local/ in Chrome, click the Bluetooth icon, and pair with F-SCOPE-xxxx.
   3. Wi-Fi Credentials Setup: Open http://f-scope.local/wifi to configure your home Wi-Fi network.
   4. Device Label (optional): Open Sticker Generator and enter the device ID (xxxx, last four hex digits of the ESP32 MAC).

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Deployment & Web Access

1. Wireless Gateway Mode (Default)

Connect your computer, phone, or tablet to the ESP32 gateway (either directly via its FoxilloScope AP or through your local Wi-Fi network) and open:

http://f-scope.local/

The ESP32 serves the web frontend and streams data in real time via WebSockets.

2. Standalone CDN / GitHub Pages Mode

The web app can also be hosted on any static HTTPS server (e.g. GitHub Pages). In this mode, the browser connects directly to the hardware via:

• WebBluetooth: Connect wirelessly over BLE.
• WebSerial: Connect directly over USB at 460,800 baud.

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Documentation & References

• Hardware Setup & Assembly Guide – Board solder bridge modifications, jumpers, external circuit, and pin_check verification.
• Developer & Contributor Guide – Firmware compilation, debug hardware jumper configurations, Python debug server, and tools used.
• Physical Wiring Diagram: docs/wiring_diagram.html
• Subsystem Architecture References:
  • STM32 Firmware Architecture: AGENTS.md
  • ESP32 Gateway Architecture: esp32-gateway/AGENTS.md
  • Web Frontend Architecture: html/AGENTS.md