ESP32 IR FSO MVP (Day-1 Prototype)

Minimal free-space optical (FSO) digital link for 5 m indoor LOS demo using ESP32 + IR transmitter/receiver.

1) Overview

This implementation is intentionally scoped for a one-day prototype:

• PHY: OOK + Manchester with 38 kHz carrier bursts at default 2 kbps (VS1838B-compatible).
• Framing: preamble + sync + length + payload + CRC16.
• Robustness: adaptive thresholding on RX (EWMA baseline + hysteresis), CRC integrity checks, optional Hamming(7,4) module.
• Host tools: Python GUI for real-time RSSI proxy, BER trend, eye-like overlay, and CSV logging.

Why this design fits your goal:

• Low-cost and off-the-shelf (ESP32 + IR parts).
• Jam-resistant medium (optical LOS, narrow beam).
• Compatible with VS1838B digital IR receiver module using the same host protocol/GUI.

2) Architecture Diagram

flowchart LR
    A[Host GUI Python] <--USB Serial--> B[ESP32 TX]
    A <--USB Serial--> C[ESP32 RX]

    B -->|Manchester OOK IR pulses| D[IR LED + Driver]
    D -->|Free-space optical channel| E[Receiver Front-end]
    E -->|digital/adc sample| C

    C --> F[Sync + Decode + CRC/FEC]
    F --> A

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Repository Layout

• firmware/common/ shared protocol + optional FEC C helpers
• firmware/arduino/ Arduino IDE TX/RX sketches for ESP32-WROOM dev boards
• firmware/tx/ ESP-IDF TX app
• firmware/rx/ ESP-IDF RX app
• host/ Python GUI + serial protocol + logging
• docs/ wiring + test procedure

Detailed documentation:

• docs/code_structure.md code architecture and data flow
• docs/run_guide.md full setup/flash/run instructions
• docs/hardware.md wiring and hardware sizing notes
• docs/test_plan.md validation and BER/range checklist

3) Build & Run

Firmware (Arduino IDE, recommended)

• Open firmware/arduino/tx/tx.ino, select ESP32 Dev Module, upload to TX board.
• Open firmware/arduino/rx/rx.ino, select ESP32 Dev Module, upload to RX board.
• Use 115200 serial monitor baud for both.

Firmware (ESP-IDF, optional legacy)

Build TX:

cd firmware/tx
idf.py set-target esp32
idf.py build
idf.py -p COMx flash monitor

Build RX:

cd firmware/rx
idf.py set-target esp32
idf.py build
idf.py -p COMy flash monitor

Python Host

pip install -r requirements.txt
python host/gui_app.py

4) Quick Wiring (details in docs)

• TX:
  • ESP32 GPIO18 -> gate/base of LED driver transistor (through resistor)
  • IR LED in series with current limit + transistor switch (driven as 38 kHz burst carrier)
  • Shared GND
• RX (VS1838B):
  • VS1838B VCC -> 3V3
  • VS1838B GND -> GND
  • VS1838B OUT -> ESP32 GPIO14 (active-low)

5) Demo Testing

Follow docs/test_plan.md for:

• bench bring-up
• 1 m to 5 m BER sweep
• ambient light stress
• alignment and fallback checks

For complete operator steps from zero to demo, use docs/run_guide.md.

Safety Notes

• Never exceed IR LED pulse current/thermal limits.
• Avoid eye exposure to high-power IR beams.
• Use current-limiting and duty-cycle guardrails in firmware.