ESP32 Bicycle Speed Sensor → Unreal Engine Integration

This project provides firmware for an ESP32 (Arduino framework via PlatformIO) to measure bicycle wheel speed using a Hall-effect sensor (or reed switch) and stream speed to a PC over USB Serial. It also includes Unreal Engine C++ code to read the stream and expose the current speed to Blueprints.

Hardware

• ESP32: esp32dev board profile
• Sensor: Hall-effect sensor or reed switch
• Magnet(s): Mounted on wheel spoke(s)

Wiring

Bike Magnet(s) → Hall Sensor → ESP32

Hall/Vout  → GPIO 4 (default)
VCC        → 3V3
GND        → GND

ESP32 pin is configured with INPUT_PULLUP. For open-drain sensors, ensure they pull to GND when triggered.

Build (Firmware)

1. Install PlatformIO (VS Code extension or CLI).
2. Connect ESP32 via USB.
3. From this folder, build and upload:

pio run -t upload
pio device monitor

Default config (overridable in platformio.ini):

• CONFIG_DEFAULT_WHEEL_CIRCUM_MM=2105 (700x35c typical) → circumference in mm
• CONFIG_DEFAULT_MAGNETS_PER_REV=1
• CONFIG_DEFAULT_HALL_PIN=4

Telemetry Format (USB Serial)

CSV line at ~30 Hz:

mps,kmh,rpm,pulses,dt_us,t_ms
0.000,0.000,0.00,0,33000,123456

Fields:

• mps: meters per second (smoothed EMA)
• kmh: kilometers per hour (smoothed)
• rpm: wheel revolutions per minute
• pulses: pulses detected in the last integration window
• dt_us: microseconds of the last window
• t_ms: device uptime (ms)

Unreal Engine Integration (Windows)

Included under unreal/BikeSpeed/ is a minimal plugin:

• UBikeSpeedComponent (Blueprint component) exposes CurrentSpeedKmh and CurrentSpeedMps.
• Windows-only serial reader uses Win32 API to open a COM port (e.g. COM5) and parse the CSV.

Setup:

1. Copy unreal/BikeSpeed into your UE project's Plugins/ folder.
2. Enable the plugin in your project.
3. In Project Settings → Plugins → BikeSpeed, set the COM port (or in code).
4. Add BikeSpeedComponent to your pawn/actor and bind tick to update speed.

Serial Port Tips on Windows:

• Find COM port via Device Manager under "Ports (COM & LPT)".
• Use the same baud as firmware (115200).

BLE Option (Future)

The firmware contains a TransportBLE placeholder. To minimize initial complexity and latency variance, USB Serial is the default. BLE can be added later if needed.

Repository Layout

include/
  Config.h
  HallSensor.h
  SpeedCalculator.h
  TransportSerial.h
  TransportBLE.h
src/
  main.cpp
  HallSensor.cpp
  SpeedCalculator.cpp
unreal/
  BikeSpeed/ (UE plugin: module, component, serial reader)
platformio.ini
README.md

Safety Notes

• Test on a stand before riding.
• Securely mount the magnet and sensor.