ESP32 ADS-B Flight Display

This project uses an ESP32 to query the adsb.lol API for nearby flights and display the information on an OLED screen. The display shows flight details such as:

• Flight number / Callsign
• Origin and destination airports
• Aircraft type and max seats
• Altitude and distance from your receiver
• Operator classification: PVT (private), COM (commercial), MIL (military)

Notes

• Display uses U8g2 driver with full‑frame buffer and 1‑bit green mono output.
• Pins are configured in config.h and can be changed as needed.
• Power the OLED per vendor specs; logic is 3.3V.

If relays don’t match the expected channel (e.g., COM lights the wrong relay or a different channel energizes on boot):

• Set RELAY_ACTIVE_HIGH according to your module (most 4‑ch boards are active‑LOW = 0).
• Map roles explicitly by overriding in config.h:
  • RELAY_STATUS_PIN, RELAY_COM_PIN, RELAY_PVT_PIN, RELAY_MIL_PIN
• Optionally disable the dedicated status channel: #define RELAY_USE_STATUS_CHANNEL 0.
• Use the test endpoint to push test flight data with specific op class to validate relay wiring:
  • PUT http://<device-ip>/test/closest with body {"ident":"TEST","op":"COM"} (repeat for PVT, MIL)

• U8g2 (by olikraus) for SSD1322 rendering
• ArduinoJson for JSON parsing
• WiFi, WiFiClientSecure, HTTPClient, WebServer (bundled with ESP32 core)

This project uses the adsb.lol API to retrieve live aircraft data.
Endpoints used:

GET /v2/closest/{lat}/{lon}/{radius}

• lat: Latitude in decimal degrees
• lon: Longitude in decimal degrees
• radius: Search radius in kilometers (integer)

Example: https://api.adsb.lol/v2/closest/40.6413/-73.7781/32

Returns the closest aircraft object with fields like:

{
  "hex": "A388AF",
  "flight": "DAL327",
  "r": "N327DU",
  "t": "BCS3",
  "category": "A3",
  "alt_baro": 35000,
  "gs": 445,
  "lat": 40.645,
  "lon": -73.782
}

### Optional MIL classification

To detect military aircraft the device can query `/v2/mil` once per new hex and cache the result for several hours.
- Toggle at compile time with `#define FEATURE_MIL_LOOKUP 0/1` (default: 1).
- If disabled, MIL classification is inferred only from type/seat heuristics.

### Local Test Endpoint

The device exposes a simple test endpoint (when enabled) to push JSON and render without calling the API:

- `PUT http://<device-ip>/test/closest`
  - Body: either a minimal test schema `{ "t": "B738", "ident": "TEST123", "alt": 32000, "dist": 12.3 }` or the full `/v2/closest` schema.
- Toggle at compile time with `#define FEATURE_TEST_SERVER 0/1` (default: 1).

Notes
- JSON parsing is filtered and streamed to minimize RAM (~8 KB doc).
- All network I/O has bounded timeouts; Wi‑Fi reconnects automatically.