How to Build an ESP32 Plane Radar

/*
 * ESP32 Plane Radar
 * Plots live ADS-B aircraft on a GC9A01 1.28-inch round display.
 * First-boot softAP portal (192.168.4.1) stores Wi-Fi + location in NVS.
 * BOOT button (GPIO9) cycles radar range 5 → 10 → 15 → 25 km.
 * Hold BOOT for 3 s to clear saved credentials and relaunch the portal.
 *
 * Inspired by MatixYo's ESP32-Plane-Radar: https://github.com/MatixYo/ESP32-Plane-Radar
 */

#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>
#include <Preferences.h>
#include <HTTPClient.h>
#include <WiFiClientSecure.h>
#include <ArduinoJson.h>
#include <LovyanGFX.hpp>
#include <math.h>

// ── Pin assignments ──────────────────────────────────────────────────────────
#define RADAR_RST   0
#define RADAR_CS    1
#define RADAR_DC    10
#define RADAR_MOSI  3
#define RADAR_SCLK  4
#define BOOT_BUTTON 9

// ── Radar settings ───────────────────────────────────────────────────────────
#define FETCH_INTERVAL_MS 5000
#define HOLD_CLEAR_MS     3000      // hold BOOT this long to wipe credentials
#define AP_SSID           "PlaneRadar-Setup"
#define NVS_NAMESPACE     "planeradar"
#define DISPLAY_SIZE      240
#define DISPLAY_CENTER    120
#define DISPLAY_RADIUS    105       // outermost radar ring

// ── Math helpers ─────────────────────────────────────────────────────────────
static const double DEG2RAD = M_PI / 180.0;

// Returns great-circle distance in kilometres between two lat/lon points.
double haversineKm(double lat1, double lon1, double lat2, double lon2) {
  double dlat = (lat2 - lat1) * DEG2RAD;
  double dlon = (lon2 - lon1) * DEG2RAD;
  double a = sin(dlat / 2) * sin(dlat / 2)
           + cos(lat1 * DEG2RAD) * cos(lat2 * DEG2RAD)
           * sin(dlon / 2) * sin(dlon / 2);
  return 6371.0 * 2.0 * atan2(sqrt(a), sqrt(1.0 - a));
}

// Returns initial bearing in degrees (0 = north, clockwise) from p1 to p2.
double initialBearing(double lat1, double lon1, double lat2, double lon2) {
  double dlon = (lon2 - lon1) * DEG2RAD;
  double y = sin(dlon) * cos(lat2 * DEG2RAD);
  double x = cos(lat1 * DEG2RAD) * sin(lat2 * DEG2RAD)
           - sin(lat1 * DEG2RAD) * cos(lat2 * DEG2RAD) * cos(dlon);
  double bearing = atan2(y, x) / DEG2RAD;
  return fmod(bearing + 360.0, 360.0);
}

// ── LovyanGFX display class ──────────────────────────────────────────────────
class RadarDisplay : public lgfx::LGFX_Device {
  lgfx::Bus_SPI   _bus;
  lgfx::Panel_GC9A01 _panel;
public:
  RadarDisplay() {
    auto busCfg = _bus.config();
    busCfg.spi_host    = SPI2_HOST;
    busCfg.freq_write  = 40000000;
    busCfg.pin_sclk    = RADAR_SCLK;
    busCfg.pin_mosi    = RADAR_MOSI;
    busCfg.pin_miso    = -1;
    busCfg.pin_dc      = RADAR_DC;
    _bus.config(busCfg);
    _panel.setBus(&_bus);

    auto panelCfg = _panel.config();
    panelCfg.pin_cs    = RADAR_CS;
    panelCfg.pin_rst   = RADAR_RST;
    panelCfg.invert    = true;
    panelCfg.rgb_order = true;
    _panel.config(panelCfg);
    setPanel(&_panel);
  }
};

// ── Globals ──────────────────────────────────────────────────────────────────
RadarDisplay display;
Preferences  prefs;
WebServer    configServer(80);

float  radarRangeKm = 10.0f;
double radarLat     = 0.0;
double radarLon     = 0.0;
bool   configMode   = false;

unsigned long lastFetchMs   = 0;
unsigned long bootPressedAt = 0;
bool          bootWasLow    = false;

// ── Forward declarations ─────────────────────────────────────────────────────
void drawRadarShell();
void drawAircraft(float bearingDeg, float distanceKm, const char* label);
void fetchAircraft();
void startConfigPortal();
void handleConfigRoot();
void handleConfigSave();
void showMessage(const char* line1, const char* line2 = nullptr);

// ── Display helpers ──────────────────────────────────────────────────────────
void drawRadarShell() {
  display.fillScreen(TFT_BLACK);
  display.drawCircle(DISPLAY_CENTER, DISPLAY_CENTER, DISPLAY_RADIUS, TFT_GREEN);
  display.drawCircle(DISPLAY_CENTER, DISPLAY_CENTER, 78, TFT_DARKGREEN);
  display.drawCircle(DISPLAY_CENTER, DISPLAY_CENTER, 52, TFT_DARKGREEN);
  display.drawCircle(DISPLAY_CENTER, DISPLAY_CENTER, 26, TFT_DARKGREEN);
  display.drawLine(15, DISPLAY_CENTER, 225, DISPLAY_CENTER, TFT_DARKGREEN);
  display.drawLine(DISPLAY_CENTER, 15, DISPLAY_CENTER, 225, TFT_DARKGREEN);
  display.setTextColor(TFT_WHITE, TFT_BLACK);
  display.setTextSize(1);
  display.drawString("N", 116, 8);
  display.drawString("S", 116, 221);
  display.drawString("W", 6, 116);
  display.drawString("E", 225, 116);
  // Range label bottom-right
  char rangeBuf[8];
  snprintf(rangeBuf, sizeof(rangeBuf), "%dkm", (int)radarRangeKm);
  display.setTextColor(TFT_YELLOW, TFT_BLACK);
  display.drawString(rangeBuf, 195, 218);
}

void drawAircraft(float bearingDeg, float distanceKm, const char* label) {
  if (distanceKm > radarRangeKm) return;
  // bearingDeg is 0=north, rotate so north = up (subtract 90° for screen coords)
  float angle  = (bearingDeg - 90.0f) * DEG_TO_RAD;
  float radius = (distanceKm / radarRangeKm) * (float)DISPLAY_RADIUS;
  int   px     = DISPLAY_CENTER + (int)(cosf(angle) * radius);
  int   py     = DISPLAY_CENTER + (int)(sinf(angle) * radius);
  // Small filled triangle pointing north
  display.fillTriangle(px, py - 5, px - 4, py + 4, px + 4, py + 4, TFT_RED);
  display.setTextColor(TFT_WHITE, TFT_BLACK);
  display.setTextSize(1);
  display.drawString(label,
                     constrain(px + 6, 0, 190),
                     constrain(py - 8, 0, 230));
}

void showMessage(const char* line1, const char* line2) {
  display.fillScreen(TFT_BLACK);
  display.setTextColor(TFT_WHITE, TFT_BLACK);
  display.setTextSize(1);
  display.drawString(line1, 20, 110);
  if (line2) display.drawString(line2, 20, 125);
}

// ── Config portal ────────────────────────────────────────────────────────────
// Small HTML form served over softAP — stores SSID/password/lat/lon in NVS.
// This replaces WiFiManager to keep binary size under the 1 280 KB app partition.
static const char CONFIG_HTML[] PROGMEM = R"rawhtml(
<!DOCTYPE html><html><head>
<meta name='viewport' content='width=device-width,initial-scale=1'>
<title>PlaneRadar Setup</title>
<style>body{font-family:sans-serif;max-width:380px;margin:40px auto;padding:0 16px}
input{width:100%;box-sizing:border-box;padding:8px;margin:6px 0 14px;font-size:15px}
button{width:100%;padding:10px;background:#27ae60;color:#fff;border:none;font-size:16px;cursor:pointer}
h2{margin-bottom:4px}p{color:#555;font-size:13px;margin-top:0}</style>
</head><body>
<h2>PlaneRadar Setup</h2>
<p>Enter your Wi-Fi details and the coordinates for the radar centre.</p>
<form method='POST' action='/save'>
<label>Wi-Fi Name (SSID)</label><input name='ssid' required>
<label>Wi-Fi Password</label><input name='pass' type='password'>
<label>Latitude (e.g. 52.3676)</label><input name='lat' required placeholder='52.3676'>
<label>Longitude (e.g. 4.9041)</label><input name='lon' required placeholder='4.9041'>
<button type='submit'>Save &amp; Connect</button>
</form>
</body></html>
)rawhtml";

static const char SAVED_HTML[] PROGMEM = R"rawhtml(
<!DOCTYPE html><html><head>
<meta name='viewport' content='width=device-width,initial-scale=1'>
<title>Saved</title>
<style>body{font-family:sans-serif;max-width:380px;margin:40px auto;padding:0 16px}</style>
</head><body>
<h2>Saved!</h2>
<p>The radar is connecting to your Wi-Fi. You can close this page.</p>
</body></html>
)rawhtml";

void handleConfigRoot() {
  configServer.send(200, "text/html", CONFIG_HTML);
}

void handleConfigSave() {
  String ssid = configServer.arg("ssid");
  String pass = configServer.arg("pass");
  String lat  = configServer.arg("lat");
  String lon  = configServer.arg("lon");

  prefs.begin(NVS_NAMESPACE, false);
  prefs.putString("ssid", ssid);
  prefs.putString("pass", pass);
  prefs.putDouble("lat",  lat.toDouble());
  prefs.putDouble("lon",  lon.toDouble());
  prefs.end();

  configServer.send(200, "text/html", SAVED_HTML);
  delay(1500);
  ESP.restart();
}

void startConfigPortal() {
  configMode = true;
  WiFi.mode(WIFI_AP);
  WiFi.softAP(AP_SSID);
  Serial.print("Config portal at: ");
  Serial.println(WiFi.softAPIP());

  configServer.on("/",     HTTP_GET,  handleConfigRoot);
  configServer.on("/save", HTTP_POST, handleConfigSave);
  configServer.begin();

  showMessage("PlaneRadar-Setup", "192.168.4.1");
}

// ── Aircraft fetch ────────────────────────────────────────────────────────────
void fetchAircraft() {
  if (WiFi.status() != WL_CONNECTED) return;

  // opendata.adsb.fi: dist is nautical miles; convert km → nm (1 nm = 1.852 km)
  // adsb.fi is HTTPS-only (plain HTTP gets a 301 the ESP32 HTTPClient will
  // not follow). setInsecure() skips certificate validation: this is public,
  // read-only flight data, and the C3's 1.25 MB app partition has no room
  // for a CA bundle on top of the TLS stack.
  float nm = radarRangeKm / 1.852f;
  WiFiClientSecure client;
  client.setInsecure();
  String url = "https://opendata.adsb.fi/api/v3/lat/"
             + String(radarLat, 5)
             + "/lon/"
             + String(radarLon, 5)
             + "/dist/"
             + String(nm, 1);

  HTTPClient http;
  http.begin(client, url);
  http.setTimeout(4000);
  int code = http.GET();

  if (code == HTTP_CODE_OK) {
    // Parse JSON — static allocation avoids heap fragmentation
    JsonDocument doc;
    DeserializationError err = deserializeJson(doc, http.getStream());
    if (err) {
      Serial.printf("JSON error: %s\n", err.c_str());
      http.end();
      return;
    }

    drawRadarShell();
    int plotted = 0;

    for (JsonObject plane : doc["ac"].as<JsonArray>()) {
      if (!plane["lat"].is<double>() || !plane["lon"].is<double>()) continue;

      double acLat = plane["lat"].as<double>();
      double acLon = plane["lon"].as<double>();

      double distKm   = haversineKm(radarLat, radarLon, acLat, acLon);
      double bearDeg  = initialBearing(radarLat, radarLon, acLat, acLon);

      if (distKm > radarRangeKm) continue;   // outside current range

      // Label preference: flight callsign → ICAO hex → fallback "AC"
      const char* label = plane["flight"] | plane["hex"] | "AC";

      drawAircraft((float)bearDeg, (float)distKm, label);
      plotted++;
    }

    Serial.printf("Plotted %d aircraft within %.0f km\n", plotted, radarRangeKm);
  } else {
    Serial.printf("HTTP error: %d\n", code);
  }
  http.end();
}

// ── Setup ─────────────────────────────────────────────────────────────────────
void setup() {
  Serial.begin(115200);
  pinMode(BOOT_BUTTON, INPUT_PULLUP);

  display.init();
  display.setRotation(0);
  display.setTextSize(1);
  drawRadarShell();

  // Load saved credentials from NVS
  prefs.begin(NVS_NAMESPACE, true);
  String savedSsid = prefs.getString("ssid", "");
  String savedPass = prefs.getString("pass", "");
  radarLat         = prefs.getDouble("lat", 0.0);
  radarLon         = prefs.getDouble("lon", 0.0);
  prefs.end();

  if (savedSsid.length() == 0) {
    Serial.println("No credentials — starting config portal");
    startConfigPortal();
    return;
  }

  showMessage("Connecting to WiFi...", savedSsid.c_str());
  WiFi.mode(WIFI_STA);
  WiFi.begin(savedSsid.c_str(), savedPass.c_str());

  unsigned long t0 = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - t0 < 15000) {
    delay(250);
  }

  if (WiFi.status() != WL_CONNECTED) {
    Serial.println("Wi-Fi failed — starting config portal");
    startConfigPortal();
    return;
  }

  Serial.printf("Connected. IP: %s  Lat: %.4f  Lon: %.4f\n",
                WiFi.localIP().toString().c_str(), radarLat, radarLon);
  drawRadarShell();
}

// ── Loop ──────────────────────────────────────────────────────────────────────
void loop() {
  if (configMode) {
    configServer.handleClient();
    return;
  }

  // BOOT button: short press cycles range; hold 3 s clears credentials
  bool bootLow = (digitalRead(BOOT_BUTTON) == LOW);

  if (bootLow && !bootWasLow) {
    bootPressedAt = millis();
    bootWasLow = true;
  }

  if (!bootLow && bootWasLow) {
    unsigned long held = millis() - bootPressedAt;
    bootWasLow = false;

    if (held >= HOLD_CLEAR_MS) {
      // Long press: wipe saved credentials and reboot into portal
      Serial.println("Long press — clearing credentials");
      prefs.begin(NVS_NAMESPACE, false);
      prefs.clear();
      prefs.end();
      delay(200);
      ESP.restart();
    } else {
      // Short press: cycle range
      if      (radarRangeKm ==  5) radarRangeKm = 10;
      else if (radarRangeKm == 10) radarRangeKm = 15;
      else if (radarRangeKm == 15) radarRangeKm = 25;
      else                         radarRangeKm =  5;
      Serial.printf("Range → %.0f km\n", radarRangeKm);
      drawRadarShell();
    }
  }

  // Fetch every FETCH_INTERVAL_MS
  if (millis() - lastFetchMs >= FETCH_INTERVAL_MS) {
    lastFetchMs = millis();
    fetchAircraft();
  }
}

// Run this and build other cool things at schematik.io