How to Build a Tiny OLED Desk Command Centre

// Tiny OLED Desk Command Centre
// SSD1306 0.96" I2C OLED — shows time (NTP), weather (Open-Meteo), and
// accepts short messages sent from a browser on the LAN.
// Edit WIFI_SSID / WIFI_PASSWORD and the location / timezone constants below.

#include <Arduino.h>
#include <Wire.h>
#include <WiFi.h>
#include <WebServer.h>
#include <HTTPClient.h>
#include <time.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <ArduinoJson.h>

// ── User-editable constants ─────────────────────────────────────────────────

const char* WIFI_SSID     = "YOUR_WIFI_NAME";      // ← edit
const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD";  // ← edit

// Timezone offset from UTC in seconds (e.g. UTC+1 = 3600, UTC-5 = -18000)
const long  TZ_OFFSET_SEC  = 0;
// Daylight-saving offset in seconds (1 hour = 3600; set 0 if your region has none)
const int   DST_OFFSET_SEC = 3600;

// Open-Meteo location (decimal degrees)
const float WEATHER_LAT = 51.5074f;   // London default — edit to your location
const float WEATHER_LON = -0.1278f;

// ── Pin definitions ─────────────────────────────────────────────────────────
#define SDA_PIN 21
#define SCL_PIN 22

// ── Display config ──────────────────────────────────────────────────────────
#define SCREEN_WIDTH  128
#define SCREEN_HEIGHT  64
#define OLED_RESET     -1   // no reset pin wired
#define OLED_I2C_ADDR 0x3C

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// ── Web server ──────────────────────────────────────────────────────────────
WebServer server(80);

// ── State ───────────────────────────────────────────────────────────────────
String  weatherLine    = "weather...";   // e.g. "12°C Partly cloudy"
bool    weatherOk      = false;

String  customMessage  = "";
unsigned long msgShowUntil = 0;          // millis() deadline for custom message

unsigned long lastWeatherFetch = 0;
unsigned long lastClockUpdate  = 0;
unsigned long lastIpPrint      = 0;

const unsigned long WEATHER_INTERVAL = 10UL * 60UL * 1000UL; // 10 minutes
const unsigned long CLOCK_INTERVAL   = 1000UL;                // 1 second
const unsigned long IP_PRINT_INTERVAL = 30UL * 1000UL;        // 30 seconds
const unsigned long MSG_DISPLAY_MS   = 8000UL;                 // 8 seconds

// ── Forward declarations ────────────────────────────────────────────────────
void connectWiFi();
void fetchWeather();
void updateDisplay();
void handleRoot();
void handleSend();
void showMessage(const String& msg);
String buildTimeLine();

// ── setup() ─────────────────────────────────────────────────────────────────
void setup() {
  Serial.begin(115200);
  delay(200);
  Serial.println("OLED Desk Command Centre starting");

  Wire.begin(SDA_PIN, SCL_PIN);

  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_I2C_ADDR)) {
    Serial.println("SSD1306 not found — check wiring on GPIO21/22");
    // Keep running so Serial diagnostics stay alive; display calls become no-ops
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("Connecting to Wi-Fi");
  display.display();

  connectWiFi();

  // Sync time via NTP
  configTime(TZ_OFFSET_SEC, DST_OFFSET_SEC, "pool.ntp.org", "time.nist.gov");
  Serial.println("NTP sync requested");

  // Web server routes
  server.on("/",     HTTP_GET,  handleRoot);
  server.on("/send", HTTP_POST, handleSend);
  server.begin();
  Serial.println("HTTP server started on port 80");

  // First weather fetch
  fetchWeather();

  updateDisplay();
}

// ── loop() ──────────────────────────────────────────────────────────────────
void loop() {
  server.handleClient();

  unsigned long now = millis();

  // Reconnect if dropped
  if (WiFi.status() != WL_CONNECTED) {
    connectWiFi();
  }

  // Periodic weather refresh
  if (now - lastWeatherFetch >= WEATHER_INTERVAL) {
    fetchWeather();
    lastWeatherFetch = now;
  }

  // Clock tick
  if (now - lastClockUpdate >= CLOCK_INTERVAL) {
    lastClockUpdate = now;
    // Only refresh display when no custom message is showing
    if (now >= msgShowUntil) {
      updateDisplay();
    }
  }

  // Clear custom message when timer expires and return to dashboard
  if (customMessage.length() > 0 && now >= msgShowUntil) {
    customMessage = "";
    updateDisplay();
  }

  // Repeat IP to Serial so the user can find the device
  if (now - lastIpPrint >= IP_PRINT_INTERVAL) {
    lastIpPrint = now;
    if (WiFi.status() == WL_CONNECTED) {
      Serial.print("Device IP: http://");
      Serial.println(WiFi.localIP());
    }
  }
}

// ── Wi-Fi ────────────────────────────────────────────────────────────────────
void connectWiFi() {
  Serial.printf("Connecting to %s", WIFI_SSID);
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

  display.clearDisplay();
  display.setCursor(0, 0);
  display.println("Connecting...");
  display.display();

  unsigned long start = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - start < 20000UL) {
    delay(500);
    Serial.print(".");
  }

  if (WiFi.status() == WL_CONNECTED) {
    Serial.println();
    Serial.print("Connected. IP: ");
    Serial.println(WiFi.localIP());
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("Connected!");
    display.print("IP: ");
    display.println(WiFi.localIP().toString());
    display.display();
    delay(2000);
  } else {
    Serial.println("\nWi-Fi connection failed — retrying in main loop");
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("Wi-Fi failed");
    display.println("Retrying...");
    display.display();
  }
}

// ── Weather fetch (Open-Meteo, no key required) ──────────────────────────────
void fetchWeather() {
  if (WiFi.status() != WL_CONNECTED) {
    weatherLine = "weather unavailable";
    weatherOk   = false;
    return;
  }

  char url[200];
  snprintf(url, sizeof(url),
    "http://api.open-meteo.com/v1/forecast"
    "?latitude=%.4f&longitude=%.4f"
    "&current_weather=true"
    "&temperature_unit=celsius",
    WEATHER_LAT, WEATHER_LON);

  HTTPClient http;
  http.begin(url);
  http.setTimeout(8000);
  int code = http.GET();

  if (code == 200) {
    String body = http.getString();
    // Parse with ArduinoJson — stream-style to keep heap use low
    StaticJsonDocument<512> doc;
    DeserializationError err = deserializeJson(doc, body);
    if (!err) {
      float temp      = doc["current_weather"]["temperature"].as<float>();
      int   wmoCode   = doc["current_weather"]["weathercode"].as<int>();

      // Map a handful of WMO codes to short labels
      const char* cond = "Unknown";
      if      (wmoCode == 0)                    cond = "Clear";
      else if (wmoCode <= 3)                    cond = "Partly cloudy";
      else if (wmoCode <= 48)                   cond = "Fog/mist";
      else if (wmoCode <= 57)                   cond = "Drizzle";
      else if (wmoCode <= 67)                   cond = "Rain";
      else if (wmoCode <= 77)                   cond = "Snow";
      else if (wmoCode <= 82)                   cond = "Showers";
      else if (wmoCode <= 99)                   cond = "Thunderstorm";

      char buf[40];
      snprintf(buf, sizeof(buf), "%.0f%cC %s", temp, (char)247, cond);
      weatherLine = String(buf);
      weatherOk   = true;
      Serial.print("Weather: ");
      Serial.println(weatherLine);
    } else {
      Serial.println("Weather JSON parse error");
      weatherLine = "weather unavailable";
      weatherOk   = false;
    }
  } else {
    Serial.printf("Weather HTTP error: %d\n", code);
    weatherLine = "weather unavailable";
    weatherOk   = false;
  }
  http.end();
  lastWeatherFetch = millis();
}

// ── Time helper ──────────────────────────────────────────────────────────────
String buildTimeLine() {
  struct tm t;
  if (!getLocalTime(&t)) {
    return "time sync...";
  }
  char buf[20];
  strftime(buf, sizeof(buf), "%H:%M:%S", &t);
  return String(buf);
}

// ── Display refresh ──────────────────────────────────────────────────────────
void updateDisplay() {
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  if (customMessage.length() > 0) {
    // Show incoming message — wrap at word boundaries is handled by GFX
    display.setCursor(0, 0);
    display.println("-- Message --");
    display.println();
    display.setTextSize(1);
    display.println(customMessage);
  } else {
    // ── Dashboard layout ──
    // Row 0: "DESK CENTRE" header (small)
    display.setCursor(0, 0);
    display.print("DESK COMMAND CENTRE");

    // Row 1: time (large)
    display.setTextSize(2);
    display.setCursor(0, 12);
    display.print(buildTimeLine());

    // Row 2: weather (small)
    display.setTextSize(1);
    display.setCursor(0, 42);
    display.print(weatherLine);

    // Row 3: IP hint
    if (WiFi.status() == WL_CONNECTED) {
      display.setCursor(0, 54);
      display.print(WiFi.localIP().toString());
    } else {
      display.setCursor(0, 54);
      display.print("No Wi-Fi");
    }
  }

  display.display();
}

// ── Web server handlers ──────────────────────────────────────────────────────
void handleRoot() {
  String html =
    "<!DOCTYPE html><html><head>"
    "<meta name='viewport' content='width=device-width,initial-scale=1'>"
    "<title>Desk Command Centre</title>"
    "<style>body{font-family:sans-serif;max-width:400px;margin:40px auto;padding:0 16px}"
    "input[type=text]{width:100%;box-sizing:border-box;padding:8px;font-size:1rem;margin:8px 0}"
    "button{padding:10px 24px;font-size:1rem;cursor:pointer;background:#1a1a2e;color:#fff;border:none;border-radius:4px}"
    "</style></head><body>"
    "<h2>Desk Command Centre</h2>"
    "<p>Type a message to display on the OLED for a few seconds.</p>"
    "<form method='POST' action='/send'>"
    "<input type='text' name='msg' maxlength='64' placeholder='Your message' required>"
    "<br><button type='submit'>Send to OLED</button>"
    "</form>"
    "</body></html>";
  server.send(200, "text/html", html);
}

void handleSend() {
  if (server.hasArg("msg")) {
    String msg = server.arg("msg");
    msg.trim();
    if (msg.length() > 0) {
      showMessage(msg);
      server.send(200, "text/html",
        "<!DOCTYPE html><html><head>"
        "<meta http-equiv='refresh' content='2;url=/'>"
        "<meta name='viewport' content='width=device-width,initial-scale=1'>"
        "<title>Sent</title>"
        "<style>body{font-family:sans-serif;text-align:center;margin-top:80px}</style>"
        "</head><body><h2>Message sent!</h2><p>Returning…</p></body></html>");
      return;
    }
  }
  server.sendHeader("Location", "/");
  server.send(302);
}

void showMessage(const String& msg) {
  customMessage  = msg;
  msgShowUntil   = millis() + MSG_DISPLAY_MS;
  Serial.print("Displaying message: ");
  Serial.println(msg);
  updateDisplay();
}