🌦️ ESP32 FreeRTOS Weather Logger 🌡️📊

A simple ESP32 project that uses FreeRTOS to log temperature and humidity from a DHT11 sensor and display it on the Blynk IoT platform with live graphs.

A dedicated FreeRTOS task samples the sensor and pushes the latest reading into a length-1 FreeRTOS queue; the main task runs the Blynk client and uploads that reading on a timer. Keeping every Blynk call on a single task makes the cross-task hand-off thread-safe.

📌 Required Components & Software

• ESP32 (38-pin) NodeMCU Development Board
• DHT11 Temperature & Humidity Sensor
• Jumper wires + breadboard
• Arduino IDE (or arduino-cli) with:
  • the ESP32 board package (esp32 by Espressif)
  • the Blynk library
  • the DHT sensor library (Adafruit) + its Adafruit Unified Sensor dependency

🔧 Wiring Diagram

ESP32 GPIO Pin	Component
GPIO 4	DHT11 Data
3.3V	DHT11 VCC
GND	DHT11 GND

📝 Code

The full sketch lives in RTOS-Weather-Logger.ino. The core of it: a FreeRTOS task reads the DHT11 (skipping failed NaN reads) and publishes to a length-1 queue, while a BlynkTimer on the main task uploads the freshest sample.

// FreeRTOS task: sample the DHT11 and publish the latest valid reading.
void sensorTask(void *pvParameters) {
  for (;;) {
    Reading r;
    r.temperature = dht.readTemperature();   // Celsius
    r.humidity    = dht.readHumidity();

    if (isnan(r.temperature) || isnan(r.humidity)) {
      Serial.println("DHT read failed; skipping sample");
    } else {
      xQueueOverwrite(readingQueue, &r);     // keep only the freshest sample
    }
    vTaskDelay(pdMS_TO_TICKS(SAMPLE_PERIOD_MS));
  }
}

// Runs on the main (Blynk-safe) task: push the most recent sample.
void uploadReading() {
  Reading r;
  if (xQueuePeek(readingQueue, &r, 0) == pdTRUE) {
    Blynk.virtualWrite(V5, r.temperature);
    Blynk.virtualWrite(V6, r.humidity);
  }
}

void loop() {
  Blynk.run();
  timer.run();
}

🚀 How to Run

1. Install the ESP32 board package in the Arduino IDE (Boards Manager → "esp32"), plus the Blynk and DHT sensor library packages (Library Manager).

2. Open RTOS-Weather-Logger.ino and fill in your BLYNK_TEMPLATE_ID, BLYNK_TEMPLATE_NAME, BLYNK_AUTH_TOKEN, Wi-Fi ssid, and pass.

3. Select Tools → Board → ESP32 Dev Module, pick the serial port, and click Upload.

   Or from the command line with arduino-cli:

   arduino-cli compile --fqbn esp32:esp32:esp32 .
   arduino-cli upload  --fqbn esp32:esp32:esp32 -p /dev/ttyUSB0 .
   arduino-cli monitor -p /dev/ttyUSB0 -c baudrate=115200

4. In the Blynk app, add a widget bound to V5 (temperature) and another to V6 (humidity).

📽️ Demo Video

🔗 Click here to watch the demonstration on LinkedIn

🛠️ License

This project is open-source and available under the MIT License.

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✨ Happy coding with ESP32 & FreeRTOS! 🚀