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# Air Quality Monitor
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**Air Quality Monitor** is a lightweight web interface that displays real-time data from two environmental sensors: **HTU21D** and **BMP180**. The system uses **NGINX** to serve an HTML page that reads live data from JSON files.
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## Project Description
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This project was designed to visualize environmental parameters in a simple, fast, and efficient way using an embedded graphical interface. The data is obtained from the following sensors:
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- **HTU21D**: Temperature and relative humidity.
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- **BMP180**: Atmospheric pressure and temperature.
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The data is stored in two JSON files, updated by the embedded system and displayed through an HTML/JavaScript-based frontend.
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---
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## Project Structure
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air-quality-monitor/
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│
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├── BMP180.json # Pressure and temperature data from BMP180
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├── HTU21D.json # Temperature and humidity data from HTU21D
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├── index.html # Main web interface
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├── index.js # JavaScript logic to fetch and display JSON data
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├── style.css # Custom CSS styles
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> The `.json` files are automatically updated by C programs that communicate with the sensors via I2C.
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---
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## 🚀 Installation & Deployment with NGINX
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### Requirements
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- Linux server with `nginx` installed.
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- Root access or permission to modify NGINX configuration.
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### Steps
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1. Install NGINX (if not already installed):
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```bash
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sudo apt update
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sudo apt install nginx
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```
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2. Copy the project files to NGINX’s public directory (e.g., /var/www/html):
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``` bash
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```
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3. Redirect the configuration file to our repository folder:
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```bash
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sudo vi /etc/nginx/sites-available/default
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```
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4. Replace the line:
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```bash
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root /var/www/html;
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```
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with:
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```bash
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root /home/debian/path/to/your/repository;
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```
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5. Apply chages with:
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```bash
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sudo systemctl restart nginx
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```
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## User interface
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This is a simple web page that displays real-time sensor data from two devices:
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• BMP180: Shows temperature and pressure.
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• HTU21D: Shows humidity and temperature.
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It’s styled with a separate CSS file (style.css) and fetches live data using JavaScript (index.js), which likely reads values from two JSON files (BMP180.json and HTU21D.json).
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### HTML
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#### Complete code
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```html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8" />
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<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
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<title>Sensor Dashboard</title>
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<link rel="stylesheet" href="style.css" />
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</head>
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<body>
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<div class="background"></div>
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<div class="container">
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<h1>Sensor Dashboard</h1>
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<div class="sensor-card">
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<img src="https://cdn-icons-png.flaticon.com/512/1126/1126741.png" alt="Temperature & Pressure Icon">
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<h2>BMP180</h2>
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<div class="data">
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<span id="temperature">Temperature: -- °C</span>
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<span id="pressure">Pressure: -- hPa</span>
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</div>
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</div>
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<div class="sensor-card">
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<img src="https://cdn-icons-png.flaticon.com/512/728/728093.png" alt="Humidity Icon">
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<h2>HTU21D</h2>
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<div class="data">
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<span id="humidity">Humidity: -- %</span>
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<span id="tempHTU">Temperature: -- °C</span>
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</div>
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</div>
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</div>
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<script src="index.js"></script>
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</body>
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</html>
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```
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#### Explanation
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```html
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<!DOCTYPE html>
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<html lang="en">
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```
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• Declares this document as HTML5.
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• lang="en" sets the document language to English, which is useful for accessibility and SEO.
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##### HEAD
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```html
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<head>
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<meta charset="UTF-8" />
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<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
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<title>Sensor Dashboard</title>
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<link rel="stylesheet" href="style.css" />
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</head>
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```
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• charset="UTF-8" ensures proper text encoding.
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• viewport makes the layout responsive on mobile devices.
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• title is what appears in the browser tab.
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• link imports the external CSS file (style.css) for styling.
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##### BODY
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```html
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<body>
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<div class="background"></div>
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<div class="container">
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...
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</div>
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<script src="index.js"></script>
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</body>
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```
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• The background div might be used for a visual effect like a background image or color gradient (defined in your CSS).
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• container holds the main content (dashboard).
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• index.js is loaded at the end to ensure the DOM is ready before scripts run.
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##### Dashboard Title
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```html
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<h1>Sensor Dashboard</h1>
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```
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• This is the main heading of your web page.
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##### Sensor Card: BMP180
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```hmtl
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<div class="sensor-card">
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<img src="https://cdn-icons-png.flaticon.com/512/1126/1126741.png" alt="Temperature & Pressure Icon">
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<h2>BMP180</h2>
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<div class="data">
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<span id="temperature">Temperature: -- °C</span>
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<span id="pressure">Pressure: -- hPa</span>
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</div>
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</div>
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```
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• This block represents the BMP180 sensor.
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• The icon (from flaticon.com) visually represents pressure/temperature.
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• The id attributes (temperature, pressure) are hooks used by JavaScript to insert real values from BMP180.json.
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##### Sensor Card: HTU21D
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```html
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<div class="sensor-card">
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<img src="https://cdn-icons-png.flaticon.com/512/728/728093.png" alt="Humidity Icon">
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<h2>HTU21D</h2>
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<div class="data">
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<span id="humidity">Humidity: -- %</span>
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<span id="tempHTU">Temperature: -- °C</span>
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</div>
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</div>
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```
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• This block represents the HTU21D sensor.
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• The image is a humidity icon.
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• The id attributes (humidity, tempHTU) are also updated by JavaScript using HTU21D.json.
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##### JavaScript Integration
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```hmtl
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<script src="index.js"></script>
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```
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• This line loads your script, which is responsible for:
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• Fetching the JSON files.
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• Parsing their content.
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• Replacing the placeholder values (-- °C, -- hPa, etc.) with live sensor data.
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### Index.js
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The script fetches data from two local JSON files:
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• BMP180.json — contains temperature and pressure.
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• HTU21D.json — contains temperature and humidity.
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Then it updates the HTML every 3 seconds so the page always shows live sensor values.
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#### Full code
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```js
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function updateBMP180() {
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fetch('BMP180.json')
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.then(res => res.json())
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.then(data => {
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document.getElementById('temperature').textContent = `Temperature: ${data.temperature.toFixed(2)} °C`;
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document.getElementById('pressure').textContent = `Pressure: ${data.pressure.toFixed(2)} hPa`;
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})
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.catch(err => console.error("Error BMP180:", err));
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}
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function updateHTU21D() {
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fetch('HTU21D.json')
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.then(res => res.json())
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.then(data => {
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document.getElementById('humidity').textContent = `Humidity: ${data.humidity.toFixed(1)} %`;
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document.getElementById('tempHTU').textContent = `Temperature: ${data.temperature.toFixed(1)} °C`;
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})
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.catch(err => console.error("Error HTU21D:", err));
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}
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setInterval(() => {
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updateBMP180();
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updateHTU21D();
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}, 3000);
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// Carga inicial
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updateBMP180();
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updateHTU21D();
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```
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### Code explanation
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#### Function: updateBMP180
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```js
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function updateBMP180() {
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fetch('BMP180.json')
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.then(res => res.json())
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.then(data => {
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document.getElementById('temperature').textContent = `Temperature: ${data.temperature.toFixed(2)} °C`;
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document.getElementById('pressure').textContent = `Pressure: ${data.pressure.toFixed(2)} hPa`;
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})
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.catch(err => console.error("Error BMP180:", err));
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}
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```
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- This defines a new function named updateBMP180. You’ll call this function when you want to update the BMP180 sensor data on the page.
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- fetch('BMP180.json'): Loads the JSON file from the same directory.
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- .then(res =\>json()): Parses the response as JSON
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- .then(data +\> {}): Accesses the data inside the file.
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- document.getElementById(...) updates the corresponding <span> elements in your HTML.
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#### Function: updateHTU21D
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```js
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function updateHTU21D() {
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fetch('HTU21D.json')
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.then(res => res.json())
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.then(data => {
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document.getElementById('humidity').textContent = `Humidity: ${data.humidity.toFixed(1)} %`;
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document.getElementById('tempHTU').textContent = `Temperature: ${data.temperature.toFixed(1)} °C`;
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})
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.catch(err => console.error("Error HTU21D:", err));
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}
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```
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Works the same way as updateBMP180(), but:
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- Fetches from HTU21D.json.
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- Displays humidity and temperature.
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- Uses .toFixed(1) for 1 decimal place (common for humidity values).
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#### Auto-update every 3 seconds
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```js
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setInterval(() => {
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updateBMP180();
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updateHTU21D();
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}, 3000);
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```
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- Calls both update functions every 3,000 milliseconds (3 seconds).
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- Keeps the UI in sync with new sensor readings, assuming the .json files are being updated continuously.
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#### Initial load
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```js
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updateBMP180();
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updateHTU21D();
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```
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- Ensures the data is shown immediately on page load, before the 3-second interval kicks in.
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### CSS
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#### Full code
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```css
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* {
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margin: 0;
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padding: 0;
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box-sizing: border-box;
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font-family: "Segoe UI", sans-serif;
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}
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body, html {
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height: 100%;
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background-color: #0d1117;
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color: #ffffff;
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position: relative;
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overflow: hidden;
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}
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.background {
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background-image: url('https://wallpapers.com/images/hd/blue-circuit-board-traces-zn0xezd4t8axj9r6.webp');
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background-size: cover;
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background-position: center;
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opacity: 0.1;
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filter: blur(3px);
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position: absolute;
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top: 0; left: 0;
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width: 100%;
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height: 100%;
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z-index: -1;
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}
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.container {
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max-width: 800px;
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margin: 40px auto;
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background-color: #161b22;
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padding: 30px;
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border-radius: 20px;
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box-shadow: 0 0 30px rgba(0, 255, 255, 0.2);
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animation: fadeIn 1s ease-in;
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}
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h1 {
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text-align: center;
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margin-bottom: 30px;
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font-size: 2.5rem;
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color: #58a6ff;
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}
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.sensor-card {
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background-color: #1f2937;
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padding: 20px;
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border-radius: 15px;
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margin-bottom: 20px;
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box-shadow: 0 0 20px rgba(100, 255, 255, 0.1);
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animation: slideIn 1s ease;
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display: flex;
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flex-direction: column;
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align-items: center;
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text-align: center;
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}
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.sensor-card img {
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width: 64px;
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height: 64px;
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margin-bottom: 10px;
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}
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.sensor-card h2 {
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margin-bottom: 10px;
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color: #90cdf4;
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}
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.data span {
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display: block;
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margin: 5px 0;
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font-size: 1.2rem;
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color: #ffffff;
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}
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@keyframes fadeIn {
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from { opacity: 0; transform: translateY(-20px); }
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to { opacity: 1; transform: translateY(0); }
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}
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@keyframes slideIn {
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from { opacity: 0; transform: scale(0.9); }
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to { opacity: 1; transform: scale(1); }
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}
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```
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#### Explaining
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Global Styling
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- *: Resets default browser spacing (margin, padding) and sets a consistent font and box model across the entire page.
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- body, html:
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- Sets full height layout.
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- Applies a dark background (#0d1117) with white text.
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- Hides overflow and enables positioning for internal layers.
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⸻
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Background Layer
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- .background:
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- Adds a faint, blurred circuit board image as the background.
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- Uses opacity: 0.1 and filter: blur(3px) to give it a soft tech feel.
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- Positioned absolutely behind everything (z-index: -1).
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⸻
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Main Container
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- .container:
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- A centered, card-like section with:
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- A dark background (#161b22)
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- Rounded corners and soft glowing shadow.
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- Padding and a fade-in animation on load.
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⸻
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Title
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- h1:
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- Large, centered header in light blue (#58a6ff).
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- Styled to stand out at the top of the dashboard.
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⸻
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Sensor Cards
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- .sensor-card:
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- Styled boxes for each sensor.
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- Darker background (#1f2937) with a soft shadow.
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- Rounded corners, padding, and a slide-in animation when they load.
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- Contents are centered vertically and horizontally.
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- .sensor-card img:
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- Sensor icons sized to 64×64 pixels with margin for spacing.
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- .sensor-card h2:
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- Sub-headers for each sensor card in a soft blue (#90cdf4).
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⸻
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Data Text
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- .data span:
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- Each line of sensor data (e.g., temperature, humidity).
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- Displayed as blocks with spacing and larger font for visibility.
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⸻
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Animations
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- @keyframes fadeIn:
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- Smooth slide-down + fade-in for the container.
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- @keyframes slideIn:
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- Subtle zoom-in effect for each sensor card.
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## Sensor library
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### HTU21D library
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The library contains 3 files, HTU21D.c, htu21d.h and main.c
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#### htu21d.h
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```h
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#ifndef HTU21D_H
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#define HTU21D_H
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// HTU21D i2c address
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#define HTU21D_ADDR 0x40
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//commands for readings
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#define HTU21D_TEMP 0xE3
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#define HTU21D_HUM 0xE5
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#define HTU21D_RESET 0xFE
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//funtion declarations
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//Temp:
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int getTemp(int fd, double *temp);
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//HUM
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int getHum(int fd, double *hum);
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//RESET
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int getReset(int fd);
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#endif
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```
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- HTU21D_ADDR: The I2C address of the sensor (0x40).
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- HTU21D_TEMP: Command to read temperature (0xE3).
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- HTU21D_HUM: Command to read humidity (0xE5).
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- HTU21D_RESET: Command to reset the sensor (0xFE).
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- Declares three functions:
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1. getTemp() – for reading temperature,
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2. getHum() – for reading humidity,
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3. getReset() – for resetting the sensor.
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