basic UI dashboard
						commit
						db28d00f63
					
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{ "temperature": 24.60, "humidity": 52.68 }
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<svg xmlns="http://www.w3.org/2000/svg" width="512" height="512" viewBox="0 0 512 512"><title>ionicons-v5-f</title><path d="M400,240c-8.89-89.54-71-144-144-144-69,0-113.44,48.2-128,96C68,198,16,235.59,16,304c0,66,54,112,120,112H396c55,0,100-27.44,100-88C496,268.18,443,242.24,400,240Z" style="fill:none;stroke:white;stroke-linejoin:round;stroke-width:32px"/></svg>
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<svg xmlns='http://www.w3.org/2000/svg' width='512' height='512' viewBox='0 0 512 512'><title>ionicons-v5-q</title><line x1='256' y1='48' x2='256' y2='96' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><line x1='256' y1='416' x2='256' y2='464' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><line x1='403.08' y1='108.92' x2='369.14' y2='142.86' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><line x1='142.86' y1='369.14' x2='108.92' y2='403.08' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><line x1='464' y1='256' x2='416' y2='256' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><line x1='96' y1='256' x2='48' y2='256' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><line x1='403.08' y1='403.08' x2='369.14' y2='369.14' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><line x1='142.86' y1='142.86' x2='108.92' y2='108.92' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/><circle cx='256' cy='256' r='80' style='fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px'/></svg>
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<svg xmlns="http://www.w3.org/2000/svg" width="512" height="512" viewBox="0 0 512 512"><title>ionicons-v5-q</title><path d="M307.72,302.27a8,8,0,0,1-3.72-6.75V80a48,48,0,0,0-48-48h0a48,48,0,0,0-48,48V295.52a8,8,0,0,1-3.71,6.74,97.51,97.51,0,0,0-44.19,86.07A96,96,0,0,0,352,384,97.49,97.49,0,0,0,307.72,302.27Z" style="fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px"/><line x1="256" y1="112" x2="256" y2="384" style="fill:none;stroke:white;stroke-linecap:round;stroke-miterlimit:10;stroke-width:32px"/><circle cx="256" cy="384" r="48"/></svg>
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<svg xmlns="http://www.w3.org/2000/svg" width="512" height="512" viewBox="0 0 512 512"><title>ionicons-v5-r</title><path d="M400,320c0,88.37-55.63,144-144,144S112,408.37,112,320c0-94.83,103.23-222.85,134.89-259.88a12,12,0,0,1,18.23,0C296.77,97.15,400,225.17,400,320Z" style="fill:none;stroke:white;stroke-miterlimit:10;stroke-width:32px"/><path d="M344,328a72,72,0,0,1-72,72" style="fill:none;stroke:white;stroke-linecap:round;stroke-linejoin:round;stroke-width:32px"/></svg>
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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>Air Quality Monitor</title>
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  <link href="https://fonts.googleapis.com/css2?family=Roboto:wght@300;400&display=swap" rel="stylesheet">
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  <style>
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    /* General Styles */
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    * { margin: 0; padding: 0; box-sizing: border-box; font-family: 'Roboto', sans-serif; }
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    body { display: flex; flex-direction: column; align-items: center; justify-content: center; background: #f5f5f5; color: #333; height: 100vh; }
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    h1 { font-size: 2em; color: #444; margin-bottom: 20px; }
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    /* Container for Sensors */
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    .sensor-container {
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      display: flex;
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      flex-wrap: wrap;
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      justify-content: center;
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      gap: 20px;
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      width: 100%;
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      max-width: 800px;
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      padding: 10px;
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    }
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    /* Sensor Box */
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    .sensor {
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      background: #fff;
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      box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
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      border-radius: 10px;
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      width: 180px;
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      padding: 20px;
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      text-align: center;
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      transition: transform 0.2s ease, box-shadow 0.2s ease;
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    }
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    .sensor:hover { transform: scale(1.05); box-shadow: 0 8px 16px rgba(0, 0, 0, 0.15); }
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    /* Sensor Titles */
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    .sensor-title {
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      font-weight: 400;
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      color: #555;
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      font-size: 1.2em;
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      margin-bottom: 10px;
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      display: flex;
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      align-items: center;
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      justify-content: center;
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    }
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    /* Sensor Value */
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    .sensor-value {
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      font-size: 2.5em;
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      font-weight: 300;
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      color: #333;
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      margin-bottom: 5px;
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      animation: fadeIn 0.5s ease;
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    }
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    .unit { font-size: 0.8em; color: #777; }
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    /* Icon Styles */
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    .sensor-icon {
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      width: 30px;
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      height: 30px;
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      margin-right: 8px;
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      filter: grayscale(50%);
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    }
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    /* Keyframes for Smooth Animations */
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    @keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
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  </style>
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</head>
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<body>
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  <h1>Room Air Quality Monitor</h1>
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  <div class="sensor-container">
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    <div id="temperature" class="sensor">
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      <div class="sensor-title">
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        <img src="./images/thermometer-outline.svg" class="sensor-icon" alt="Temperature Icon">
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        Temperature
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      </div>
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      <div class="sensor-value" id="temp-value">--</div>
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      <div class="unit">℃</div>
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    </div>
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    <div id="humidity" class="sensor">
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      <div class="sensor-title">
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        <img src="./images/water-outline.svg" class="sensor-icon" alt="Humidity Icon">
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        Humidity
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      </div>
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      <div class="sensor-value" id="humidity-value">--</div>
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      <div class="unit">%</div>
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    </div>
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    <div id="co2" class="sensor">
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      <div class="sensor-title">
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        <img src="./images/cloud-outline.svg" class="sensor-icon" alt="CO2 Icon">
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        CO₂
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      </div>
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      <div class="sensor-value" id="co2-value">--</div>
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      <div class="unit">ppm</div>
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    </div>
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    <div id="pressure" class="sensor">
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      <div class="sensor-title">
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        <img src="./images/sunny-outline.svg" class="sensor-icon" alt="Pressure Icon">
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        Pressure
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      </div>
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      <div class="sensor-value" id="pressure-value">--</div>
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      <div class="unit">hPa</div>
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    </div>
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  </div>
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  <script>
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    async function fetchData() {
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      try {
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        const res = await Promise.all([
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          //fetch("./data/BH1750.json"),
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          //fetch("./data/BMP180.json"),
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          fetch("./data/HTU21D.json"),
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          //fetch("./data/MH_Z19.json")
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        ]);
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        const data = (await Promise.all(res.map(r => r.json()))).reduce((acc, item) => ({ ...acc, ...item }), {});
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        return data;
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      } catch (error) {
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        console.error("Failed to fetch sensor data:", error);
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        return {};
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      }
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    }
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    function updateUI(data) {
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      document.getElementById("temp-value").textContent = data.temperature ? data.temperature.toFixed(1) : "--";
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      document.getElementById("humidity-value").textContent = data.humidity ? data.humidity.toFixed(1) : "--";
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      document.getElementById("co2-value").textContent = data.co2 ? data.co2 : "--";
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      document.getElementById("pressure-value").textContent = data.pressure ? data.pressure.toFixed(1) : "--";
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    }
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    async function refreshData() {
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      const data = await fetchData();
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      updateUI(data);
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    }
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    setInterval(refreshData, 6000); // Refresh every 60 seconds
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    refreshData(); // Initial fetch
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  </script>
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</body>
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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>Simple Sensor Dashboard</title>
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  <style>
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    body { font-family: Arial, sans-serif; text-align: center; }
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    .sensor { margin: 10px; padding: 10px; border: 1px solid #ccc; }
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    .sensor-title { font-weight: bold; }
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    .sensor-value { font-size: 2em; color: #333; }
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  </style>
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</head>
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<body>
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  <h1>Sensor Data</h1>
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  <div id="temperature" class="sensor">
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    <div class="sensor-title">Temperature</div>
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    <div class="sensor-value" id="temp-value">--</div>
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  </div>
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  <div id="humidity" class="sensor">
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    <div class="sensor-title">Humidity</div>
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    <div class="sensor-value" id="humidity-value">--</div>
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  </div>
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  <script>
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    async function fetchData() {
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      try {
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        const tempResponse = await fetch('./data/HTU21D.json');
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        const tempData = await tempResponse.json();
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        document.getElementById('temp-value').textContent = tempData.temperature.toFixed(1) + ' ℃';
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        document.getElementById('humidity-value').textContent = tempData.humidity.toFixed(1) + ' %';
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      } catch (error) {
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        console.error('Error fetching data:', error);
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      }
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    }
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    // Update data every 60 seconds
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    setInterval(fetchData, 60000);
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    fetchData(); // Initial fetch
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  </script>
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</body>
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</html>
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CC=gcc
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CFLAGS=-I.
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DEPS =
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OBJ = main.o htu21d.o
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EXTRA_LIBS=-li2c
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%.o: %.c $(DEPS)
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	$(CC) -c -o $@ $< $(CFLAGS)
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HTU21D: $(OBJ)
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	$(CC) -o $@ $^ $(CFLAGS) $(EXTRA_LIBS)
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.PHONY: clean
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clean:
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	rm -f HTU21D $(OBJ)
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# Introduction
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This repository guides you to implement and use the HTU21D temperature and humidity sensor by using I2C communication. The repository contains the following files:
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- `htu21d.h` library header files
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- `htu21d.c` implemenation methods file
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- `main.c` an example file to test I2C communication using the library `htu21d`
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- `example` output file precompiled in a raspberry pi zero that returns temperature and humidity
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# Setup the raspberry
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## Enable I2C on the Raspberry Pi:
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- Run sudo raspi-config.
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- Navigate to Interfacing Options → I2C and enable it.
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- Reboot the Pi.
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## Install I2C Tools and Development Libraries: 
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```
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sudo apt-get update
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sudo apt-get install i2c-tools libi2c-dev
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```
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## Check if the sensor is detected:
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```
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sudo i2cdetect -y 1
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```
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This command should show an address for the HTU21D, typically 0x40.
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```
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     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
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00:                         -- -- -- -- -- -- -- --
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10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
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70: -- -- -- -- -- -- -- --
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```
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# My own header files for HTU21D sensor
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This is a detailed guide to configure and create your own files to comunicate with each sensor used by the air-quality sensor.
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## Header 
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Create the Header File `htu21d.h` with Header Guard and Includes:
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```c
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#ifndef HTU21D_H
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#define HTU21D_H
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// I2C Address
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#define HTU21D_I2C_ADDR 0x40
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// Commands
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#define HTU21D_TEMP 0xE3
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#define HTU21D_HUMID 0xE5
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#define HTU21D_RESET 0xFE
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// Function declarations:
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// Temp
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int getTemperature(int fd, double *temperature);
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// Humidity
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int getHumidity(int fd, double *humidity);
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#endif // HTU21D_H
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```
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##  Implement the Sensor Communication `htu21d.c`
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```c
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#include <unistd.h> //to send commands to and receive from I2C device
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#include <sys/ioctl.h>//setting up and controlling the I2C device settings
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#include <linux/i2c-dev.h>//definitions for system calls and structures specific to I2C
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#include <i2c/smbus.h>//SMBus commands in a more standardized way for I2C
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#include <stdio.h>//perror
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#include "htu21d.h" // my own header file
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// Reset function:
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int reset(int fd)
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		||||
{
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        if(0 > ioctl(fd, I2C_SLAVE, HTU21D_I2C_ADDR))
 | 
			
		||||
        {
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		||||
                perror("Failed to open the bus");
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		||||
                return -1;
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		||||
        }
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		||||
        i2c_smbus_write_byte(fd, HTU21D_RESET);
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		||||
        return 0;
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		||||
}
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		||||
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		||||
// Get temperature:
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		||||
int getTemperature(int fd, double *temperature)
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		||||
{
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		||||
        reset(fd);
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		||||
        char buf[3];
 | 
			
		||||
        __s32 res = i2c_smbus_read_i2c_block_data(fd, HTU21D_TEMP,3,buf);
 | 
			
		||||
        if(res<0)
 | 
			
		||||
        {
 | 
			
		||||
                perror("Failed to read from the device");
 | 
			
		||||
                return -1;
 | 
			
		||||
        }
 | 
			
		||||
        *temperature = -46.85 + 175.72 * (buf[0]*256 + buf[1]) / 65536.0;
 | 
			
		||||
        return 0;
 | 
			
		||||
}
 | 
			
		||||
 | 
			
		||||
 | 
			
		||||
// Get humidity:
 | 
			
		||||
int getHumidity(int fd, double *humidity)
 | 
			
		||||
{
 | 
			
		||||
        reset(fd);
 | 
			
		||||
        char buf[3];
 | 
			
		||||
        __s32 res = i2c_smbus_read_i2c_block_data(fd, HTU21D_HUMID, 3, buf);
 | 
			
		||||
        if(res<0)
 | 
			
		||||
        {
 | 
			
		||||
                perror("Failed to read from the device");
 | 
			
		||||
                return -1;
 | 
			
		||||
        }
 | 
			
		||||
        *humidity = -6 + 125 * (buf[0]*256 + buf[1]) / 65536.0;
 | 
			
		||||
        return 0;
 | 
			
		||||
}
 | 
			
		||||
```
 | 
			
		||||
 | 
			
		||||
 | 
			
		||||
### Using the library
 | 
			
		||||
 | 
			
		||||
```c
 | 
			
		||||
#include <stdio.h>
 | 
			
		||||
#include <errno.h>
 | 
			
		||||
#include <stdlib.h>
 | 
			
		||||
#include <string.h>
 | 
			
		||||
#include <fcntl.h>
 | 
			
		||||
 | 
			
		||||
#include "htu21d.h"
 | 
			
		||||
 | 
			
		||||
int main()
 | 
			
		||||
{
 | 
			
		||||
        char filename[20];
 | 
			
		||||
        snprintf(filename, 19, "/dev/i2c-%d", 1);
 | 
			
		||||
        int fd = open(filename, O_RDWR);
 | 
			
		||||
        if (0 > fd)
 | 
			
		||||
        {
 | 
			
		||||
                fprintf(stderr, "ERROR: Unable to access HTU21D sensor module: %s\n", strerror (errno));
 | 
			
		||||
                exit(-1);
 | 
			
		||||
        }
 | 
			
		||||
        // Retrieve temperature and humidity
 | 
			
		||||
        double temperature = 0;
 | 
			
		||||
        double humidity = 0;
 | 
			
		||||
        if ( (0 > getHumidity(fd, &humidity)) || (0 > getTemperature(fd, &temperature)) )
 | 
			
		||||
        {
 | 
			
		||||
                fprintf(stderr, "ERROR: HTU21D sensor module not found\n");
 | 
			
		||||
                exit(-1);
 | 
			
		||||
        }
 | 
			
		||||
 | 
			
		||||
        // Print temperature and humidity on the screen
 | 
			
		||||
        printf("HTU21D Sensor Module\n");
 | 
			
		||||
        printf("%5.2fC\n", temperature);
 | 
			
		||||
        printf("%5.2f%%rh\n", humidity);
 | 
			
		||||
 | 
			
		||||
        return 0;
 | 
			
		||||
}
 | 
			
		||||
```
 | 
			
		||||
 | 
			
		||||
# Compiling and testing 
 | 
			
		||||
Then to properly compile whitout a make file:
 | 
			
		||||
```sh
 | 
			
		||||
gcc -o example main.c htu21d.c -li2c
 | 
			
		||||
```
 | 
			
		||||
or 
 | 
			
		||||
```sh
 | 
			
		||||
gcc -o example main.c htu21d.c -I. -li2c
 | 
			
		||||
```
 | 
			
		||||
 | 
			
		||||
### Wiring htu21d to Rasp-zero
 | 
			
		||||
Htu -> Rasp-Zero
 | 
			
		||||
VIN -> GPIO 1
 | 
			
		||||
GND -> GPIO 9 or (6)
 | 
			
		||||
SCL -> GPIO 5
 | 
			
		||||
SDA -> GPIO 3
 | 
			
		||||
 | 
			
		||||

 | 
			
		||||
@ -0,0 +1,52 @@
 | 
			
		||||
#include <unistd.h> //to send commands to and receive from I2C device
 | 
			
		||||
#include <sys/ioctl.h>//setting up and controlling the I2C device settings
 | 
			
		||||
#include <linux/i2c-dev.h>//definitions for system calls and structures specific to I2C
 | 
			
		||||
#include <i2c/smbus.h>//SMBus commands in a more standardized way for I2C
 | 
			
		||||
#include <stdio.h>//perror
 | 
			
		||||
 | 
			
		||||
#include "htu21d.h" // my own header file
 | 
			
		||||
 | 
			
		||||
// Reset function:
 | 
			
		||||
int reset(int fd)
 | 
			
		||||
{
 | 
			
		||||
	if(0 > ioctl(fd, I2C_SLAVE, HTU21D_I2C_ADDR))
 | 
			
		||||
	{
 | 
			
		||||
		perror("Failed to open the bus");
 | 
			
		||||
		return -1;
 | 
			
		||||
	}
 | 
			
		||||
	i2c_smbus_write_byte(fd, HTU21D_RESET);
 | 
			
		||||
	return 0;
 | 
			
		||||
}
 | 
			
		||||
 | 
			
		||||
// Get temperature:
 | 
			
		||||
int getTemperature(int fd, double *temperature)
 | 
			
		||||
{
 | 
			
		||||
	reset(fd);
 | 
			
		||||
	char buf[3];
 | 
			
		||||
	__s32 res = i2c_smbus_read_i2c_block_data(fd, HTU21D_TEMP,3,buf);
 | 
			
		||||
	if(res<0)
 | 
			
		||||
	{
 | 
			
		||||
		perror("Failed to read from the device");
 | 
			
		||||
		return -1;
 | 
			
		||||
	}
 | 
			
		||||
	*temperature = -46.85 + 175.72 * (buf[0]*256 + buf[1]) / 65536.0;
 | 
			
		||||
	return 0;
 | 
			
		||||
}
 | 
			
		||||
 | 
			
		||||
 | 
			
		||||
// Get humidity:
 | 
			
		||||
int getHumidity(int fd, double *humidity)
 | 
			
		||||
{
 | 
			
		||||
	reset(fd);
 | 
			
		||||
	char buf[3];
 | 
			
		||||
	__s32 res = i2c_smbus_read_i2c_block_data(fd, HTU21D_HUMID, 3, buf);
 | 
			
		||||
	if(res<0)
 | 
			
		||||
	{
 | 
			
		||||
		perror("Failed to read from the device");
 | 
			
		||||
		return -1;
 | 
			
		||||
	}
 | 
			
		||||
	*humidity = -6 + 125 * (buf[0]*256 + buf[1]) / 65536.0;
 | 
			
		||||
	return 0;
 | 
			
		||||
}
 | 
			
		||||
 | 
			
		||||
 | 
			
		||||
@ -0,0 +1,19 @@
 | 
			
		||||
#ifndef HTU21D_H
 | 
			
		||||
#define HTU21D_H
 | 
			
		||||
 | 
			
		||||
// I2C Address
 | 
			
		||||
#define HTU21D_I2C_ADDR 0x40
 | 
			
		||||
// Commands
 | 
			
		||||
#define HTU21D_TEMP 0xE3
 | 
			
		||||
#define HTU21D_HUMID 0xE5
 | 
			
		||||
#define HTU21D_RESET 0xFE
 | 
			
		||||
 | 
			
		||||
 | 
			
		||||
// Function declarations:
 | 
			
		||||
 | 
			
		||||
// Temp
 | 
			
		||||
int getTemperature(int fd, double *temperature);
 | 
			
		||||
// Humidity
 | 
			
		||||
int getHumidity(int fd, double *humidity);
 | 
			
		||||
 | 
			
		||||
#endif // HTU21D_H
 | 
			
		||||
											
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								@ -0,0 +1,39 @@
 | 
			
		||||
#include <stdio.h>
 | 
			
		||||
#include <errno.h>
 | 
			
		||||
#include <stdlib.h>
 | 
			
		||||
#include <string.h>
 | 
			
		||||
#include <fcntl.h>
 | 
			
		||||
 | 
			
		||||
#include "htu21d.h"
 | 
			
		||||
 | 
			
		||||
int main()
 | 
			
		||||
{
 | 
			
		||||
        char filename[20];
 | 
			
		||||
        snprintf(filename, 19, "/dev/i2c-%d", 2);
 | 
			
		||||
        int fd = open(filename, O_RDWR);
 | 
			
		||||
        if (0 > fd)
 | 
			
		||||
        {
 | 
			
		||||
                fprintf(stderr, "ERROR: Unable to access HTU21D sensor module: %s\n", strerror (errno));
 | 
			
		||||
                exit(-1);
 | 
			
		||||
        }
 | 
			
		||||
 | 
			
		||||
        // Retrieve temperature and humidity
 | 
			
		||||
        double temperature = 0;
 | 
			
		||||
        double humidity = 0;
 | 
			
		||||
        if ( (0 > getHumidity(fd, &humidity)) || (0 > getTemperature(fd, &temperature)) )
 | 
			
		||||
        {
 | 
			
		||||
                fprintf(stderr, "ERROR: HTU21D sensor module not found\n");
 | 
			
		||||
                exit(-1);
 | 
			
		||||
        }
 | 
			
		||||
 | 
			
		||||
        // Print temperature and humidity on the screen
 | 
			
		||||
        printf("{ ");
 | 
			
		||||
        printf("\"temperature\": %5.2f, ", temperature);
 | 
			
		||||
        printf("\"humidity\": %5.2f ", humidity);
 | 
			
		||||
        printf("}");
 | 
			
		||||
        //printf("HTU21D Sensor Module\n");
 | 
			
		||||
        //printf("%5.2fC\n", temperature);
 | 
			
		||||
        //printf("%5.2f%%rh\n", humidity);
 | 
			
		||||
 | 
			
		||||
        return 0;
 | 
			
		||||
}
 | 
			
		||||
											
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