webbluetooth-hrm-pro-plus/index.html at main · janposselt/webbluetooth-hrm-pro-plus · GitHub

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<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Live Heart Rate</title>
    <script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
</head>

<body>
    <h2>Live Heart Rate Dashboard</h2>
    <button onclick="connectToHeartRateMonitor()">Connect</button>
    <p id="heartRateDisplay">Heart Rate: -- BPM</p>
    <p id="batteryDisplay">Battery: --%</p>
    <canvas id="heartRateChart"></canvas>

    <script>
        let chart;
        let heartRateData = [];
        let timeLabels = [];

        async function getBatteryLevel(server) {
            try {
                const service = await server.getPrimaryService('battery_service');
                const characteristic = await service.getCharacteristic('battery_level');
                const value = await characteristic.readValue();
                const batteryLevel = value.getUint8(0);
                document.getElementById('batteryDisplay').innerText = `Battery: ${batteryLevel}%`;
            } catch (error) {
                console.error("Error reading battery:", error);
            }
        }

        async function connectToHeartRateMonitor() {
            try {
                const device = await navigator.bluetooth.requestDevice({
                    filters: [{ services: ['heart_rate'] }],
                    optionalServices: ['battery_service']
                });

                const server = await device.gatt.connect();
                const service = await server.getPrimaryService('heart_rate');
                const characteristic = await service.getCharacteristic('heart_rate_measurement');

                characteristic.addEventListener('characteristicvaluechanged', handleHeartRateMeasurement);
                await characteristic.startNotifications();
                getBatteryLevel(server);
            } catch (error) {
                console.error("Connection error:", error);
            }
        }

        function handleHeartRateMeasurement(event) {
            const value = event.target.value;
            const heartRate = parseHeartRate(value);
            document.getElementById('heartRateDisplay').innerText = `Heart Rate: ${heartRate} BPM`;

            const now = new Date().toLocaleTimeString();
            heartRateData.push(heartRate);
            timeLabels.push(now);

            if (heartRateData.length > 20) {
                heartRateData.shift();
                timeLabels.shift();
            }

            chart.update();
        }

        function parseHeartRate(value) {
            let data = new DataView(value.buffer);
            let flags = data.getUint8(0);
            let rate16Bits = flags & 0x1;
            return rate16Bits ? data.getUint16(1, true) : data.getUint8(1);
        }

        document.addEventListener("DOMContentLoaded", function () {
            let ctx = document.getElementById('heartRateChart').getContext('2d');
            chart = new Chart(ctx, {
                type: 'line',
                data: {
                    labels: timeLabels,
                    datasets: [{
                        label: 'Heart Rate (BPM)',
                        data: heartRateData,
                        borderColor: 'red',
                        backgroundColor: 'rgba(255, 0, 0, 0.2)',
                        fill: true
                    }]
                },
                options: {
                    responsive: true,
                    animation: false,
                    scales: {
                        x: { title: { display: true, text: 'Time' } },
                        y: { title: { display: true, text: 'BPM' }, min: 40, max: 200 }
                    }
                }
            });
        });
    </script>
</body>

</html>