webbluetooth/examples/heartrate.js

Node.js implementation of the Web Bluetooth Specification

/*
* Node Web Bluetooth
* Copyright (c) 2017 Rob Moran
*
* The MIT License (MIT)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/

const bluetooth = require("../").bluetooth;

(async () => {
	try {
		console.log("Requesting Bluetooth Devices...");

		const device = await bluetooth.requestDevice({
			filters: [{ services: [ "heart_rate" ] }]
		});
		console.log(`Found device: ${device.name}`);

		const server = await device.gatt.connect();
		console.log(`Gatt server connected: ${server.connected}`);
		
		const service = await server.getPrimaryService("heart_rate");
		console.log(`Primary service: ${service.uuid}`);

		const characteristic = await service.getCharacteristic("heart_rate_measurement");
		console.log(`Characteristic: ${characteristic.uuid}`);

		await characteristic.startNotifications();
		console.log("Notifications started");

		characteristic.addEventListener("characteristicvaluechanged", event => {
			if (event.value.buffer.byteLength) console.log(event.value.getUint16(0));
		});
	} catch(error) {
		console.log(error);
		process.exit(1);
	};
})();