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¿Cómo escuchar el cambio característico de BLE con la API web bluetooth?

Tengo una báscula BLE que pretendo usar con la API web de bluetooth. Con el escáner BLE, logré encontrar el servicio relevante y el UUID característico para la medición del peso. Con eso pude conectarme al dispositivo, pero no tengo suerte leyendo ningún valor de la característica... simplemente se desconecta después de unos segundos. ¿Qué hago mal? (configuración: android10, cromo 92.0.4515.131)

Aquí está el código de reacción:

 import { useState } from "react"; const App = () => { const [reading, setReading] = useState(null); const options = { primaryService: "0000780a-0000-1000-8000-00805f9b34fb", serviceCharacteristic: "00008aa2-0000-1000-8000-00805f9b34fb", }; function handleScaleMeasurementCharacteristic(characteristic) { console.log(characteristic); console.log("Starting notifications..."); return characteristic.startNotifications().then((char) => { console.log("Adding event listener..."); char.addEventListener( "oncharacteristicvaluechanged", onCharacteristicValueChanged ); }); } const onCharacteristicValueChanged = (event) => { setReading(event.target.value.getUint8(0)); }; const onDisconnected = (event) => { console.log(`The device ${event.target.name} is disconnected`); }; const onButtonClick = () => { navigator.bluetooth .requestDevice({ filters: [{ services: [options.primaryService] }], }) .then((device) => { device.addEventListener("gattserverdisconnected", onDisconnected); return device.gatt.connect(); }) .then((server) => server.getPrimaryService(options.primaryService)) .then((service) => { service .getCharacteristic(options.serviceCharacteristic) .then(handleScaleMeasurementCharacteristic); }); }; return ( <> <center style={{ paddingTop: 50 }}> {reading !== null ? ( <h2>{reading}</h2> ) : ( <button onClick={onButtonClick}>CONNECT TO SCALE</button> )} </center> </> ); }; export default App;

Y aquí está el registro de la consola:

captura de pantalla del registro de la consola

about 4 years ago · Juan Pablo Isaza
1 answers
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0

El tipo de evento es characteristicvaluechanged . Usando el método addEventListener:

 addEventListener('characteristicvaluechanged', event => { });

Lo mismo, pero usando la propiedad del controlador de eventos oncharacteristicvaluechanged:

 oncharacteristicvaluechanged = event => { };
about 4 years ago · Juan Pablo Isaza Report
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