Web Bluetooth / Get Characteristics (Async Await) Sample

Available in Chrome 55+ | View on GitHub | Browse Samples

The Web Bluetooth API lets websites discover and communicate with devices over the Bluetooth 4 wireless standard using the Generic Attribute Profile (GATT). It is currently partially implemented in Android M, Chrome OS, Mac, and Windows 10.

This sample illustrates the use of the Web Bluetooth API to get all characteristics of an advertised service from a nearby Bluetooth Low Energy Device. You may want to try this demo with the BLE Peripheral Simulator App from the Google Play Store and check out the Get Characteristics (Promises) sample.

Live Output











  
    
      
    
  

  
    
JavaScript Snippet

  

  
    
async function onButtonClick() {
  let serviceUuid = document.querySelector('#service').value;
  if (serviceUuid.startsWith('0x')) {
    serviceUuid = parseInt(serviceUuid);
  }

  let characteristicUuid = document.querySelector('#characteristic').value;
  if (characteristicUuid.startsWith('0x')) {
    characteristicUuid = parseInt(characteristicUuid);
  }

  try {
    log('Requesting Bluetooth Device...');
    const device = await navigator.bluetooth.requestDevice({
        filters: [{services: [serviceUuid]}]});
  
    log('Connecting to GATT Server...');
    const server = await device.gatt.connect();

    log('Getting Service...');
    const service = await server.getPrimaryService(serviceUuid);

    log('Getting Characteristics...');
    let characteristics;
    if (characteristicUuid) {
      characteristics = await service.getCharacteristics(characteristicUuid);
    } else {
      characteristics = await service.getCharacteristics();
    }

    log('> Characteristics: ' +
      characteristics.map(c => c.uuid).join('\n' + ' '.repeat(19)));
  } catch(error) {
    log('Argh! ' + error);
  }
}