how to receive data from bluetooth device using node.js

Question

I am new to javascript and node.js. Currently am working in medical project. First i will explain my work. I have to receive data from Bluetooth device (normal BP rate ,pulse ra

Answer 1

You can use node-ble a Node.JS library that leverages on D-Bus and avoids C++ bindings. https://github.com/chrvadala/node-ble

Here a basic example

async function main () {
  const { bluetooth, destroy } = createBluetooth()

  // get bluetooth adapter
  const adapter = await bluetooth.defaultAdapter()
  await adapter.startDiscovery()
  console.log('discovering')

  // get device and connect
  const device = await adapter.waitDevice(TEST_DEVICE)
  console.log('got device', await device.getAddress(), await device.getName())
  await device.connect()
  console.log('connected')

  const gattServer = await device.gatt()

  // read write characteristic
  const service1 = await gattServer.getPrimaryService(TEST_SERVICE)
  const characteristic1 = await service1.getCharacteristic(TEST_CHARACTERISTIC)
  await characteristic1.writeValue(Buffer.from('Hello world'))
  const buffer = await characteristic1.readValue()
  console.log('read', buffer, buffer.toString())

  // subscribe characteristic
  const service2 = await gattServer.getPrimaryService(TEST_NOTIFY_SERVICE)
  const characteristic2 = await service2.getCharacteristic(TEST_NOTIFY_CHARACTERISTIC)
  await characteristic2.startNotifications()
  await new Promise(done => {
    characteristic2.once('valuechanged', buffer => {
      console.log('subscription', buffer)
      done()
    })
  })

  await characteristic2.stopNotifications()
  destroy()
}

Answer 2

Try noble library. That's how I get information about my Xiaomi Mi Band 3 device:

const arrayBufferToHex = require('array-buffer-to-hex')
const noble = require('noble')

const DEVICE_INFORMATION_SERVICE_UUID = '180a'

noble.on('stateChange', state => {
  console.log(`State changed: ${state}`)
  if (state === 'poweredOn') {
    noble.startScanning()
  }
})

noble.on('discover', peripheral => {
  console.log(`Found device, name: ${peripheral.advertisement.localName}, uuid: ${peripheral.uuid}`)

  if (peripheral.advertisement.localName === 'Mi Band 3') {
    noble.stopScanning()

    peripheral.on('connect', () => console.log('Device connected'))
    peripheral.on('disconnect', () => console.log('Device disconnected'))

    peripheral.connect(error => {
      peripheral.discoverServices([DEVICE_INFORMATION_SERVICE_UUID], (error, services) => {
        console.log(`Found service, name: ${services[0].name}, uuid: ${services[0].uuid}, type: ${services[0].type}`)

        const service = services[0]

        service.discoverCharacteristics(null, (error, characteristics) => {
          characteristics.forEach(characteristic => {
            console.log(`Found characteristic, name: ${characteristic.name}, uuid: ${characteristic.uuid}, type: ${characteristic.type}, properties: ${characteristic.properties.join(',')}`)
          })

          characteristics.forEach(characteristic => {
            if (characteristic.name === 'System ID' || characteristic.name === 'PnP ID') {
              characteristic.read((error, data) => console.log(`${characteristic.name}: 0x${arrayBufferToHex(data)}`))
            } else {
              characteristic.read((error, data) => console.log(`${characteristic.name}: ${data.toString('ascii')}`))
            }
          })
        })
      })
    })
  }
})

Answer 3

You can use "node-bluetooth" to send and receive data from and to a device respectively. This is a sample code:-

const bluetooth = require('node-bluetooth');

// create bluetooth device instance

const device = new bluetooth.DeviceINQ();

device
    .on('finished', console.log.bind(console, 'finished'))
    .on('found', function found(address, name) {
        console.log('Found: ' + address + ' with name ' + name);

        device.findSerialPortChannel(address, function(channel) {
            console.log('Found RFCOMM channel for serial port on %s: ', name, channel);

            // make bluetooth connect to remote device
            bluetooth.connect(address, channel, function(err, connection) {
                if (err) return console.error(err);
                connection.write(new Buffer('Hello!', 'utf-8'));
            });

        });

        // make bluetooth connect to remote device
        bluetooth.connect(address, channel, function(err, connection) {
            if (err) return console.error(err);

            connection.on('data', (buffer) => {
                console.log('received message:', buffer.toString());
            });

            connection.write(new Buffer('Hello!', 'utf-8'));
        });
    }).inquire();

It scans for the device name given in "device" variable.