Cadence Speed Sensor

app.js

const noble = require('noble');

noble.on('stateChange', state => {
  if (state === 'poweredOn') {
    noble.startScanning(['1816']);
  } else {
    noble.stopScanning();
  }
});

noble.on('discover', peripheral => {
  console.log("discovered :" + peripheral.advertisement.localName);

  noble.stopScanning();

  explore(peripheral);

});

function explore(peripheral) {
    console.log('services and characteristics:');

    peripheral.on('disconnect', () => {
        console.log("Disconnected");
        process.exit(0);
    });

    peripheral.connect(error => {
        if (error) {
            console.log("there was an error " + error);
            return
        }

        // uuid = 1816 speed and cadence
        // uuid = 2a5b CSC Measurement
        // https://github.com/sputnikdev/bluetooth-gatt-parser/blob/master/src/main/resources/gatt/characteristic/org.bluetooth.characteristic.csc_measurement.xml
        peripheral.discoverSomeServicesAndCharacteristics(["1816"], ["2a5b"], (error, services, characteristics) => {
            if (error) {
                console.log("there was an error " + error);
                return
            }

            characteristics[0].subscribe(error => {
                if (error) {
                    console.log("there was an error " + error);
                    return
                }

                characteristics[0].on('data', (data) => {
                    // 0 is data present if 3 all are available if 2 only wheel data and only 1 cadence only
                    // 1 - 4 ints = wheel revolutions
                    // 5 - 6 ints = last wheel event time.
                    // 7 - 8 ints = crank revolutions
                    // 9 - 10 ints = last crank time

                    const first = data[4] << 24;
                    const second = data[3] << 16;
                    const third = data[2] << 8;
                    const forth = data[1];

                    console.log("first: " + first);
                    console.log("second: " + second);
                    console.log("third: " + third);
                    console.log("forth: " + forth);
                    console.log("total: " + (first + second + third + forth));

                    const event1 = data[5];
                    const event2 = data[6] << 8;

                    console.log("event1: " + event1);
                    console.log("event2: " + event2);
                    console.log("total: " + (event1 + event2));
                });
            });
        });
    });
}