WIP - Puck.js reading CSC (cycling speed cadence) BLE sensor to replace bike computer head unit with Puck.js or (later) Pixl.js

Hi everybody and esp. Gordon (thanks for Espruino!!),

I'm looking into receiving sensor readings from the commercially sold CSC sensor Wahoo Speed (https://www.amazon.com/Wahoo-Cycling-Spe­ed-Sensor-Bluetooth/dp/B01DIE7LUG/ref=sr­_1_3?s=sporting-goods&ie=UTF8&qid=153245­8958&sr=1-3&keywords=wahoo+speed) which came with my bike computer Wahoo ELEMNT Mini, of which I want to replace the cumbersome headunit.

The sensors sends data via BLE with the CSC service:

https://blog.bluetooth.com/part-2-the-wh­eels-on-the-bike-are-bluetooth-smart-blu­etooth-smart-bluetooth-smart

https://www.bluetooth.com/specifications­/gatt/viewer?attributeXmlFile=org.blueto­oth.characteristic.csc_measurement.xml

Using NRF connect on Android, the sensor readings are shown easily after enabling the notification.

Now to the crucial part (for me):
This code:

var gatt;
NRF.requestDevice({ filters: [{ namePrefix: 'Wahoo' }] }).then(function(device) {
  console.log(device);
  return device.gatt.connect();
}).then(function(g) {
  gatt = g;
  return gatt.getPrimaryService("1816");
}).then(function(service) {
  console.log("Service:" + service);
  return service.getCharacteristic("0x2A5B");
}).then(function(characteristic) {
  return console.log(characteristic);
}).then(function() {
  gatt.disconnect();
  console.log("Done!");
});

gives me this output:

 ____                 _
|  __|___ ___ ___ _ _|_|___ ___
|  __|_ -| . |  _| | | |   | . |
|____|___|  _|_| |___|_|_|_|___|
         |_| espruino.com
 1v99 (c) 2018 G.Williams
>
=undefined
BluetoothDevice: {
  "id": "df:b3:22:19:bd:8e random",
  "rssi": -60,
  "data": new Uint8Array([2, 1, 6, 3, 3, 22, 24, 17, 9, 87, 97, 104, 111, 111, 32, 83, 80, 69, 69, 68, 32, 54, 51, 70, 49]).buffer,
  "name": "Wahoo SPEED 63F1",
  "services": [
    "1816"
   ]
 }
Service:[object Object]
BluetoothRemoteGATTCharacteristic: {
  "uuid": "0x2a5b",
  "handle_value": 36, "handle_decl": 35,
  "properties": { "broadcast": false, "read": false, "writeWithoutResponse": false, "write": false,
    "notify": true, "indicate": false, "authenticatedSignedWrites": false }
 }
Done!

Can anyone point me in the right direction how I can enable and receive the CSC measurement? Sorry I'm a dummy with programming/JavaScript...
The path to go I imagine would probably consist of writing to 0x2902 characteristic to enable notifications and have some kind of callback receive and interpret the data.

Later on I plan on using the new MDBT42Q Breakout, connecting a Waveshare epaper display and 3d print a small case and have it running on a 18650 battery. Another option would be to use Pixl.js with a custom case and some kind of battery managment.

Thanks for any help!!
Best regards,

Joost