Accessing movement information via node.js noble

webnicola · July 20, 2017, 10:44am

Hello!
I’m playing with stickers.
I’m using the “noble” library and the example found here:

Estimote/estimote-specs/blob/master/estimote-nearable.js

// Estimote Nearable packet is broadcast as Manufacturer Specific Data,
// with Estimote's Company Identifier, i.e., 0x015d.
// https://www.bluetooth.com/specifications/assigned-numbers/company-identifiers

// Once you obtain the Manufacturer Specific Data, here's how to parse them into
// an Estimote Nearable packet.
function parseEstimoteNearablePacket(data) { // data is a 0-indexed byte array/buffer

  // note that depending on the BLE-scanning library you use, the Company ID
  // might or might not be part of the Manufacturer Specific Data, and might
  // instead be a separate property
  //
  // most of the time, it's simply the first two bytes of the data, and that's
  // what we're assuming here
  var companyId = data.readUInt16LE(0);
  // Company ID must be Estimote's
  if (companyId != 0x015d) { return; }

  // byte 2 is "which exactly Estimote packet this is"
  // for a Nearable packet version 1 (currently the only one), the value is 0x01

This file has been truncated. show original

The only problem I find is that I can not read whether the sticker is moving or not.

I found this variable:

var isMoving = (data.readUInt8 (15) & 0b01000000) == 1;

But I always return false.

What’s the problem?

I put the stickers on a table and would like to know if it is picked up or not.

webnicola · July 24, 2017, 9:55am

Ok, i fixed.
I changed variable ‘isMoving’ in
var isMoving = (data.readUInt8(15) & 0x40) !== 0;
So, the variable is working!.

heypiotr · July 26, 2017, 10:36am

Ah, of course! A silly bug.

When the 7th bit is set to 1, the value of the entire expression is 64, not 1, so == 1 doesn’t work, but != 0 works perfectly fine.

Great catch, thanks! I updated the example.

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Accessing movement information via node.js noble

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