Proximity beacons parsing - subframe always the same?

zualexander · January 22, 2019, 3:35pm

Hello,

we are trying to get the acceleration data from the ltest proximity beacons via parsing it, describing in your github-spec repository:

github.com

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

// Packest from the Estimote family (Telemetry, Connectivity, etc.) are
// broadcast as Service Data (per "§ 1.11. The Service Data - 16 bit UUID" from
// the BLE spec), with the Service UUID 'fe9a'.
var ESTIMOTE_SERVICE_UUID = 'fe9a';

// Once you obtain the "Estimote" Service Data, here's how to check if it's
// a Telemetry packet, and if so, how to parse it.
function parseEstimoteTelemetryPacket(data) { // data is a 0-indexed byte array/buffer

  // byte 0, lower 4 bits => frame type, for Telemetry it's always 2 (i.e., 0b0010)
  var frameType = data.readUInt8(0) & 0b00001111;
  var ESTIMOTE_FRAME_TYPE_TELEMETRY = 2;
  if (frameType != ESTIMOTE_FRAME_TYPE_TELEMETRY) { return; }

  // byte 0, upper 4 bits => Telemetry protocol version ("0", "1", "2", etc.)
  var protocolVersion = (data.readUInt8(0) & 0b11110000) >> 4;
  // this parser only understands version up to 2
  // (but at the time of this commit, there's no 3 or higher anyway :wink:)
  if (protocolVersion > 2) { return; }

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thanks for providing a very good code example!

Our problem is, that (according to the estimote-telemetry.js ), the beacon always sends subframe B, and in subframe-b, the acceleration-data is missing.

Do we have to change the configuration of the beacons to send this data, or may there be a problem on our side with the parsing?

how should it work in general? one time the A-Frame is send, one time the B-Frame?
thanks in advance!

BR Alex

heypiotr · January 22, 2019, 4:10pm

The beacon will take turns transmitting Telemetry A and Telemetry B. For example, if you have Telemetry advertising interval set to 2570 ms, then beacon will broadcast Telemetry A, then wait 2570 ms, then broadcast Telemetry B, then wait 2570 ms, then back to A, etc.

zualexander · January 23, 2019, 9:21am

hi, thanks for your fast reply!

the strange thing is, that 2 consecutive packages have completely the same data in the array buffer. could it be, that there is a different macaddress used for telemetry A and telemetry B packages?

thanks

heypiotr · January 23, 2019, 12:03pm

Both should have the same physical address. Maybe your receiver/receiving software skips some packets? If you let it run long enough, do you observe both kinds of sub-frames?

zualexander · January 29, 2019, 1:27pm

Hi,

I’m not sure if the receiver-software is the problem. We are trying to create an ionic-app, and use the ‘@ionic-native/ble’; plugin to scan for bluetooth devices. Are you familiar with this plugin or have you already used it to read the telemetry data?

BR Alex

heypiotr · January 31, 2019, 8:19am

What do you run this on, iOS/Android? Bluetooth in iOS/Android is a shared resource, used by many apps & system services, which means their Bluetooth stacks generally do some flow control, which in turn means you don’t always get all the packets your app wants.

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Proximity beacons parsing - subframe always the same?

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