Combining burst fragments into complete bursts

Dec 1, 2022 · 2 minutes to read

This article describes how to merge burst fragments into complete bursts.

Introduction

Each burst will have unique¹ measurement id e.g: "MeasurementId":225 and burst id e.g: "BurstId":133. You should identify your burst with this information along with SensorNodeId.

After you have your burst fragments you can start combining them into complete bursts with their "Values", "Valuemapping", "BurstDataOffset" and "DataSize"-fields where:

How bursts are split into fragments

Bursts are split into smaller fragments and sent via wirepas to gateway which sends them to cloud. Each fragment contains partial array of the data-bytes from the complete burst. Because these fragments cannot be guaranteed to come in correct order and some might be missing they have field "BurstDataOffset" which tells to whoever processes nodes messages that this bursts fragment starts at at this byte-offset.

Below figure should illustrate how burst offset works:

In addition to all of this data sent there is also field "FragCount" which should never be used when reconstructing the complete burst. Field "FragCount" is added by the gateway and is just incrementing counter of how many fragments have arrived to the gateway. This means that if a fragment with "BurstDataOffset" of 96 would come before fragment with "BurstDataOffset" of 0 it would get smaller "FragCount" than the fragment with offset of 0.