TTNHABBridge

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Project TTNHABBridge
350px
A software bridge between TTN and the HAB network
Status In progress
Contact bertrik
Last Update 2017-08-01

This idea is about using the-things-network as a receiver for amateur balloon telemetry.

Receiving telemetry from amateur balloons is currently typically done on the 434 MHz band using RTTY modulation, sending ASCII strings to dedicated receivers. The operator of each receiver has to be prepared for receiving the telemetry, by tuning to the correct frequency at the correct time, setting up a dedicated software client that decodes the RTTY modulation and forwards the data to a central system over the internet. The central system accepts data from many such receivers, performs deduplication, keeps track of who received what and updates a nice graphical map of where each balloon is and where the receivers are.

A network like the-things-network can help a lot, it has a lot of gateways already (in the netherlands at least..), already performs deduplication. Also LoRa as a modulation scheme is much more sensitive than RTTY.

In short, the idea is:

  • you attach a LoRaWAN transmitter to the balloon
  • the LoRaWAN transmitter is pre-configured with a set of keys generated by the TTN
  • the bridge software listens for packets received by the TTN and decodes the payload data into an id, latitude, longitude, altitude of the balloon
  • for each packet, we know which gateways received it and where they are. So we can "fake" a client for each gateway and construct an ASCII sentence according to the HAB server conventions
  • the HAB server still sees the same messages like it would if there many traditional receivers, so doesn't need any modification.

This way, the entire things network can be used to receive balloon telemetry! There is no longer a need for operators to be present at their receiver at the exact time the balloon is launched, making manual adjustments, etc. The Netherlands is already covered by many TTN gateways, greatly increasing the chance the balloon telemetry will be picked up.

Stuff to do:

  • come up with a simple but flexible way to encode telemetry in a binary packet, to be transmitted over TTN.
  • figure out how to receive data from TTN, I think this is an MQTT stream
  • figure out how to find the coordinates of each TTN gateway
  • figure out the protocol between dl-fldigi and the HAB server
  • implement this (in Java for example)!