Preventing GPS Tracker from sending position data prior to GPS fix

End Devices (Nodes) LMIC
1

I’m using the Lilygo T-Beam GPS-Tracker (T-Beam Meshtastic – LILYGO®).
For the software I make use of the MCCI LoRaWAN LMIC library (V4.1.1).
My software is based on the ttn-otaa example provided with the library.

Basically everything works:

  • I get position data
  • the board is connected to TTN
  • the board transmits position data via LoRaWAN

Now I would achieve the following and didn’t find a solution up to now:
I want the board to join TTN, but then send no position data before a gps fix is made and correct position data is available.

If I don’t call the do_send() function (that contains a call to the LMIC_setTxData2() function) no uplink message with position data is sent, but the board does also not join the network.
If I call the do_send() function at least one (wrong) position message is sent after joining prior to the gps fix. I can suppress subsequent uplink message but I can’t get rid of this one 1st message.

Does someone know a way to join but send uplink message only after gps fix (or more general: controlled by the application software)?

2

This will require some modifications to the internals of LMIC or for you to pick through the various function calls.

Alternatively you could just not join until you get a valid fix.

3

OK, at least good to know, that there is no easy solution that I have overlooked.
I think it depends on the application, but I also thought about joying only when GPS is ready. In my experience it takes only a few seconds to join.
And since the application for me is currently nothing more than to feed TTN Mapper that should be completely fine.
Thank you very much!

4

This topic was automatically closed 24 hours after the last reply. New replies are no longer allowed.