This project is a beacon for drones in France. The French government mandates that each drone broadcasts its position and home position via an 802.11 beacon frame using a custom extension. This clearly makes most existing drones illegal.
There are several beacons for sale that broadcast the required information. However, I discovered an open source project that used a Liligo TTGO T-Beam board that contains an ESP32 with Wifi and a GPS chip.(it also contains a LORA chip.) This project was written by Pierre Kancir.
The code was, however, not structured in the way I like it and it was not easy to see what was going on. It also took some time to get started because it used platform.io and Arduino. I threfore rewrote the project and threw away a lot of unnecesary code. It now also only uses Arduino, there are no other dependencies.
You should place the drone-ttgo folder in your Arduino folder. On the mac this is ~/Documents/Arduino. Then clock on the drone-ttgo.ino file. This should open your Arduino IDE. You can import the library folders via the IDE (Sketch/Include Library, although it says ZIP, you can also choose folders.) Do this for all folders in the libraries folder. A shortcut is to copy these folders directly to ~/Arduino/libraries.
To install the Liligo T-Beam board in Arduino see here
All the code is now in a single file. Since this is legal stuff, I've translated the law and put the articles next to the code implementing it.
One of the problems was the lack of information about the 802.11 standard since it is very expensive. I've tried to document my finding as good as possiible.
My primary testing took place with the MacOS sniffer. If you click on the Wifi icon in the top bar
while pressing the option key you get an extra large menu with lots of wifi info. You can then
Open Wireless Diagnostics. In the top menu, you can then open 'Sniffer'. This tool
can be used to sniff channel 6. The output is stored in /var/tmp after you stopped. These
files can be viewed in Wireshark. Theoretically it should be possible
to directly sniff in Wireshark but I've not been able to get there.
Since listening is not trivial due to security problems on MacOS, the code also broadcasts a copy of the payload over UDP to port 2000. This might disappear at one point.
The code is licensed GPL. Whatever.
If you want to contribute ... send a PR.