As I love paragliding, I decided to build my own variometer, as most of them are very expensive. I needed something easy to interface, and I found a simple way to interface with kobo, and smartphones. You can connect it via bluetooth or wired, sending the informations to a serial port. it has it’s own buzzer, so it can work as standalone also. The project is not so difficult but I needed a bit of time to find the right arm board.


If any pilot wants to build his own vario, just keep in mind that all the plans are given as they are, and there could be some error in the code. I won’t be responsible for any damage or mistake caused from a malfunction about the vario.


  • It has a very high resolution, about 10 cm.
  • GPS stream
  • you can choose between raw readed pressure and filtered pressure (with Kalman algorithm)
  • Parameters adjustable when you select filtered pressure.
  • Long lasting battery (up to 10h and more)
  • Bluetooth
  • If you don’t need bluetooth you can reada data from hardware serial.
  • You can deactivate the beep, in case you use the smartphone audio.
  • xctrack full compatible.
  • xcsoar full compatible.
  • lk8000 full compatible.
  • Compact box (approx 6x4x2cm)


Components, connections and code

  • Teensy LC
  • ms5611 barometer
  • buzzer
  • hc-05 bluetooth module
  • 3v battery
  • PA6H GPS module
  • TP4056 bettery charger module


If you have some skills about soldering you can build it very easy, just follow the connection scheme in the picture. You just have to trick a bit to squeeze all the components inside the box, but as you can see it’s possible.

Module hc-05 is perfect for this application, but just check that it is setted at 9600bps. You can use uart1.ino to play with it and set it up. I attached also the hc05 datasheet and manual, in case you need to change some parameters.

Mediatek PA6H GPS module is very good module. It fix a cold signal within 45 sec or less. It is already setted at 9600bps, and sends the position one time per second which is good enough for this application.

Teensy is compatible with arduino IDE, so just compile the code, and try it.

HC-05 AT Command Ref
PA6H commands


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