For fun I built an Arduino based altimeter.
Its fairly easy if you can manage a soldering iron and have a friend with a 3D printer
The code is also very basic and I´m sure someone could make a nicer display but I wanted:
Altitude sea level
Altitude relative to start of flight (starts at zero)
Altitude up or down
I used a nice small display and it all runs off a 9V rechargeable battery.
The case needs work but function I´m happy with.
Its about 60 x 70 x 25 so quite small with a 1.7" display.
Arduino mini pro (3 GBP Amazon)
Adafruit DPS310 6.6 GBP
Adafruit 1.69 Screen 15.5 GBP (probably you could go cheaper here but its a nice display)
9V rechargeable battery
Few wires and a 3D printed case.
Files are here:
So far I've uploaded my igc files to different xc portals. I used my old Garmin 76csx and gpsdump aplication. Now I have Garmin Fenix 6 and Stufly and I can't get a file with valid G-record. Will it be possible one day?