AltiVario

Open-source variometer for paragliding and hang gliding. Two hardware variants sharing common libraries.

Versions

AltiVario Legacy (ATmega328P + BMP085)

Refactored version of the original vario.ino with bug fixes:

• Ring buffer averaging (fixes out-of-bounds array access)
• unsigned long timestamps (fixes float precision loss at ~4.6 hours)
• Division-by-zero guard in linear regression
• Missing break statements in switch/case (audio)
• Zero-heap NMEA formatting via snprintf() (eliminates String class fragmentation)
• Watchdog timer and I2C bus recovery

AltiVario ESP32 (ESP32-S3 + MS5611)

Full-featured variometer with FreeRTOS multi-task architecture:

• MS5611 barometric sensor at 50Hz with CRC4 validation
• BLE telemetry (NimBLE UART service) — compatible with XCTrack/XCSoar
• OLED display (SSD1306 128x64) — 3 pages: Flight, Stats, Settings
• GPS (u-blox NEO-6M) with airborne mode, glide ratio computation
• IGC flight logging to MicroSD card with 512-byte write buffer
• WiFi configuration portal — captive portal for settings and log download
• Dual audio — piezo (LEDC PWM) and DAC speaker (MAX98357A via I2S)
• Auto flight detection — launch/landing state machine
• NVS-backed configuration — persists across reboots

Repository Structure

AltiVario/
├── libraries/                    # Shared Arduino libraries
│   ├── AltiVario_Vario/          # VarioComputer, AveragingFilter, pressureToAltitude()
│   ├── AltiVario_NMEA/           # LK8EX1 + Flymaster F1 formatting (zero-heap)
│   └── AltiVario_Audio/          # AudioPatternEngine (tone params from vario rate)
├── AltiVario_Legacy/             # ATmega328P sketch
└── AltiVario_ESP32/              # ESP32-S3 sketch with FreeRTOS tasks
    └── data/                     # WiFi portal web assets

ESP32-S3 Pin Assignments

Function	Pin	Notes
I2C SDA	GPIO 8	MS5611 + SSD1306
I2C SCL	GPIO 9
GPS RX	GPIO 17	NEO-6M TX
GPS TX	GPIO 18	NEO-6M RX
SD CS/MOSI/SCK/MISO	GPIO 10/11/12/13	SPI
Piezo	GPIO 38	LEDC PWM
I2S DAC	GPIO 4/5/6	BCLK/LRCLK/DOUT
Button	GPIO 0	Boot button
Battery ADC	GPIO 1	Voltage divider

Dependencies

Legacy: Wire, BMP085, Tone, AltiVario_* shared libs

ESP32-S3: Wire, MS5611, NimBLE-Arduino, U8g2, TinyGPS++, SD, ESPAsyncWebServer, AsyncTCP, Preferences, AltiVario_* shared libs

Setup

1. Symlink shared libraries to your Arduino libraries folder:

   ln -s $(pwd)/libraries/AltiVario_Vario ~/Arduino/libraries/
   ln -s $(pwd)/libraries/AltiVario_NMEA ~/Arduino/libraries/
   ln -s $(pwd)/libraries/AltiVario_Audio ~/Arduino/libraries/

2. Install board support:

   • Legacy: Arduino AVR Boards
   • ESP32: ESP32 Arduino Core (Espressif)

3. Install library dependencies via Arduino Library Manager.

4. Open the appropriate .ino sketch and upload.

Power Budget (ESP32-S3 flight mode)

~200-250 mA total. 2000 mAh LiPo = ~8-10 hours, 3000 mAh = ~12-15 hours.