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Advanced Settings

These settings are for fine-tuning. The defaults work well for most installations.

AHRS Algorithm

OnSpeed supports two attitude estimation algorithms:

Algorithm Setting Characteristics
EKFQ 1 (default) 11-state quaternion Extended Kalman Filter. Estimates attitude, gyro biases, vertical velocity and altitude, vertical-accel bias, and sideslip. Optuna-tuned against a VectorNav VN-300 reference. No magnetometer, no GPS.
Madgwick 0 Complementary filter, quaternion-based. Low CPU cost.

A fresh install boots into EKFQ. Either algorithm is selectable from the web interface; the choice is saved to the configuration as AHRS_ALGORITHM.

Recalibrate if you switch algorithms

EKFQ derives AOA from a kinematic formula rather than tracking it as a filter state, so per-flap AOA curves fit under one algorithm can read slightly differently under the other. Run the calibration wizard after changing AHRS_ALGORITHM if the tones shift relative to your reference.

AOA Smoothing

Controls the Exponential Moving Average (EMA) filter applied to the AOA signal.

  • Default: 10 (samples)
  • Lower values: More responsive but noisier — the tone will fluctuate more in turbulence
  • Higher values: Smoother but slower response — the tone may lag behind rapid AOA changes

For most aircraft, the default of 10 provides a good balance of responsiveness against the audio path's natural smoothing through the DAC.

Pressure Smoothing

Controls EMA filtering on the pitot, AOA, and static pressure readings.

  • Default: 15 (samples)
  • Lower values: Faster response, more noise
  • Higher values: Smoother, more lag

CAS Curve (Calibrated Airspeed)

If your aircraft has a known airspeed calibration curve (correcting IAS to CAS), you can enter polynomial coefficients here:

  • Type: 1 (polynomial)
  • Coefficients: X3, X2, X1, X0 (cubic polynomial)
  • Enabled: false by default

Most aircraft don't need this — the default is a pass-through (X1=1.0, all others=0.0).

Only enable this if you have a measured position error correction curve for your pitot/static system. An incorrect CAS curve is worse than no curve at all.

Serial Output Format

Controls the format of data sent on the display serial output (GPIO 10):

  • ONSPEED — OnSpeed native format
  • G3X — Garmin G3X-compatible format

Use G3X if you're feeding data to a Garmin display. Otherwise, leave as ONSPEED.

Data Source

Controls where the AOA data comes from:

Source Use
SENSORS Normal operation — live sensor data
TESTPOT Test mode — AOA from a test potentiometer
RANGESWEEP Test mode — automatic AOA sweep 0–20°
REPLAYLOGFILE Replay a recorded log file through the system

For normal flight operations, this should always be set to SENSORS.

Calibration Source

Controls which IAS source the calibration wizard uses:

  • ONSPEED — use OnSpeed's own pitot/IAS
  • EFIS — use the EFIS-provided IAS

If you have an EFIS connected with accurate IAS, using EFIS may give better calibration results.