EFU Documentation

Complete user guide and technical information

Version 1.7

IMPORTANT: EFU is for situational awareness only. Do not use as a primary certified instrument. User assumes responsibility.

1. System overview

EFU is a compact EFIS for GA, combining variometer, altimeter (QNH/QFE), attitude (AHRS), GPS and auxiliary functions.

Designed for panel mount with a clear UI and basic sensor calibration for real flight conditions.

2. Installation and power

Power: 5–35 V DC (wide input). Reverse polarity protected.
Ground: solid common ground required for EMI immunity.
AHRS (UART2): connect the AHRS module to the designated port.
GPS (UART3): connect GPS receiver. Ensure sky visibility.
Pressure sensors (I2C): static @0x77, pitot @0x76.
Mounting: stress-free panel mount, within aviation vibration limits.

3. Controls and UI

Encoder: rotate to navigate/change values; press to select/confirm.
Main screen: attitude, speed, altitude, variometer, GPS fields (GS/COG/ALT).
Status indicators: Snsr Err (sensors), speed warnings, GPS/AHRS loss.

4. Technical specifications (brief)

Hardware

MCU: 32‑bit
Interfaces: UART, I2C, USB
Memory: Flash/EEPROM per model

Display

Type: 4.3" TFT
Resolution: 480×272
Touch: resistive/capacitive

Environment

Temp: −20…+60 °C
Vibration: aviation level
Power: 5–35 V DC

5. Flight instruments

Artificial horizon (AHRS)

Roll/pitch with marks
Dynamic sky/ground palette
Magnetometer-based heading with auto-calibration
Requires calibration for accuracy

Altimeter (QNH/QFE)

QNH sea level
QFE field elevation (zero on ground)
Manual pressure correction

Variometer (VSI)

Adjustable range and sensitivity
Adaptive smoothing
Units: m/s or ft/s

Airspeed (IAS) and arcs

White: flaps range
Green: normal
Yellow: caution; Red: VNE
Blue: best glide

GPS fields

GS — ground speed
COG — course over ground
ALT — GPS altitude (aux)

6. Menus and settings

Below are key configuration items and their purpose. Adjust on ground and note original values.

Parameter	Purpose	Range	Units
Red Line VNE	Max speed (never exceed)	60–400	km/h/kt/MPH
Green Arc Start	Start of normal flight arc	30–250	km/h/kt/MPH
Green Arc End	End of normal flight arc	30–250	km/h/kt/MPH
White Arc Start	Start of flaps arc	30–250	km/h/kt/MPH
White Arc End	End of flaps arc	30–250	km/h/kt/MPH
Blue Line	Best glide speed	30–250	km/h/kt/MPH
QNH/QFE	Barometric mode	QNH/QFE	hPa/inHg/mmHg
Static Calib.	Static sensor calibration	-10…+10	units
Pitot Calib.	Airspeed sensor calibration	-70…+70	units
Vario Sens.	Variometer sensitivity	-5.5…+5.5	coef
Vertical Speed	VSI scale range	5–50	m/s or ft/s
Speed Unit	Speed units	Knots/MPH/km/h	—
Altitude Unit	Altitude units	Feet/Meters	—

7. Calibration

AHRS calibration (precise)

Level surface, nose to magnetic north
Menu: CALIB → RESET AHRS → Zero & Save
Do not move 30–60 s
Finish and restart/return

Pressure sensors calibration

Static: set by field elevation (≈ 8 m/step)
Pitot: set by IAS vs GPS/reference (≈ 1 MPH/step)

8. Troubleshooting

Red X — AHRS lost: check UART2, power, recalibrate
Snsr Err red: check I2C (0x77/0x76), power, wiring
No GPS: antenna and sky view; wait for fix
Wrong altitude: verify QNH/QFE and Static Calib.

9. Disclaimer

Use EFU at your own risk. For critical decisions, rely on certified avionics only.

10. Support & resources

Website: eFlyUnit.com. Contact via official website.