KiwiH743-Wing Flight Controller

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Overview

The KiwiH743-Wing is a Pixhawk-format flight controller system consisting of two boards: a Flight Controller and a Power Distribution Board (PDB). Designed for expendable quadcopters and long-range fixed-wing drones. Ready to use with Rover, Wing, Quadcopter, and Hexacopter configurations.

Premium features: GPS-less takeoff, IRC Tramp VTX control, VRX integration (TBS Fusion, Skyzone Steadyview), wind override from GCS.

Firmware

Three ArduPilot branches are maintained in parallel: 4.5 (Plane-4.5.7 LTS), 4.6 (current), and 4.7. Pick the one that matches your fleet.

The no IMU CLKIN builds are an A/B test control with the external 32.768 kHz IMU clock disabled — IMUs run on their internal oscillators. Same APJ_BOARD_ID, loads with the same bootloader.

The INAV zip contains the .hex (target KIWIH743WING) plus the target sources and a README — flash the hex via the INAV Configurator “Load Firmware [Local]” button.

Previous versions

Features

• STM32H743 MCU (480 MHz, 2 MB flash)
• 12S power supply
• 5V, 6/7V, 9/12V 5A BECs
• ICM-42688P and ICM-45686 with power and hardware signal filtering
• BMP388 barometer
• Dual camera input, switchable
• 12 PWM outputs + 3 GPIO/PINIO outputs (servo 13-15)
• 5 UARTs, UART7 with flow control
• 1 SPI, 1 I2C, FDCAN
• 5 GPIOs, 2 relay outputs, 9/12V switch
• Analog + digital VTX output
• STM32G4 OSD
• SD card via SDMMC
• 40 x 42 mm board, 36 x 39 mm mounting holes

Technical Specifications

Processor

Sensors

Power

Mechanical

Serial Ports

Ports without DMA fall back to interrupt + FIFO and are not deterministic at high baud.

High-baud MAVLink ports

For peripherals that need >115 k baud (e.g. ELRS+MAVLink, RTK GPS+MAVLink), use the DMA-backed UARTs:

Default firmware already sets SERIAL7_PROTOCOL = MAVLink2 on the Wing, so for a second high-baud link just set SERIAL7_BAUD = 460.

Connectors and Wire Colors

Port connection diagram for cable assembly. Pin order in each connector matches the silkscreen labels on the board, read left to right.

Wire Color Legend

Note: Wire colors are intended to simplify cable assembly and connector identification. Signal names printed on the PCB always take precedence over wire color. On the VTX cable, 5V is the video 5V rail (blue) — distinct from 12V (red).

AUX, RELAY and ADC Connectors (bottom side)

Three JST-SH 1 mm connectors on the bottom of the FC board. Pin order follows the silkscreen next to each connector.

AUX (8-pin). 3.3 V logic straight from the MCU, no driver, no series resistor. 5V is a supply output.

U1-U4 are outputs, low at boot. Use them with RELAYn_PIN=105/106/107/108 and RELAYn_FUNCTION=1. From Lua, use gpio:write(105, 1). All six ArduPilot relays have a default pin, so free one first. Example: RELAY6_PIN=105 if servo 15 is not needed as GPIO.

RELAY (4-pin). Two high-side switched power outputs from the board’s 12 V rail (9 V when the rail is set to 9 V). Each output is a P-channel MOSFET (IRLML5203) driven through a level shifter with a 10 k gate pulldown. The output is off while the MCU is in reset or unprogrammed. Off = open circuit, not 0 V. Rate each output at 2 A continuous.

The X1/X2 connector pins are the same outputs as the RELAY 1 / RELAY 2 pads listed under GPIOs, Relays, and AUX.

ADC (6-pin). Analog inputs, each with an ESD diode and 100 nF to ground. A1-A3 are 0 to 3.3 V direct. B2 is a battery voltage input with a 100 k / 5.1 k divider, ratio 20.6. Full scale 3.3 V is about 68 V at the pin. 5V is a supply output.

Second battery monitor on B2: set BATT2_MONITOR=3, the firmware defaults BATT2_VOLT_PIN=13 and BATT2_VOLT_MULT=20.6 (firmware after 2026-10-14). A1/A2/A3 suit an analog airspeed sensor (ARSPD_PIN=11) or RSSI (RSSI_TYPE=1, RSSI_ANA_PIN=10).

GPIOs, Relays, and AUX

Dedicated GPIO Pads

Note: pad silkscreen numbers and ArduPilot relay numbers are off by one. ArduPilot RELAY1 is the camera switch (RELAY1_PIN=100, PE2, hwdef default). Pad RELAY 1 (PD3) is ArduPilot RELAY2, pad RELAY 2 (PD4) is ArduPilot RELAY3. Both are enabled by default, off at boot. RELAY4-6 default to servo outputs 13-15, see below. RELAY 1/2 pads are 9/12V switched outputs.

PWM Outputs

Any PWM pin can be turned into a GPIO with SERVOn_FUNCTION=-1 + RELAYn_PIN=<gpio>. Reboot after changing the function.

Bidirectional DShot (ESC RPM telemetry) is available on outputs 1–3 (TIM1). Enable with SERVO_BLH_BDMASK=7 and use DShot300/600 on those outputs.

Servo 13-15 as GPIO (PINIO)

Servo outputs 13, 14 and 15 ship as GPIO outputs, not PWM. The firmware defaults set SERVO13-15_FUNCTION = -1 and map the pins to RELAY4-6, off at boot.

Signal level is 3.3 V through a 220 R series resistor, active high. The pin drives up to 15 mA, enough for a logic input or an opto, not for a coil.

To drive one from a transmitter switch, put the option value on an RC channel, for example RC9_OPTION = 36 for RELAY4 on servo 13. Switch low (< 1200 us) = off, high (> 1800 us) = on.

param set RC9_OPTION 36     # RC9 switches RELAY4 (servo 13)
relay set 3 1               # RELAY4 ON from MAVProxy
relay set 3 0               # RELAY4 OFF

To get a PWM output back, set SERVOn_FUNCTION to the wanted function and RELAYn_FUNCTION = 0. No firmware rebuild is needed.

Pyrotechnic and one-shot loads

These three outputs are the ones to use for a parachute, cutter or other load that must never see a stray pulse:

• The bootloader drives them low from the first milliseconds. The firmware presets the output latch low. There is no pulse during startup or relay init.
• The pins are high impedance only while the MCU is held in reset or in DFU mode. If the load input is a bare MOSFET gate with no pulldown, fit a pulldown at the load. Use 4.7 k to 100 k from signal to GND. A module with an opto input, a base resistor or its own pulldown does not need it. Check with a meter: resistance from the module input to GND below 1 M means a pulldown is there.
• Keep RELAYn_DEFAULT = 0. Value 2 restores the last state after a reboot and can re-fire the load.
• Do not change SERVO13-15_FUNCTION on a channel wired to a pyro load. A servo function puts 50 Hz pulses on the pin.

For a parachute, prefer the built-in parachute function over a raw relay switch. It adds the disarmed lockout, CHUTE_ALT_MIN and a timed pulse instead of a held level:

param set RELAY4_FUNCTION 3   # Parachute on servo 13
param set CHUTE_ENABLED 1
param set CHUTE_TYPE 10        # relay
param set RC9_OPTION 22        # parachute release switch

Relay Usage

MAVProxy:

relay set 0 1    # RELAY1 ON (CAM SW HIGH)
relay set 0 0    # RELAY1 OFF
relay set 1 1    # RELAY2 ON (RELAY1 pad HIGH)

Mission waypoint: DO_SET_RELAY — relay number 0-based (0=RELAY1), setting 1=ON / 0=OFF.

Lua:

relay:toggle(0)  -- toggle RELAY1 (CAM SW)
relay:on(1)      -- RELAY2 ON (RELAY1 pad)
relay:off(1)     -- RELAY2 OFF

All GPIO pads default LOW on boot. Use RELAY_DEFAULT params to set initial state.

OSD Reset (RELAY6):

RELAY6 defaults to servo output 15. To use it for the STM32G4 OSD reset line (VID NRST) instead, point it at GPIO 104. Active low — set RELAY6_INVERTED=1 so that “relay on” pulls the line low (reset) and “relay off” releases it.

param set RELAY6_PIN 104
param set RELAY6_FUNCTION 1
param set RELAY6_INVERTED 1
relay set 5 1   # reset OSD
relay set 5 0   # release reset

Power Monitoring

Current

Sensor Calibration

Battery Voltage Thresholds (ArduPilot)

Buses

SPI

I2C

FDCAN

SDMMC (SD Card)

Premium Features

GPS-less Takeoff (ArduPlane)

KIWI firmware supports autonomous takeoff without a GPS fix. Useful for hand launch or catapult deployment in GPS-denied environments.

Parameters:

Procedure:

1. Power on, wait for EKF convergence
2. Set home (from GPS before loss, or manually via MAVLink)
3. Arm in FBWA mode
4. Switch to TAKEOFF mode

IRC Tramp VTX Control

Full IRC Tramp protocol support under ArduPilot. Change VTX power, band, channel, and pit mode directly from your GCS or OSD — no need for SmartAudio.

Works with TBS Unify, Rush Tank, and other Tramp-compatible VTXs.

VRX Integration (TBS Fusion / Skyzone)

Working video receiver control under ArduPilot. Supports:

• TBS Fusion — band/channel tracking via CRSF
• Skyzone Steadyview — auto channel sync

Wind Override from GCS

The GCS can set the wind that the autopilot uses for dead reckoning. This helps in GPS-denied flight, where the EKF cannot learn the wind by itself. Available in ArduPilot 4.6 firmware, all vehicles.

The GCS sends the MAVLink message WIND (#168) to the autopilot:

Behavior:

• The autopilot applies the wind to the EKF3 (all lanes) and to DCM within 1 s.
• The autopilot reports the wind that it uses in its outgoing WIND message. The GCS can compare this value with the set value.
• The EKF continues to refine the wind from airspeed or sideslip data, if available. The set value is the start point.
• The autopilot sends a status text: Wind override 270 deg 8.0 m/s (sysid/compid) or Wind override off (sysid/compid).
• If the GCS sends no WIND message, the autopilot operates as standard ArduPilot.
• The override stays active until the GCS turns it off or the EKF resets. After a reboot, the GCS must send the wind again.

Example (pymavlink):

m.mav.wind_send(270.0, 8.0, 0.0)   # wind from 270 deg at 8 m/s
m.mav.wind_send(0.0, 0.0, 0.0)     # override off

The autopilot accepts WIND from any system ID. If other autopilots share the same MAVLink network, set SYSID_ENFORCE 1 so that the autopilot accepts commands only from its GCS (SYSID_MYGCS).

Camera Gimbal Support

KiwiH743-Wing supports camera gimbals out of the box — both servo-based and MAVLink protocol gimbals (CADDX GM3 V2 and compatible).

MAVLink Gimbal

Wire gimbal UART to any free serial port (gimbal TX → FC RX, gimbal RX → FC TX, GND).

RC Control

Assign RC channels to control gimbal axes:

Example: with MNT1_RC_RATE=60, moving the RC6 stick deflects pitch at 60°/s. Set MNT1_RC_RATE=0 for direct angle control (stick position = gimbal angle).

Gimbal firmware must be V2.0 or higher.

Servo Gimbal

Connect pitch/yaw servos to any Servo PWM outputs (SERVO 9–SERVO 15).

Displayport OSD

HD OSD via MSP Displayport on SERIAL8 (OSD UART). Compatible with DJI O3, HDZero, Walksnail.

param set OSD_TYPE 5
param set OSD_UNITS 0
param set MSP_OPTIONS 4
param set MSP_OSD_NCELLS 0
param set SERIAL8_BAUD 115
param set SERIAL8_OPTIONS 0
param set SERIAL8_PROTOCOL 42

OSD under INAV

The onboard STM32G4 OSD is a character OSD driven over MSP DisplayPort on UART8, the same link ArduPilot uses. INAV draws a 30x16 character grid onto the analog video.

How it works:

1. INAV opens UART8 as an MSP DisplayPort port (function MSP DisplayPort in the Ports tab, 115200 baud).
2. osd_video_system defaults to BF43COMPAT, which matches the font built into the OSD module. INAV draws all symbols, the artificial horizon and the direction arrows with that font.
3. Font upload from the INAV Configurator is not used on this board. Keep the OSD module’s built-in font.

Factory defaults, applied on defaults or first boot:

Equivalent CLI, if the settings were changed or a config from another board was loaded:

serial 7 33554432 115200 115200 0 115200
set osd_video_system = BF43COMPAT
feature OSD
save

Options you may want to change:

Element positions are set in the Configurator OSD tab or with osd_layout. The layout below keeps every element inside columns 1 to 28 and rows 1 to 12 so nothing is lost to analog overscan. Column and row are zero based, V is visible, H is hidden:

osd_layout 0 14 2 1 V      # satellites
osd_layout 0 0 7 1 V       # RSSI
osd_layout 0 24 13 1 V     # heading
osd_layout 0 1 22 1 V      # battery voltage
osd_layout 0 15 22 3 V     # altitude
osd_layout 0 26 22 4 V     # vertical speed
osd_layout 0 13 22 5 V     # ground speed
osd_layout 0 3 8 6 V       # artificial horizon
osd_layout 0 9 2 6 V       # throttle
osd_layout 0 11 2 7 V      # current
osd_layout 0 12 2 8 V      # mAh used
osd_layout 0 10 2 9 V      # VTX channel
osd_layout 0 22 14 9 V     # home arrow
osd_layout 0 7 2 10 V      # flight mode
osd_layout 0 23 13 10 V    # home distance
osd_layout 0 28 20 11 V    # on time / fly time
osd_layout 0 30 1 12 V     # messages

Checks in the CLI:

status

The OSD: line must read MSP DisplayPort: DJI Compatability mode [30 x 16]. Any other OSD line means the port function or osd_video_system was changed.

VTX control under INAV uses IRC Tramp on UART2 (function VTX Tramp). Only the two Tramp bands that overlap the module’s factory table are reachable from INAV: INAV band A is vendor band I, INAV band E is vendor band K. Power levels are 25 mW, 2 W and 4 W.

Flight Controller

Built around the STM32H743, the flight controller provides dual IMUs with hardware signal filtering, dual switchable camera inputs, and relay-controlled power outputs.

Power Distribution Board (PDB)

Features

• 4S–12S power input
• 5V 5A output
• 5/6/7/9V 5A adjustable output
• 12V 5A output
• 3.3V 1A output
• 0.1 mOhm current sensor
• 36 x 39 mm mounting holes
• 42 x 75 mm board dimensions

Other

Full Pinout Reference

Port A (PA)

Port B (PB)

Port C (PC)

Port D (PD)

Port E (PE)