NxtPX4v2 User Manual

Product Overview

NxtPX4v2 is a compact, high-performance flight controller developed from the HKUST Aerial Robotics / Nxt hardware family. It features an STM32H743 MCU, dual BMI088 IMUs, an SPL06 barometer, and microSD storage, along with 7 UARTs, 8 PWM outputs, external I²C and SPI buses, and independent 5 V / 12 V BECs. The flight controller supports both ArduPilot and PX4 and is well suited to UAV projects that require substantial processing performance, redundant IMU sensing, and open hardware resources.

Project on GitHub

Hardware on GitHub

Key Features

Purchase

MicoAir Tech Store

Hardware Specifications

Processor and Sensors

The STM32H743VIH6 provides a 480 MHz clock speed and 2 MB of Flash. Two BMI088 IMUs provide independent inertial measurements for sensor-consistency checks and redundancy. The SPL06 provides barometric altitude measurements.

NxtPX4v2 does not include an onboard magnetometer. When heading information is required, connect a GPS module with an integrated magnetometer or a standalone magnetometer through the external I²C bus.

Interfaces and Outputs

• 7 UARTs for GPS, telemetry, digital video, receivers, ESC telemetry, and other devices.
• 8 PWM outputs, each usable for a motor or servo.
• 1 external I²C bus for magnetometers, airspeed sensors, and other devices.
• 1 external SPI bus for advanced expansion.
• 3 AUX GPIOs for custom functions.
• 2 ADC channels for voltage and current sensing.
• microSD for flight-log storage.
• SWD for low-level debugging and recovery.

Power and Mechanical Specifications

The flight controller provides regulated 5 V / 2.5 A and 12 V / 2.5 A outputs. The power input supports 3–6S batteries.

Dimensions and Installation

Installation recommendations:

1. Use 20 × 20 mm soft-rubber standoffs or another vibration-isolated mounting structure.
2. Install the board according to its arrow. If the board is rotated, configure the correct orientation in the firmware.
3. Keep GPS antennas, power cables, and digital video-transmitter antennas away from the IMU area.
4. Leave enough service clearance for the USB Type-C connector and microSD card slot.
5. Dual IMUs improve diagnostic capability but do not replace proper mechanical vibration isolation.

During the initial installation, take clear photos of the front and back of the flight controller and all wiring harnesses. These photos are useful later when checking connector orientation, wire order, or the hardware revision.

Interfaces and Power

Interface Definitions

Typical Wiring

Wiring principles:

• Connect a peripheral's TX to the flight controller's RX, and its RX to the flight controller's TX.
• Every serial peripheral must share a common ground with the flight controller.
• Connect the primary GPS to UART1 and an external magnetometer to the external I²C bus.
• Connect the DJI O3 to the dedicated UART3 interface, checking the 12 V pin and wire order before connection.
• Connect an SBUS or CRSF receiver to UART5.

NxtPX4v2 does not enable peripheral power outputs when powered only through USB. If the ground station can connect to the flight controller but cannot detect an external magnetometer or other peripheral, connect the main battery first and then reconnect USB for diagnosis.

Serial-Port Mapping

PWM Outputs

NxtPX4v2 provides 8 PWM outputs with the following hardware timer groups:

• M1–M8 support DShot.
• All 8 outputs support bidirectional DShot under ArduPilot.
• Channels in the same group should generally use compatible output protocols and frequencies.

Receiver

UART5 is the default RC interface and supports serial receivers using SBUS, CRSF, and similar protocols.

SBUS

• Connect the signal wire to the UART5 RC input.
• Use an appropriate power output from the flight controller and connect GND.
• ArduPilot uses SERIAL6_PROTOCOL=23 by default.
• PX4 can use RC_INPUT_PROTO=Auto for automatic detection.

CRSF / ELRS

CRSF / ELRS is a high-speed bidirectional protocol and requires both UART5 TX and RX.

If the receiver powers on but provides no channel data, first check the protocol, TX/RX direction, and serial-port mapping.

Battery Monitoring, Magnetometer, and I²C

Battery Monitoring

The ArduPilot firmware defaults are:

Current-sensor scaling can vary between power modules. Calibrate with a multimeter and a known load rather than copying factors from another flight controller.

External Magnetometer

The flight controller does not include a magnetometer. Connect an external magnetometer to I²C4:

• SCL → PD12
• SDA → PD13

External sensors may not receive power when the board is powered only through USB. If the magnetometer is not detected, connect the main battery to enable peripheral power, then connect USB and the ground station.

Flight-Controller Firmware

ArduPilot

• Official hardware target: NxtPX4v2
• Included in the official hardware support list starting with ArduPilot 4.6.0.
• Supports online firmware flashing through Mission Planner and MicoConfigurator.

Related links:

• ArduPilot NxtPX4v2 hardware definition
• Official ArduPilot firmware downloads
• ArduPilot Custom Firmware Builder

PX4

• PX4 board target: hkust_nxt-dual
• Bootloader target: hkust_nxt-dual_bootloader
• MicoConfigurator can flash PX4 firmware online in DFU mode.

Official PX4 firmware build guide

Build the default firmware from the PX4 source:

make hkust_nxt-dual

Build the bootloader:

make hkust_nxt-dual_bootloader

Related links:

• PX4-Autopilot
• QGroundControl
• NxtPX4 open-hardware repository

Troubleshooting

External Magnetometer Is Not Detected with USB Power Only

This is a common effect of the peripheral-power state. Connect the main battery first to enable the external 5 V / 12 V rails, then connect USB and the ground station and run detection again.

Related Resources

• NxtPX4 open-hardware repository
• Nxt-Dual hardware files
• ArduPilot NxtPX4v2 hardware definition
• PX4-Autopilot

Appendix A: Pinout Table