NxtPX4 V2 Mini Flight Controller — User Manual
The NxtPX4 V2 (board name: NxtPX4v2) is a 20×20 mm mini flight controller with full-size H7 performance, designed as open-source hardware by the HKUST UAV Group and manufactured by MicoAir. It was created for a specific audience: researchers and developers building small PX4 drones — VIO (visual-inertial odometry), swarm, and autonomy work — who need clean dual-IMU data, a hardware design they can inspect and modify, and a board that fits airframes where a 30.5×30.5 stack won't. It runs PX4 natively (hardware follows the PX4-V6 standard) and is also officially supported by ArduPilot.
Where to buy
- Robofusion store (ships from Canada — free Canada-wide shipping): NxtPX4 V2 Mini Flight Controller
Most FPV flight controllers are closed designs: you get the board, not the schematic. The NxtPX4 V2's full hardware design is public, which means a lab can verify signal paths, add custom sensors, or respin the board for a project — no reverse-engineering. Following the PX4-V6 hardware standard means mainline PX4 firmware runs without vendor patches, and future PX4 releases keep working. HKUST also maintains a modified branch that publishes IMU data to ROS at 500 Hz — exactly what VIO pipelines want.
NxtPX4 V2, H743 V2, or F405 V2 — which one?
| NxtPX4 V2 | H743 V2 | F405 V2 | |
|---|---|---|---|
| Processor | STM32H743, 480 MHz | STM32H743, 480 MHz | STM32F405, 168 MHz |
| IMU | BMI088 × 2 (dual) | BMI088 + BMI270 (dual) | BMI088 |
| Firmware | PX4 (native) / ArduPilot | ArduPilot / PX4 / INAV / Betaflight | ArduPilot / INAV |
| Mounting | 20 × 20 mm, Φ3 | 30.5 × 30.5 mm | 30.5 × 30.5 mm |
| Weight | 6.5 g | 10 g | 9 g |
| OSD chip | None (HD DisplayPort only) | AT7456E + DisplayPort | AT7456E + DisplayPort |
| Best for | Small PX4 research / VIO drones | Do-it-all flagship | Budget long-range |
Specifications
| Item | Specification |
|---|---|
| MCU | STM32H743VIH6, 480 MHz, 2 MB flash |
| IMU | 2× BMI088 (dual, independent) |
| Barometer | SPL06 |
| Logging | MicroSD card slot |
| Interfaces | 7× UART, 8× PWM, 1× I2C, 1× SPI, 1× SWD, 2× ADC |
| USB | Type-C |
| HD VTX connector | SH1.0-6P for DJI O3 Air Unit (DisplayPort) |
| BEC | 5 V 2.5 A (peripherals) + 12 V 2.5 A (VTX, camera) |
| Battery input | 2–6S LiPo, on-board voltage sensing |
| Compass | None built-in — connect external via I2C (SDA/SCL) |
| GPIOs | 3 on the AUX connector (ArduPilot pins 81/82/83) |
| Mounting | 20 × 20 mm, Φ3 mm holes |
| Dimensions / weight | 27 × 32 × 8 mm / 6.5 g |
| Hardware design | Open source (HKUST Nxt-FC), PX4-V6 standard |
Pinout
Front and back pad layout:
UART mapping
| Port | ArduPilot | PX4 | Default function |
|---|---|---|---|
| USB | SERIAL0 | — | GCS connection |
| UART2 | SERIAL1 | TELEM1 | MAVLink2 telemetry |
| UART4 | SERIAL2 | TELEM2 | MAVLink2 (companion computer) |
| UART1 | SERIAL3 | GPS1 | GPS |
| UART3 | SERIAL4 | GPS2 | DJI O3 (DisplayPort) |
| UART7 | SERIAL5 | TELEM3 | ESC telemetry (RX only) |
| UART5 | SERIAL6 | RC | RC receiver input |
| UART8 | SERIAL7 | SERIAL4 | Spare (user) |
All UARTs are DMA-enabled. Note the deliberate numbering: physical UART2/UART4 are the MAVLink telemetry ports — on a research drone, that's one for the radio and one for the onboard computer.
RC input
UART5 is the default RC port:
- SBUS — the SBUS pin (hardware-inverted into RX5) works out of the box; on PX4 set
RC_INPUT_PROTO = Auto - CRSF / ELRS — wire RX5 and TX5; on ArduPilot set
SERIAL6_OPTIONS = 0(telemetry comes back automatically) - FPort — TX5 with
SERIAL6_OPTIONS = 7; SRXL2 — TX5 withSERIAL6_OPTIONS = 4 - PPM is not supported
RC can also be moved to UART2, UART4 or UART8 (SERIALn_PROTOCOL = 23, and change SERIAL6_PROTOCOL away from 23).
HD VTX
The SH1.0-6P connector carries a DJI O3 Air Unit connection with DisplayPort OSD. There is no analog OSD chip on this board — it's designed for HD video or camera-less research airframes.
Pin 1 of the SH1.0-6P connector carries the 12 V BEC rail. Never wire a 5 V peripheral to it.
PWM outputs and DShot
8 PWM outputs, all supporting bi-directional DShot (ArduPilot). Outputs are grouped — same protocol within a group:
| Group | Outputs |
|---|---|
| 1 | 1, 2, 3, 4 |
| 2 | 5, 6 |
| 3 | 7, 8 |
Battery monitoring
Built-in voltage sensing (up to 6S); current sensing via an external sensor on the Curr pin (typically from a 4-in-1 ESC). Default ArduPilot parameters:
| Parameter | Value |
|---|---|
BATT_MONITOR | 4 |
BATT_VOLT_PIN | 4 |
BATT_CURR_PIN | 8 |
BATT_VOLT_MULT | 10.2 |
BATT_AMP_PERVLT | 20.4 |
Note the values differ from the 30.5-size boards — don't copy parameters across models.
Compass
No compass on board. For outdoor GPS flight, add a GPS+compass combo on the SDA/SCL pads. Indoor VIO-only research builds typically fly without one.
Firmware
| Firmware | Support | Target / notes |
|---|---|---|
| PX4 | Native | Build targets hkust_nxt-dual (bootloader: hkust_nxt-dual_bootloader); 500 Hz IMU ROS branch from HKUST |
| ArduPilot | Official | Target NxtPX4v2 — builds on firmware.ardupilot.org |
First-time flashing (DFU)
- Hold the bootloader button, plug in USB — the board enumerates in DFU mode
- Flash the
*_with_bl.hexfirmware with your DFU tool - Afterwards, update with
.apjfiles (ArduPilot) or via QGroundControl (PX4) over plain USB
FAQ
Is this board only for researchers?
No — it's also a solid pick for any small ArduPilot/PX4 build where 20×20 mounting and 6.5 g matter. But its distinctive features (open hardware, PX4-V6 compliance, 500 Hz IMU ROS topic) are aimed at autonomy work; if you just want a general-purpose FC, the H743 V2 gives you more UARTs, analog OSD and Bluetooth for similar money.
How do I connect a companion computer (Jetson / Pi)?
Wire the companion's UART to UART4 (TELEM2 on PX4) and set it up as a MAVLink port — the standard PX4 offboard-control path. UART2 stays free for a telemetry radio like the LR900.
Can it fly FPV with analog video?
Not directly — there's no analog OSD chip. Pair it with an HD system (DJI O3) via the HD VTX connector, or add an external OSD. For analog-first builds, choose the F405 V2 or H743 V2.
Related guides
- H743 V2 Flight Controller — User Manual
- F405 V2 Flight Controller — User Manual
- PX4 — Telemetry Setup Guide
- ArduPilot — Telemetry Setup Guide
Written and maintained by the Robofusion engineering team. Hardware reference data from MicoAir Tech, HKUST UAV Group, and the ArduPilot documentation (CC BY-SA 3.0).