# PX4 参考飞行控制器设计

PX4 参考设计是飞行控制器的 Pixhawk 系列 。 该设计于2011年首次发布,现已进入第5 (第六代电路板设计正在进行中)。

# 二进制兼容性

所有按照特定设计制造的主板预计与二进制兼容(即可以运行相同的固件)。 从2018年起,我们将提供一个二进制兼容性测试套件,使我们能够验证兼容性。

第1-3代 FMU 设计用于开源硬件,但到了第4-5代只提供 pin 输出引脚和供电规格(原理图由个人开发者生成)。 为了可以更好的确保兼容性,FMUv6 及更新的版本重新提供完整的设计模型。

# 参考设计迭代:

  • FMUv1:开发板 \(STM32F407, 128 KB RAM, 1MB flash, 原理图 (opens new window)\)(PX4 不再支持)
  • FMUv2:Pixhawk \(STM32F427, 168 MHz, 192 KB RAM, 1MB flash, 原理图 (opens new window)\)
  • FMUv3:2MB Flash 的 Pixhawk 变种 \(3DR Pixhawk 2 \(Solo\), Hex Pixhawk 2.1,Holybro Pixfalcon,3DR Pixhawk Mini,STM32F427,168 MHz,256 KB RAM,2 MB flash,原理图 (opens new window)\)
  • FMUv4:Pixracer \(STM32F427, 168 MHz, 256 KB RAM, 2MB flash, 原理图 (opens new window)\)
  • FMUv4 PRO: Drotek Pixhawk 3 PRO (STM32F469, 180 MHz, 384 KB RAM, 2 MB flash, 输出引脚 (opens new window))
  • FMUv5: Holybro Pixhawk 4 (STM32F765, 216 MHz, 512 KB RAM, 2 MB flash, 输出引脚 (opens new window))
  • FMUv6:尚未完成,最终命名为 TBD,变种 6s (STM32H7, 400 MHz, 2 MB RAM, 2 MB flash) 和变种 6i (i.MX RT1050, 600 MHz, 512 KB RAM, 外部 flash)

# Main/IO Function Breakdown

The diagram below shows the division of bus and functional responsibilities between the FMU and I/O boards in a Pixhawk-series flight controller (the boards are incorporated into a single physical module).

PX4 Main/IO Functional Breakdown

Some Pixhawk-series controllers are built without the I/O board in order to reduce space or complexity, or to better address certain board use-cases.

The I/O board is disabled by setting parameter SYS_USE_IO=0. When the I/O board is disabled:

  • The MAIN mixer file is loaded into the FMU (so the "MAIN" outputs listed in the Airframe Reference appear on the port labeled AUX). The AUX mixer file isn't loaded, so outputs defined in this file are not used.
  • RC input goes directly to the FMU rather than via the IO board.

Flight controllers without an I/O board have MAIN ports, but they do not have AUX ports. Consequently they can only be used in airframes that do not use AUX ports, or that only use them for non-essential purposes (e.g. RC passthrough). They can be used for most multicopters and fully autonomous vehicles (without a safety pilot using RC control), as these typically only use MAIN ports for motors/essential controls.


Flight controllers without an I/O board cannot be used in airframes that map any AUX ports to essential flight controls or motors (as they have no AUX ports).


Manufacturer flight controller variants without an I/O board are often named as a "diminutive" of a version that includes the I/O board: e.g. Pixhawk 4 Mini_, CUAV v5 nano.

Most PX4 PWM outputs are mapped to either MAIN or AUX ports in mixers. A few specific cases, including camera triggering and Dshot ESCs, are directly mapped to the FMU pins (i.e. they will output to either MAIN or AUX, depending on whether or not the flight controller has an I/O board).