Since ArduPilot builds on top of the PX4 flight stack, does SERVO1_FUNCTION map to a PX4 parameter?

No, AFAIK there is no direct replacement in the PX4 autopilot software.

Ardupilot runs to top of four different operating systems:

  • Nuttx (aka PX4)
  • Linux
  • F4_light
  • ChibiOS

ChibiOS will probably be the operating system of choice in the near future.
You can already downlod binaries for a big range of boards from

@amilcarlucas Nuttx is just the RTOS used by flight controllers like the Pixhawk or Pixracer to run the firmware code (aka PX4 or ArduPilot). What I meant with ArduPilot builds on top of the PX4 flight stack, I meant the firmware code not the OS where the code runs. Thanks for the info about ChibiOS though.

Maybe @tridge or @priseborough knows how that SERVO1_FUNCTION parameter from the AP_.cpp module links to the PX4 firmware CPP module.

SERVO1_FUNCTION is implemented in ardupilot code, using minimal stuff from the PX4 firmware layer.

So I do not think there is a map to a PX4 flightstack parameter