See https://github.com/rusefi/rusefi/wiki/Custom-Firmware
firmware/hardware/board_hw_test.cpp
shows how to provide board-specific output metadata through board_overrides.h.
Add your output pins to OUTPUTS, update its array size, and set the DC motor
output count. The example defaults to zero outputs.
Keep the callback functions static and assign them to the corresponding
custom_board_getMeta* slots in setupBoardHardwareTestOverrides().
board_configuration.cpp calls this setup function
from setup_custom_board_overrides(). Upstream owns the public
getBoardMeta*() functions; defining those functions in a board causes duplicate
symbols at link time.
Upstream treats all listed outputs as low-side outputs by default. Boards that
need a different count can also register custom_board_getMetaLowSideOutputsCount.