Hi there…
I want to get the pixhawk nuttx os …
how to build just Nuttx on ardupilot except copter firmware…
I guess it is possible add build option like 'px4-v3-nuttx’
but I don’t know how and where I do…
please guide me…
Not sure what you mean, the build by default is with Nuttx.
Just build the normal stuff like px4-v3 for example. And then grab the resulting Nuttx object files.
That is your operating system.