badger писал(а): Is the A axis not needed to drive the stepper to do rotation?
You do not need to use it as an separate axis. If you define A axis, LinuxCNC will control it, including give commands and check for the feed-back to check Following Error.
If you do not define this axis inside ini, LinuxCNC will not know anything about it.
stepgen - the component that controls steppers works separately from LinuxCNC motion (main motion control component). Basically it takes (this defined in hal)
axis.N.postion-cmd and gives back a Feedback to axis.N.postion-fb.
You can give commands to stepgen yourself. In fact you are already doing it .
badger писал(а):If atan2 can rotate the needle without it being "A axis"
yes it can.