Why is it that if I execute a gcode command that causes the stepper motor to turn in reverse (any negative move on the X axis), after the step it will emit a high pitched whine until it gets another command to rotate in its forward direction?
Executing multiple reverse commands will cause the tone to vary in frequency each step, and always it goes away after another step in the opposite (forward) direction.
And other times it does it in both directions, but only on every other step. One step +X its there, next step its gone, next step its back, and so on...
Then they also make a different noise when idle, before I disable them with the "disable steppers" command.
What are these noises?
And is it bad to leave the motors in this state? Will it burn them out?