For the USB controller and reversing the rotation for a motor, you would need to do this in the software (planet-cnc). In the configuration, you will need to reverse the direction by inverting the direction output.
Technically, the motor changes direction when the direction signal changes from a high to a low, or vice verse. For instance, the motor turns in one direction when the direction signal is, say, low. The motor will turn in the other direction when the direction signal is high. High is 5v and low is 0v or gnd.
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I have wired the step motors with the USB breakout board. When I jog the y axis it travels in the wrong direction. How do i switch the motors rotation?