The rate at which is steps is decided by the number of step pulses you supply to the unit not by the unit itself. It is possible that the unit could be reaching its upper limit at 40k+ pulses per second (I'm not really sure what the upper limit is to be honest, I'll have to check into that) but in that case it would be skipping steps and not just stepping slower. And I have no idea why the direction would have any bearing on it. Could it be a mechanical issue where the motor is closer to the edge of stalling when going backward?
I'll see what I can figure out. |