I am using Arduino mega/Ramps 1.4/Marlin and am going to give the DRV8825 drivers a shot in place of the 4988's. Info on the 8825 via Pololus site reads- "The timing requirements for minimum pulse durations on the STEP pin are different for the two drivers. With the DRV8825, the high and low STEP pulses must each be at least 1.9 us; they can be as short as 1 us when using the A4988.". I m not having any luck locating this setting in Marlin. Anyone know?