If I set D0 high and all others low, the motor takes one position. Then if I set D1 high and all others low, the motor rotates to next whole step. But if I leave D0 at high while D1 goes high, the motor takes the half step inbetween. What prevents from introducing microstepping here? Can't D1 go halfway high? Or is 5 wire unipolar so ancient technique that nobody bothers to develop microstepping drivers for them?