Calculate the correct current limit for driver A4988

[MicroBahner]

@acroscene

However I had to lower the speed a lot to make it run at 6 volt. But it is not very smooth going CCW. Since it is goes a bit jaggy it struggles to keep its position as well.

What voltage did you apply to the motor before? Maybe you damaged it already. This little 5V steppers cannot withstand higher voltages for long.