Hello!
The principle of microstepping is not very complicated (but the implementation can be).
Imagine one magnet and 2 perpendicular coils A, B.
If you power one coil at a time, you will have 4 positions depending on whether you power A and B
in one direction (+) or the other (-).
So if you write that on a piece of paper, A+ will turn your magnet for example towards the axis X+ (let's call
that 0 degree) then B+ will turn your magnet towards Y+ (90 degree) and similarily for X- (180) and Y- (270).
The switching sequence will be: A+, B+, A-, B-
I suppose you understand until here.
Now what happens if you power with the same current A and B? Your magnet will be oriented at 45
degree. The switching sequence will be: A+, (A+&B+), B+, (B+&A-), A-, etc.. and you will have 8
"microsteps" of 45 degrees each although your motor was designed for 4 steps of 90 degrees.
The same principle applies to any stepper motor. I explained half steps with equal currents, but if you
can control current accurately, you can also make quarter steps (make one current 3 times stronger as
the others, and you will have quarter steps). Then you can calculate what you should power for even
smaller steps.
Dora.