What exactly does the Calibration do ?

Hi,

As I am using an Arduino Uno rather than a shield, I've re-written the Arduino FW to simplify it. I couldn't get my stepper motors to work with the AccelStepper class thats used in the MotorDriver.cpp arduino source. I have written a simple step function that takes moves the stepper one step.

Running the calibration routine seems to makea full turn of the motor first, then moves the chessboard on the stepper -128 steps repeatedly, meaning the stepper motor ends up going around another full turn or two. Is this correct ? Or is the calibration supposed to be moving it 128 steps clockwise, then 128 counter clockwise back to the starting position ? 

Any clue on what the calibaration operations are from the server ?

Thanks.