Hi Tom, many thanks for your detailed explanation on drivers connections, now it's perfectly clear to me how to use them. Another doubt has arisen to me about powering the Mega board. Currently I have only one connection from the PC to the board that is the USB cable, for both power and data transmission (the steppers are powered from a dedicated 12V line). In the schematics the power to the board is supplied by a 12V external source via VIN pin but how the data transmission is being achieved? As far as I know it is not recommended to connect an USB cable togheter with an external power source to the Mega2560.
Gigi