More info on Xerxes VSD-E, from manual:
Status of stepping motor support
The stepping motor support in VSD-E firmware version 1.20 is
preliminary and intended for development use only.
Customers are recommended to wait for final stepper motor support before using VSD-E for steppers. When ready, the
upgrade will be freely downloadable from Granite Devices web site.
However, the firmware V1.20 is already able to control stepper as high pole count sinusoidal AC servo motor
(with encoder). This can be achieved by entering following configuration parameters in GDtool