42 Stepper Motor Driver Expansion Board DRV8825 A4988 3D Printer Control Shield Module

When I obtained the DiGiYes 42 Stepper Motor Driver Expansion Board, I did not realize it was an adapter to mount the A4988 driver.The board is well made, with a clear, crisp silkscreen to identify connection points and four thru-hole mounting points in each corner. All solder joints are perfectly done, and the leads are uniformly cut to length. The board is nicely cleaned with no flux residue.There is no documentation provided with the board, which would have been very helpful to understand how to plug in the A4988 board. There is no key on the A4988 sockets, and one could install it backward. Spending some time searching the internet did not provide any help on which way to plug in the A4988 board. The Expansion board socket has only a single pin marked on it, and it is marked Vin, which connects to the V pin of the A4988 card. See the attached picture showing the A4988 plugged in and its orientation to the Vin labeled pin of the Expansion board.The row of pins labeled S, V, and G have unknown functions, and I am still trying to understand how to connect the Expansion Board. A little documentation would go a long way to help, and I wish the seller had included that. The motor wires four-pin plug easily enough into the four-pin socket and is keyed so it can only plug in one way. There are convenient 12V power connections with screws to tighten the wires.It would have been very convenient if the Expansion board through holes in each corner matched the NEMA 17 motor body screws to be able to mount the driver there, but they dont, See the attached picture.Until I understand the connections, I have not powered up the unit and will update this review after I get the information and I am able to drive a motor.