I use a complete pc-based motion-control which generates step / direction outputs. For controlling small dc-motors with attached encoders, I need a small interface, which counts the steps from the MoCo-System on one hand and the encoder steps from the motor on the other hand to generate an analogue or digital reference output. The motors need to be positioned precisely. The interface may be a stand-alone part or a complete unit together with a motor driver. Because I already have the pc hard- and software I do not want another part which have to be build into the computer. The interface should be not too complex (and too expensive). Does anyone have an idea what solution is possible?