Quote Originally Posted by antsals View Post
What is opto-isolation?
Instead of there being a direct electrical connection between the computer and the driver the connection is effectively split with light bridging the gap. The opto-isolator uses an LED and a phototransitor to sense the light. If there is a high voltage on the motor side of the board it cannot reach the other side since there is a physical gap (within reason).

Google it...

You could get round the 'problem' of having both the driver and interface board isolated by buffering it - few logic gates, maybe not even that. Or even pop open the driver and bypass the isolation with a bit of wire! Kind of defeats the object of buying it ready made though, and you're increasing propagation delay which may/may not be significant.