added commands

So I’ve added commands to support forward/backward stepping and upper and lower sides.

R for Read

D for Dump

F/B for stepping either Forward or Backward

U/L for selecting upper or lower side.

I’ve tested these commands and they are working.

Now it’s just a matter of putting everything together and having the software make the various requests in the right order.  Veneri’s software is pretty complete, and so what I’ll end up doing is just plugging my serial code into the appropriate places.  I guess I could just replace those functions which have to do with hardware with my code.  That would be the cleanest.