Well, building things like a Sumpod can be loads of fun!  You may have noticed that the LCD was working in the last post, which it was… and the problem?  Well, I did wire it all quite correctly, but after getting nothing but a line of fully filled in blocks, I decided to go deeper.  Now understand that everything else was working fine — all 4 motors and the control for the extruder heater responded perfectly.

The problem, as it turned out, was that two of the auxilliary digital lines used for the LCD were not actually connected to the corresponding pins on the arduino board!  The RAMPS board had two lines where running continuity checks proved out that those connections were open!  The traces are on the edge of the board and the connector are short, but the copper between them was open.  I easily fixed this with some #30 wirewrap wire to directly connect the output pin to the corresponding pin going to the arduino.  If you look very closely at the picture, you will see the wires from the second and fifth pins going from the dual row header to the edge connector. I’ve built many hundreds of printed circuit boards in all sorts of projects, and this does sometimes happen to multilayer boards.

Of course, for me this was just the “luck of the draw” in as much as there is no way, short of building the board, to discover this, unless the board manufacturer did a full circuit test.  Once patched, the LCD works everytime!