The diagram (on which I can only see the X axis limit, appears to have four wires to it. Yellow and black for the power, and the return is via the black and brown. I assume the second black wire is also at Ov potential as a reference for the brown wire. You do, however need some reference across to your breakout board for this to "spot" the voltages coming out.Unless you are using the rest of the board for some other purpose, I would do away with it. Power the switches directly from your 5 vlt/0v supply on your nreak out board, and take the return directly in.