Its possible I’m exceeding the capacity of the on-board 12v power. My calculated consumption is between 800mA to 1.3A (depending on number of active outputs). I might be right at the 1A limit during normal operation — I’ll have to check that out (P.S. I sent you the databus info via email). Would exceeding the capacity cause the symptom that I’m seeing? An I\O expander going “missing” on a data bus line? What’s odd is that its always the same expander every time. I would expect a power issue to be more systemic and cause random dropouts, if not across the board, then at least on the same databus branch.