I'm tempted to junk the display and try another, but before I do that can anyone offer any suggestions as to what might be wrong?
BillThank you for your very helpful reply.I have traced out the wiring of my adapter board as best I can, and entered the mappings into the constructor. This produced more promising results, in that both lines of the display now show up. However, whatever I try to print and wherever I try to print, unexpected symbols (typically "0"s and arrows) show up, often in the first or last display positions (depending which way is "up" for the display). And once the sketch has uploaded it makes no difference to the display if the I2C lines are unplugged, so clearly the Uno is playing no further part in the proceedings! It's getting late here now, so I'll leave it until tomorrow and explore some more then.Where can I find your "guesser" sketch? It didn't seem to be in any of the threads you linked.Mike