I need some advice as I have tried everything I know to no avail. I connect 1 1602a lcd as per instructions on web site and it works perfectly. I connect the 2nd lcd and only partial data shows. Now some of the data on the first lcd is incorrect. When I remove the second lcd the first is again correct. I have switched lcds and the same thing happens.
I have a 2 amp power supply for the Arduino 2560 and powering the backlits with a separate USB power.
I don't know what else to do and have been trying different things for weeks. I need some ideas.