So I have my printer connected and running on Octoprint on a Raspi 3 running Octopi, and I couldn't be happier.
Except for one thing.
The arduino attempts to draw power from the raspi over USB, even when the main 12v PSU is off. This is not enough to power the SmartLCD, but it does mean that if the PSU is off and the raspi is connected, and then the PSU is turned on, the smartLCD displays bars and gibberish. I plan to eventually have a remote on/off switch for the PSU so that the Raspi is the only thing that has to stay on, but I'm afraid that leaving it connected to the printer over USB will cause issues.
Does anyone know of a way to establish a serial connection with the PICA/Mega combo that doesn't power the Mega? Do I need separate power supplies?