Just got Octoprint downloaded to my Raspberry 3B+ and its working fine, only issue is that when I shut my Ender 3 Pro off the display on the printer is still on as long as I have the usb connection between the printer and Raspberry? Soon as I disconnect the cable the display shuts off?? Somehow the display is pulling power from the Raspberry through the USB cable with the printer turn off and even unplugged from AC power?
Hi I have the same printer and it does the same.
Here is my 2 cents
The RPi is sourcing 5 volts out it's USB port to the printer's controller board which in turn is keeping it semi alive. IMHO, Creality/Ender should not have directly connected the USB 5 volt line to the internal 5 Volt power bus. This is a printer which is a "device" and it does not need the 5 volts from the "host". It is up to the "device" to handle this. The "host" ( normally a computer) has no idea what "device" you are going to plug in to it so it sources the 5 volts on it's USB ports for peripherals like mice. keyboard. hard drive. etc that do require power. A printer is a "device" but it does not require this USB power therefore it should isolate it or have it selectable if there is a need for the printer to act as a "host". Not trying to knock Creality just taking the time to explain this as it is a pretty common issue in the USB world that a lot of designers over look, not just printers.
So the simple and easy method is the tape trick to isolate the 5 volts.