Printing files over USB drive (Ender 3 Pro) Is this possible? I know that the controller board of the printer is normally controlled (when using USB) by an active computer sending data, but I was wondering if it could be reversed so that the board retrieves files from a USB flash drive? My SD card keeps failing and is overall frustrating to work with, so USB would be a nice option.
Unfortunately, no.
There are two types of USB devices: host, such as a PC, and device, such as a thumb drive. (Actually, there is a third type, on-the-go, which can act as either.)
The Ender 3 mainboard is a USB device which means that it can only connect to a USB host. You cannot directly connect two USB devices, such as the Ender 3 and a thumb drive) and have them work.
One option would be to set up OctoPrint software on a Raspberry PI single-board computer and connect that by USB to the printer.