Ideally, plugging in the ESP Dev board with an SD Card module would look and function just like a USB Memory Stick.
Then every XX minutes, the ESP would read that same SD and preform functions if there have been any changes to the directory.
Many other closed threads here say this is not possible.
But it appears to be done here for a 3D Printer application using the ESP8266.
(note: the card in this case is being read by a 3d printer. but this would not appear to be any different than being written or read by a PC) The ESP would not be writing to the SD. Just reading on a timed basis.
In a perfect world with code to detect whether the CD was being accessed by the PC.
Is this physically impossible, or just difficult due to the danger (that code might solve) of simultaneous access?