I have currently 10 Prusa printers (and growing) in my 3D printing farm, 7 are MK3 and 3 are MK3S.
One Prusa MK3 and one Prusa MK3S just won't connect to Raspberry Pi over serial port. I use same Raspberry Pi and same usb cable to connect to other 8 printer without problems.
Also boards and serial port on both "problematic" Prusa machines works ok when I connect to a laptop. I tried updating firmware to both "problematic" printers via two different laptops, one running Linux and other Windows, and this works without problem.
I can't figure out why these two have problems connecting to Raspberry Pi over serial, any ideas?
Does Prusa have different usb to serial chips on different boards? What could cause this?