Picks wrong printer

Hi, Im running Repetier-Server pro on a Raspberry Pi. I have 2 printers hooked up and they both run fine. A Crealty Ender 3V2 and an Elegoo Neptune 3 Plus. I don't always use both printers so if I turn on just the Neptune, Repetier says I turned on the Ender. If I unplug the Ender, it will switch to the Neptune but why would it be doing that? They are on 2 separate usb ports.


  • The devices /dev/ttyUSB0 etc are dynamic and can swap between the different USB ports depending on when they start up.

    Use the /dev/serial/by-path/platform......... devices.  These will always point to the correct USB port.

    Use dmesg to watch for when the USB port is plugged in and what port was configured

    [   11.508708] ch341 1-1.2:1.0: ch341-uart converter detected
    [   11.560645] usb 1-1.2: ch341-uart converter now attached to ttyUSB0

    The translates to /dev/serial/by-path/platform-fd500000.pcie-pci-0000:01:00.0-usb-0:1.2:1.0-port0 on my PI.  Yes these are symbolic links to the ttyUSB device, but the system maintains the links to ensure that the device points to the correct device.
  • Yikes!  :) I'm afraid I'm missing something here. Can you explain how I do this?
  • Port names in /dev depend on activation order and you likely have selected /dev/ttyUSB0 or similar in that folder. So depending on order you activate printers it is randomly correct or not. 

    Use insted in connection settings a port name that starts with /dev/serial/by-path/... and the usb port you connect it to is used to determine which printer gets connected and no random association any more.
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