Working great until I add some more USB connections (Pi)

I have server running on a pi 3b+ with a usb hub (powered) connected to 2 printers and 2 logitech c270 cameras. Also have a 7 inch touch lcd connected. I have a couple of issues:
  • All seems to be good except that on reboot it seems to swap usbs around and so I must remember to check the printers before sending prints to the wrong ones. Any way to fix this?
  • Adding two more usb cables (either in hub or straight into pi), these are 5 meter cables with the electronics in apparently to work with the extra distance, seems to cause the server to sort of freeze - lcd does not respond, prints stop and no comms to printers. Reboot using the menu brings it all back so not completely frozen (from what I can remember). Only have another logitech webcam connected to the new cables at this point, still building the Prusa. Happens everytime. I am going to check the hub psu just in case but otherwise any ideas?


  • Hub psu is fine. PLease can someone give me an idea how to track this? Web side is still working but no comms to any of the printers, so no response etc. Thanks
  • Linux has 3 paths for same device. Directly in /dev they are numbered in order of detection, so a bit random. Then you have /dev/serial/by-path or by-id. If they have different ids select by-id otherwise select by-path version and remember the port connected. Then it will always get assigned the same way around.

    PIs are always quite sensible on usb signals and voltage drops, so having multiple devices can easily cause problems with it. The active hub should help here if it has enough power. Over ssh run

    sudo dmesg 

    and see if oyu get undervoltage messages like this:

    2428924.651708] rpi_firmware_get_throttled: 17 callbacks suppressed

    [2428924.651714] Voltage normalised (0x00000000)

    [2428932.971643] Voltage normalised (0x00000000)

    [2428951.691594] Voltage normalised (0x00000000)

    [2429163.851612] rpi_firmware_get_throttled: 18 callbacks suppressed

    [2429163.851620] Under-voltage detected! (0x00050005)

    [2429188.811617] Under-voltage detected! (0x00050005)

    [2429199.211604] Under-voltage detected! (0x00050005)

    [2429238.731794] rpi_firmware_get_throttled: 20 callbacks suppressed

    [2429238.731801] Voltage normalised (0x00000000)

    [2429247.051754] Voltage normalised (0x00000000)

    [2429253.291636] Voltage normalised (0x00000000)

    [2429471.691635] rpi_firmware_get_throttled: 16 callbacks suppressed

    [2429471.691643] Under-voltage detected! (0x00050005)

    [2429486.251660] Under-voltage detected! (0x00050005)

    [2429515.371649] Under-voltage detected! (0x00050005)

    [2429559.051712] rpi_firmware_get_throttled: 13 callbacks suppressed

    I also get them without problems, but as some point linux will disable usb which I gladly do not reach.

    Long cables are not officially allowed for usb I think, also I know often they work. Might also depend on isolation against external signals. Hard to say since you do not see where problems come from.

    Try first without webcams. The logitech should support MJPG so not add much bandwidth on usb but the usb bandwidth is limited, so first printers and if they work add cam one by one and no net select HD resolution. Pi is not the best device regarding band width. All share same usb port I think.

  • Thanks. I am printing at the moment so this will be a tomorrow evening investigation. I have left the long cables in and pulled the hub with the two printers on to use the prusa and all seems to be working ok. I am assuming its something to do with power. I am going to also try and get another powered hub to test tomorrow as well. Trying to prove it all works before buying the license for repetier. I think my trial runs out on Thursday. 
  • After trial it is still working as free version just without webcams but they are running. So if you solve it for free it will work with pro the same.
  • So managed to get it to freeze. No messages worth mentioning at all. Going to try leaving cameras off for a while and see if I can still reproduce it

  • I was about to run it on my windows server until while configuring I realised I had all the hassle with the webcams . But it is there now if I decide to use it (with all the drivers etc). But Looks like it may be fixed on my pi :). I think rather than a power issue it may be related to bandwidth over the usb, although I don't know why all the usbs would lock up including the touchscreen (I am not very familiar with the pi). It was ok running 3 printers (only 2 actually printing, but communicating with the other) and two cameras, so I reduced the camera settings down to 640x480 from 800x600 and have run 3 cameras and two printers printing with no lockups for 4 hours or more. I could not run the 3rd printer due to a clog :(. I do need to test for longer (with cameras) before buying but provided I can get enough test time in I will be buying it. Great work and will make my printing life so much better than having 3 octopi instances.
  • Make sure all webcams use mjpg compression. Experience shows that only one webcam without it uses most of usb band width. So for 3 it it important they also use mjpg. But as you see band width for pi is a bit limited. Try 1 or 2 webcams not over hub but directly. That uses hopefully a different usb channel with own limits. Not sure if this is the case for the pi but worth a try.
  • Thanks for your help. All is working using the hub for everything now (just the way I wired it last time). Cameras at 640x480 and now no problems running 3 printers and 3 cameras.
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