PI Server Looses Connection & Print Stops

Raspberry Pi server is connected to Ender 3 running latest Merlin.  Print suddenly stops.  Pi screen shows no connection to printer, that is printer commands are blanked!  Temperature of bed and nozzle stay high so I think it unlikely to be a power glitch.

Of course this only happens 10 hours into a 12 hour print :) but it has happened several times.

Any thoughts?  Thanks


  • Where do you see temperatures? On printer lcd oder pi screen? Because pi screen should not show any if it thinks it is disconnected and would also reconnect if possible. I ask because a known problem is when linux does not disconnect serial but communication stops working due to some problem in associated components. Then you just see timeout in console appearing from time to time and nothing happens. That would then be an error introduced from electronic noise/voltage drops.

    The other frequent reason is that the pi disconnects usb due to undervoltage. Enter in ssh shell
    after some time to see if you are prone of the problem. Not every message of it kills usb but it might happen. In that case server would reconnect but print is then stopped. With enabled rescue handling you could then continue the print in many cases.
  • Temp is seen on printer LCD.  Pi does not show anything about printer.

    Your comments about power could make sense, particularly if Pi is more sensitive than printer.   I'm now running these long overnight jobs from SD card and have no problems.   I'm thinking of "borrowing" my computer's UPS for a few days.

  • Ok, then it is the crash of usb communication while linux keeps the serial open. Nothing that can be done here software side as it is a hardware problem. Check on pi with
    if you see undervoltage messages after a while running. Would be an hint that it is the pi power. But can also be noise on usb cable (use shielded cable) or even 5V on printer board. Often good pi power also stabelizes this as well. For pi make sure it is a power supply and not a usb charger. USB chargers are too slow in voltage adjustments in most cases.
  • Its a good supply that came with the Pi.  Also I now have a UPS so there should be no problem with mains power.
  • Only thing counts is that "dmesg" does not show undervoltage warnings after a few hours or running. UPS is normally no help except if main power is unstable at your location.
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