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  1. #1
    3D Printer Noob
    Join Date
    May 2019
    Post Thanks / Like

    losing usb connection (bad mains power?)

    I have a CR-10 and an Ender 3. Both have worked fine for months with latest raspi Octoprints.

    I recently added AC bed heaters. They really heat up fast and high and they draw a lot of power. I've printed a number of small prints with them. I've also built styrofoam enclosures for both of them but they only get up to about 45 degrees C inside. (The electronics are in the enclosures but 45 should be no problem.

    The other day I started a long print on each printer and during the night both failed with the exact same octoprint error at the exact same time. This is the error from the octoprint log.

    019-05-29 21:36:36,295 - octoprint.util.comm - ERROR - Unexpected error while reading from serial port
    Traceback (most recent call last):
    File "/home/pi/oprint/local/lib/python2.7/site-packages/octoprint/util/", line 2605, in _readline
    ret = self._serial.readline()
    File "/home/pi/oprint/local/lib/python2.7/site-packages/octoprint/util/", line 4681, in readline
    c =
    File "/home/pi/oprint/local/lib/python2.7/site-packages/serial/", line 501, in read
    'device reports readiness to read but returned no data '
    SerialException: device reports readiness to read but returned no data (device disconnected or multiple access on port?)
    2019-05-29 21:36:36,328 - octoprint.util.comm - ERROR - Please see for possible reasons of this.
    2019-05-29 21:36:36,357 - octoprint.util.comm - INFO - Changing monitoring state from "Printing" to "Offline (Error: SerialException: 'device reports readiness to read but returned no data (device disconnected or multiple access on port?)' @"
    2019-05-29 21:36:36,480 - octoprint.plugins.DisplayLayerProgress - INFO - Printing stopped. Detailed progress stopped.

    I'm guessing the printers rebooted but I don't know how to find out if they did. It is not like the printers have logs. Is there some way to monitor a printer's health and log it in octoprint?

    This has happened again to each printer but not at the same time like the first incident.

    The only thing I can think of that is in common is the 110 VAC mains coming into the printers. This is in an old garage that probably has crappy wiring.

    So I bought a good 500W battery-backup UPS (uninterruptible power supply). I only plugged the printers and raspis into the UPS and left everything else, including the bed heaters, plugged into the wall.

    I started prints on both printers and within 10 minutes one got the error again. I'm returning the UPS.

    I'm desperate since I can't print and my job depends on it. Any ideas would be greatly appreciated.

  2. #2
    Super Moderator
    Join Date
    Nov 2016
    Post Thanks / Like
    Looks like something is not handshaking properly anymore. Could something have changed is communication speed or protocol?



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