Was working.. Now communications errors.

Ok - my set up
Raspberry Pi 3 using the latest Image from the Repetier Server site.
Repetier server up and running ok
Printer is Tevo Black Widow connected to Pi using USB

I had loaded a job on to the Pi and told it to print. It got about 6% in and then started to run this to the log. Printing very slowly, about one move every 3 seconds

Can anyone help?
Many thanks

12:03:28.979: Warning: Communication timeout - resetting communication buffer.
12:03:28.980: Connection status: Buffered:94, Manual Commands: 1, Job Commands: 5000
12:03:28.980: Buffer used:94 Enforced free byte:41 lines stored:4
12:03:32.986: Warning: Communication timeout - resetting communication buffer.
12:03:32.986: Connection status: Buffered:110, Manual Commands: 2, Job Commands: 5000
12:03:32.986: Buffer used:110 Enforced free byte:41 lines stored:4
12:03:36.991: Warning: Communication timeout - resetting communication buffer.


  • Log is a bit incomplete, so I can only guess but looks like the back channel stopped working. So server got no "ok" and hence did not send new commands except on timeout since that means no "ok" but expected them so sending new ones.

    This serial-usb error does happen sometimes if power is not stable. Pi is very critical on it and it seems on some boards the counterpart as well. So if usb 5V gets 4.5 or maybe less for a short while it can cause such hangs. As a first test try a powered usb hup between pi and printer. pi power needs a 2.5-3A 5.1V power (yes better a bit more then 5.0 as it seems. Some power adapters are specially marked for pi to solve power problems). It is also the source of many instability problems.
  • Hi.
    I am using a certified Pi power pack and the printer is plugged in to the raspberry pis USB. No hub

    Many thanks
  • That is what I guessed. You power the printer over usb that is why an active hub can make a difference. But it is just a try. I also have them connected directly and no problems.
  • Ok.. But if the printer is powered on - then the arduino would not be drawing from the RPi...

    Anyway - I will do some more tests tomorrow.  Many thanks for all of the advice :)

  • Not sure about that. I think both - usb and main power then deliver power and if power fluctuates from main power e.g. because heated bed turns on this can drop voltage.

    A nice test with repetier-firmware is
    M111 S24
    which makes firmware just ack all gcodes. So you get no disturbance form all power sources and print is fast (not printing) and normally error free.

    If that works you could try
    M111 S14
    which is printing in dry run mode. Only stepper motors get power no heating. So light power usage. Full execution of all commands. Still normally no problems.

  • Many thanks for the above advice.
    It looks like it was a poor quality USB cable.  The above tests will be very helpful to dianose any other issues I am having exp with some of the mods I am doing to my printer.

    Again thanks for your help
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