Warning: connection timeout with Repetier server

I just moved to a Windows 10 laptop from a macbook. I installed repetier host and server onto my new computer, but neither the host or server can communicate with the printer.

When I connect with Repetier Server I immediately get "Warning: Communication timeout - resetting communication buffer".

Here is a screenshot of the log, you can see I enter G28 through repetier server but it took forever to show up in the log and then I get the timeout warning.
I've attempted to reinstall/update USB drivers a bunch, but it works fine with my macbook.

What is strange is that when I attempt to connect through serial connection rather than the server, it says no start signal detected and immediately crashes. Here I'm using the same settings as on my Macbook so I'm 99% sure the baud rate etc. is correct. 

I was able to connect and control my printer only when using a repetier software version that had the "reset on connect: disable" option, but this is a old version and I want to use repetier server.

Please help! I would really love to be able to use repetier host and server on my new computer :(

Thank you !!!


  • What board are you using? So far all my tested boards worked fine, so that we could remove that option. We now always go back to initial DTR/RTS setting. Printers not supporting this just ignore it as far as I know, but you never know.
  • A Melzi Board - SKU: 6007

  • Ok, might be a fake FTDI chip. Read this
    for more information about this problem and solutions.
  • Hi Repetier, thanks for taking the time to look into this and help me! But I do not think that is the problem. I've uninstalled and reinstalled the driver software a bunch of times and it doesn't seem to change anything. 

    The first sentence in the thread for fixes is "If, when you plug your Melzi in, it is recognised as an 'FT232R USB UART' in 'other devices' in the Device Manager..." and mine reads USB Serial Port (COM3) in my device manager. 

    Is there anything else I can try? When I try to connect to Repetier server it connects, but gives me 'Warning: connection timeout - resetting communication buffer'


  • If you have set a standard baud rate like 115200 baud connect using a serial terminal (e.g. monitor button in Arduino IDE). YOu should see some output from firmware and can even send commands. If this works and no wrong characters are present (from ftdi driver) then it should work with same baudrate in server. It is the same as a serial terminal program just with error checking etc.
  • Hi there,
    I have experienced the "time out" issue several times and I started investigating on the root cause.
    My printer is in the garage and it is connected to a laptop with 1 m USB cable, I use a Rumba board on a Prusa printer.
    I noted that the issue occurs 99% of the times within few seconds from when I go and check the printing progresses.
    This sounded strange to me. If I leave the printer alone nothing happens. If I go and check it, then I experience the time out!
    After weeks of thinking I finally was able to reproduce the issue causing the time out error.
    In my case the "time out" error occurs when I switch on the garage lights. There is one big fluorescent light on top of the printer at approx. 1.6 m. When I switch the light on, most of the times the printer goes in "time out" error.
    So obviously this has to do with some electromagnetic interference.
    I further investigate the issue and also noted that the solar inverter also in the same area (1.3 m away from the printer) does not cause any issue when switching on/off. It is only the fluorescent lights on switch-on that cause the problem. The new generation florescent ballasts operate between 20 kHz to 60 kHz producing strong electromagnetic interferences. I am sure there are also other origins causing this issue but at least I have been able to reproduce one of them which I hope will be of help for the community. I have not eliminated my root cause yet but now that I not it I will work on the grounding of the ballast and on the USB cable quality. Eventually I will move the printer somewhere else.
    I hope this helps other folks.

  • These lights seem to be a root of trouble. You are lucky that you only get a timeout. Many get a firmware reset from it. I think it is the starter that puts too much whatever on your local electric net causing some fluctuations. A typical solution is using a USV with battery to filter these effects.
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