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Hello everyone,

I had my printer working fine a week or so ago and when I went to start it and run it yesterday, I kept getting an error saying that the COM port was taken and access was denied. I received the same error from Repetier-Host and Arduino. So I am doubting that the software is the issue.

I have the driver installed from the RAMBo wikipedia page. Under my device manager, it is showing the device as RAMBo, so I believe that is fine.

I thought maybe the USB connection on the RAMBo board was broken so I tried wiggling it and eventually was able to connect it after holding it some weird way and disconnecting and reconnecting it, I got it to connect. So after this, I thought I was going to have to solder it back on. I disconnected all the wires and removed the RAMBo. To confirm that the connection was the issue, I plugged the cable in and tried to connect to it. However, this time I was unable to connect even with wiggling the cord and such. I probed the four solder joints on the RAMBo board where the USB connection leads. Vcc and Ground were reading ~5V, even with wiggling the cord. The data lines were also reading a voltage ~3.33V, but I don't have an oscilloscope to actually test if these are transmitting data correctly. Therefore, I am kinda doubting that it may be a bad connection.

I also tried a different cable, specifically the one that I use for my printer, and I had the same issue.

Do you guys have any more ideas on how to diagnose this issue? My next plan of action is to try a different computer.

To quote from "The IT Crowd": Have you tried turning it (the computer) off and turning it back on again?

Usually that error occurs, not because of a dodgy connection, but because some software has opened the COM port in Windoze and not released it. Usually it's the host software that hasn't shut down properly, left the port locked and Windoze is too damned stoopid to close a process's resources when the process dies. When this happens, bouncing the power on the computer is your only way out.

If that doesn't work I think you're on the right track: try from another computer. That'll at least point at whether it's the RAMBo or the computer (as you've now eliminated the cable as a problem).

Whenever the device software was installed, I had to restart my computer. So I did try that and it did not help.

However, I have fixed the issue. I downloaded the new version of Repetier-Host, and with that Repetier Server. The server was running in the background and blocking the COM port. So once I stopped the server, this solved the issue.

addisonElliott wrote:Whenever the device software was installed, I had to restart my computer. So I did try that and it did not help.

However, I have fixed the issue. I downloaded the new version of Repetier-Host, and with that Repetier Server. The server was running in the background and blocking the COM port. So once I stopped the server, this solved the issue.

Great for finding the problem! Those can be a bear to find. Good Job!

Same thing happened to me. Fixed it like you did.

For you hardcore windows users ( yea yea laugh it up), open a PowerShell and copy/paste this command to see available COM ports.
You can close/open ports as-well, but it might be easier to just restart

https://msdn.microsoft.com/en-us/librar ... .110).aspx