I'm new to Arduinos but researched thoroughly before buying one. Just for context I'm an IT Professional with 20 years in the game, I'm comfortable with Linux/Unix, Windows, Raspberry Pi's, electronics, hardware, software and monitoring/switching COM ports.

I've purchased my first Arduino (actually a Elegoo Uno R3 clone) and have just tried it out of the box connected to two different systems; one Windows 7 64bit Enterprise the other Kubuntu. Despite having the correct COM port selected on both I'm getting similar error messages:

**avrdude: ser_open(): can't open device "\\.\COM15": The system cannot find the file specified.**


**avrdude: ser_open(): can't open device "\\.\COM6": Access is denied.**

Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

Yes I have tried different COM ports.

Yes I have tried turning off Firewalls

Yes I have tried different USB cables.

I have a solid green LED and a intermittently blinking orange LED.

The suggested Troubleshooting guide + many Forum Threads do not seem to cover this exact error I'm encountering - well they do but they tend to be people with the simple issue of them not selecting the correct COM port or having the same COM port tied up with another task. Then choose the correct port and it works. I'm confident I have the correct COM port and when I click Get Board Info it pulls down the correct board information and serial number etc.

On the Linux system I was seeing a similar behavior with slightly different wording: Permission Denied

On my Windows 7 system I run as a Standard User (as one should, not as an Administrator), but regardless I have tried running the Arduino application normally and as an Administrator user but it has the same result. And it seems strange that it encounters the same style of error across multiple different operating systems.

Have I just been really unlucky and got a dud for my first Arduino or am I missing something obvious?

Thanks for your time and help.

  • refer to the windows device manager ...... does a comport device appear in the device tree when you plug the arduino into the USB port?
    – jsotola
    Mar 4, 2019 at 21:58
  • 1
    You didn't mention drivers in your troubleshooting - have you installed the USB-chip drivers on your PCs? The clone boards come with a different USB <-> TTL Serial chip or firmware (not sure which) than the Italian boards and require CH340 drivers on the PC side to talk to it. (Whereas many OSes include drivers for the FTDI firmware/protocol used on Italian boards). If not, you can find them on the Downloads section of Elegoo's site.
    – JRobert
    Mar 4, 2019 at 22:05
  • Yes it does, I think you may have missed certain elements of my initial post. I'm very confident with the selection, monitoring and configuration of COM ports. Mar 4, 2019 at 22:05
  • Thanks @JRobert for that insight. I've tried downloading the CH340 drivers from Elegoo's website and installing those but no change. Mar 4, 2019 at 22:23
  • 3
    @JRobert I think you may have just nailed the problem with your CH340 comment - I didn't think it had worked initially after installing, but after a reboot it began to work on my Win7 64 bit system! Thank you. At least this proves to me that the Uno board is not broken and is worth wrestling with on other operating systems if I have to. Thank you everyone for your time and help. Mar 4, 2019 at 22:33

1 Answer 1


On Linux "Permission Denied" generally means one of two things:

  1. You're not in the dialout group (or you haven't logged out and logged in since), or
  2. Something else is using the serial port.

For 1:

sudo usermod -a -G dialout ashley
<log out or reboot>

For 2:

The most common culprit is ModemManager. The simplest cure is to uninstall it:

sudo apt-get remove modemmanager
  • I assume ashley would be your username.
    – Gerben
    Mar 5, 2019 at 14:03
  • 4
    @Gerben No, mine would be matt. Ashley's would be ashley... ;)
    – Majenko
    Mar 5, 2019 at 15:05
  • OP is on Windows. why an answer for Linux?
    – Juraj
    Mar 9, 2019 at 11:52
  • 1
    @Juraj He's on both Windows and Linux. Read the question: "and have just tried it out of the box connected to two different systems; one Windows 7 64bit Enterprise the other Kubuntu." and "On the Linux system I was seeing a similar behavior with slightly different wording: Permission Denied"
    – Majenko
    Mar 9, 2019 at 12:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.