PlatformIO IDE on Windows 10: COM4": Access is denied


I’ve just done a clean install of PlatformIO IDE on windows 10 (just to test, I use Linux my dev machines). Install seems to have gone well, I can open and compile projects within the IDE.

However when I get Access is denied errro when I try and upload. I know how to fix permission errors like this on Linux but I don’t know where to start on windows 10! I’ve tried restarting the machine and several different Arduino boards. I’ve made sure the serial window is closed.

There is also a slight error that the port auto detect does not work unless I run list-serial ports first.

avrdude: ser_open(): can't open device "\\.\COM4": Access is denied.
avrdude done.  Thank you.
scons: *** [upload] Error 1
 [ ERROR ] Took 19.26 seconds

Running IDE V1.4.0, CLI V2.11.2


Is there a chance that another process already has the port open?


I had the exact same problem. I solved it by changing the USB-port.