Access to COM port is denied

After upgrading from 1.3.48 to 1.3.49, now getting the above error.

What would be the cause? New computer, nothing plugged into USB, a frustrating error.


Neil, this error typically occurs when the port is already opened by an application.

I know it sounds far fetched, but can you check that you don’t have two instances of Mission Planner running (with possibly a previous one not visible on screen), or any other program running in the background that would have accessed that port (with task manager)? Does this happen again with a full reboot and a new Pixhawk connected by USB after?


There is only the one com port opened and attached. Rebooted everything, multiple times, no luck. There were other USB drivers that had been recently installed, which were being removed one at a time. Eventually, ended up rolling all the way back to original installed image. Problem solved.

Pretty much a BS issue though. Seems like there should be a method to determine WHAT driver is causing the conflict, and then kill that specific driver. Not a programmer though, and not about to attempt to install a debugger and chase that rat down that hole.

Better solution would be to run VM’s for specific software uses, which is easy enough to do, being this app appears to be susceptible to breakages.

Thanks for the suggestions.