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Windows 7: Cannot access USB serial converter

28 Apr 2010   #1

Win7 Ultimate 64-bit / WinXP Pro 32-bit (dual-boot)
Cannot access USB serial converter

Hi all

I have a USB<->serial converter (several, actually) that I cannot get to work under Windows 7. I know the hardware works.

When I try to open the virtual serial port in a terminal program, I get an error message stating that it cannot open the port. When I try to use the old-fashioned command line method ("copy test.txt com7" from the "DOS prompt"), I get an "Access denied" error message.

Any ideas what the problem can be? I suspect it is some kind of access rights issue. But I need help finding it.

More details:
My computer is a dual-boot Windows 7 Ultimate 64-bit / Windows XP Pro 32-bit system. The USB serial converter worked immediately under WinXP when I rebooted, and it even works in the WinXP virtual machine under Windows 7. I have the latest certified drivers (from FTDI), which are stated to function under Win7 64-bit.

The serial converter appears as it should in the Device manager.

My computer has one physical COM port, and I can access that one without any problems.

The serial converter is a USB-RS485-WE-1800-BT from FTDI. I have tried a USB<->RS232 converter (don't have the model number here), but it behaved exactly like the other one. I also started the terminal program as an adminstrator (since I suspected access rights issues), but it did not help.

I have tried uninstalling the drivers, then installing the latest certified driver and the even later non-certified driver, but still had the same behaviour.

So once again: Any ideas what the problem could be? And more importantly, how do I fix it?

My System SpecsSystem Spec

28 Apr 2010   #2

Win7 Ultimate 64-bit / WinXP Pro 32-bit (dual-boot)

... I can add that I also started the terminal program in XP compatibility mode, with administator's rights, but it behaved as it did before.
My System SpecsSystem Spec
11 May 2010   #3

Win7 Ultimate 64-bit / WinXP Pro 32-bit (dual-boot)

It appeared to be the mobile phone software, that automatically (and unwantedly) polled the COM port, hogging it for other terminal software...
My System SpecsSystem Spec

26 Oct 2012   #4

32 bits

Hi, I have the same problem. My serial port COM7 is not recognised by an application but i can see it in the device manager. And I have admin access..
How did you fix it?

My System SpecsSystem Spec

 Cannot access USB serial converter

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