The XP usb stack was implemented wrong. WIN7 usb stack was implemented correctly. Get a converter from USconverters.com they will work on either system.
I've had converter (GM something) that did not work with a hub. The converter from usconverter works thru the hub. The prolific drivers are not perfect, there was a version that did not work properly. Delete the inf file , reboot and start over.
I have had much better luck with the FTDI chips/drivers than any others. The correct response from the OS should be that the dongle just changes COM ports when moved around to other ports. I have a StarTech 4 port adapter that has the cool option of keeping the same set of COM ports no matter where the device is in the USB chain. That way my instruments don't get bounced around if Windows decides to re-enumerate the USB devices, like after an update.
Some Windows USB drivers seem to (want to) remember the device's identity and location, based on the topology of the USB tree structure... "the device plugged into port 3 of bus 5 is COM5". A lot of the Prolific-based adapters (and their clones) are not uniquely identified on the bus... they don't have unique serial numbers... and thus the drivers can't remember their COM binding by anything other than port location. If you switch ports, it's seen as a "different device" because it's at a different location... it's no longer COM5 (e.g.).
And, some of these drivers can handle / remember only a single instance of the device. If you switch ports, the "old device" has to be forgotten / de-registered and a new one registered, and (in these drivers) this is done by declaring the driver install "stale" and requiring that the driver be uninstalled and reinstalled.
Not a good programming practice.
From your "COM D" comments, I'd guess that this particular driver is so poorly coded that it can only "remember" or "manage" a device which is connected directly to one of the ports on a root hub. That's a really *poor* programming practice!
The FTDI devices seem to have at least two advantages here:
- The drivers are generally written a lot better.
- The driver doesn't have to try to "remember" a device's identity by its USB tree location. Each FTDI serial adapter has a unique serial number, which is available via the bus, and the driver can bind a specific COM port to a specific device serial number and will re-create the correct binding when you plug in the device, no matter which port you connect it to (and no matter in which order the system's USB hubs happen to enumerate at boot time or when they are powered up).
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
RS232 has settled a lot. Thirty years ago, I had plenty of fun wrestling with RS232 until it worked. These days things are simpler. Nearly everyone ignores the hardware handshake, which simplifies things quite a bit. The PC industry settled DCE vs. DTE issues. Software often figures out the right baud rate, which simplifies things a bit more.
USB is not designed to be universal. It's designed to generate revenue.
Police are looking for a Serial port killer in Houston TX. He's committed 3 killings since the weekend, and is still at large. Please contact the Houston police department or the FBI if you see the guy. He will be armed and is extremely dangerous.