Serial ports and USB problems

[95user]

Host OS Ubuntu 11.04 64bit
Guest OS W7 64 bit
VB 4.1.6 including ext pack and guest additions.
I have an app which uses an USB to serial converter (COM 3 assigned). If I enable and set serial port 2 to COM3 W7 device manager shows that COM 4 and CP210x COM3 are working correctly. I haven't enabled COM4!!! Also I can't choose to enable COM1 and COM3 at the same time because they use the same IRQ. I get COM1 and COM4!! I can live with this by using different version where only one serial port is open but HOW DO I get the USB to serial converter to function. I am member of vboxusers. Should the serial port be assigned? CP210x USB to serial converter is filtered. What am I missing being a newbie to VB.
The same USB to serial converter works beautifully in W7. Any ideas anybody?

[mpack]

If the guest OS is picking up the USB device then VirtualBox has done its work. Everything else sounds like questions for whoever sold the USB device to you.

I can tell you that it would not be unusual for a USB-serial dongle to provide two ports. How you would go about enabling/disabling USB serial ports and assigning IRQs is way beyond the scope of these forums. The only serial ports VirtualBox is directly responsible for are the ones described in your VM settings (which should be disabled btw, since they are not relevant when you are using USB).

Speaking of the VMs serial ports, is there some reason why you particularly wanted to use USB? An alternative route would have been to attach the USB device to the host, then map a selected host comm port to the virtual COM1 in the guest.

[95user]

Futher study revealed that host OS need to recognize USB2serial converter. Unfortunately my device version number isn't included in the linux driver file so can't find it. Need to add version number and recompile kernel!