We are having difficulty in gettin certain RF modems (mfgrs.= Enfora & Data Radio) to work through the USB port on our docking device. These same modem work well on standard DB9 serial connection in the same docking device. We are told the above style modem requires a IRQ--so the "plug & play" feature of USB is against us.
We are looking into a variety of devices (serial to USB) that suggest they can connect modems without the requirements of a IRQ.
We have had a USB hub designed by a EE Board house that is part of our docking system.
The docking system (ports out) 2 conventional RS232 serials, parallelport , PS-2 & USB+++daughter board that is USB hub ---- converted---- to 'legacy' RS232 serial ports for police market.(more info on request)
Our docking system is a electo/mechanical device that allows certain computers (Panasonic "Toughbook") to be "plugged in" ----docked---- seamlessly ----i.e. police vehicles & utility vans.
The USB hub works well with most devices such as GPS, USB mouse, Modems manufactured by Motorola & Sierra.