We have been using this RS232 USB hub here: Serial Gear

It is required for a POS application, since the PC requires many COM ports.

Our problem is the linked hub is absolutely terrible. It has driver issues, gives BSOD, and if you unplug and plug it back it the ports get renumbered almost randomly.

Our programmers also complain of having to restart windows when the application changes the baud rate, etc.

Does anyone know of a good USB->RS232 solution that doesn't suffer from these issues?

We are running Windows XP SP3, and need anywhere from 4-8 ports.

UPDATE: We found a newer driver on SerialGear's website. We are going to try that out, but also look into some of your links, guys.


Rather than using USB to RS232 adapters, have you considered installing an internal multi-port RS232 card (or more if required)? The reason you're having trouble is due to Windows' rather less than perfect handling of USB which, to put it mildly, keeps life interesting. By eliminating the USB portion you will have far fewer problems and much more predictable and consistent behaviour. As it's been a few years since I've used such a card I can't recommend any in particular.

  • I use PCI cards with 2 serial ports on each. I've tried half a dozen USB ones and most are not fully implemented or just don't work right. I think one from SIIG worked the best, but the cards seem way better. I've only used the 2 port models, but you could try two of these siig.com/ViewProduct.aspx?pn=JJ-E40011-S3. – Bratch Nov 1 '09 at 5:51
  • I don't know if they're still available but in the past I've seen cards with as many as eight RS232 ports. – John Gardeniers Nov 1 '09 at 8:22

I don't know if they'll work for your application (you may need to check the specs in detail) buy you can get single USB->serial adaptors - I've been running a fax/modem off a cheap one for about two years.

Something like this (I have no affiliation with that product or supplier, in fact I've never hear of them, it is just the first I clicked of the many that came up in a Google "shopping" search for "usb serial"). You could get one to test it works to your product's satisfaction, and if it does get a pile of them and some USB hubs.

Not nearly as tidy a solution as 8 ports on one USB device though!

  • Looked into this, but I think our USB ports would be maxed out. It seems like we need a 4 or 8 RS232 to 1 USB port. – jonathanpeppers Oct 8 '09 at 16:35
  • You can hook up to 127 devices to each USB controller, so as long as you use powered hubs the USB arrangement shouldn't limit you (though the quality of the USB->Serial ports, and the practicalities of having many cables floating around, may). – David Spillett Oct 8 '09 at 19:23

Have you looked at Digi? They were pretty popular back in the BBS days. Lantronix might have a solution as well, but they seem to be focused on serial over networking.


I've seen the SeaLevel SeaLink USB<->RS232 adaptors used with decent success.

http://www.sealevel.com/product_detail.asp?product_id=528&USB_to_RS_232_Serial_Interface_Adapter_ would be similar to what you posted.

I have heard the ports get renumbered at times, though. Not sure if that problem is endemic with USB Serial converters or what.

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