One of my upcoming assignments is to get and configure a workstation that requires 5 or 6 DB9 serial ports for certain peripherals.

USB stuff is obviously easy to expand as most USB hubs will autodetect dozens and dozens of different USB ports and their attached devices, but the last time I setup a system with a bunch of serial ports, I had a helluva time getting all the IRQ, COM#, etc configured correctly.

Since USB and firewire have replaced a lot of the inputs, have their been any reliable serial port expansions developed lately? I'm aware of some of the 2xDB9 PCI expansion cards you can get but like I said, I had a lot of issues avoiding address conflicts. Can anyone recommend something reliable? I imagine I can easily get a system with 2 serials included so I'd need to add about 4. Thanks.

1/30/2008 4:20:21 PM

This is kind of pricey but it might be worth it if it works. I haven't used it before.

http://www.flexport.com/usb_to_serial_hub.html

But I have used a similar product to this:

http://www.lantronix.com/device-networking/external-device-servers/mss4.html

from the same company that was single Serial -> Ethernet. Those things were like $80 a pop though so I imagine the 4 port is expensive.

1/30/2008 4:57:14 PM

the main problem here is how the serial interface is handled in windows

no matter what interface you use to physically connect the serial interface to the computer, you're still going to have IRQ problems, as an IRQ has to be allocated to each serial port regardless of whether it's on the PCI bus or the USB bus.

1/30/2008 5:03:31 PM

^^thanks for the links, i'll investigate

^yeah but does XP SP2 have any updates or fixes that helps that out? IIRC the last time I setup a system with this many DB9s it was probably a WinNT4.0 system. I'd imagine XP would have better support but I don't know how much better

1/30/2008 5:15:50 PM

nah, that's how the BIOS allocates resources for I/O ports

serial ports are just that way... that's how they've always been.

it'll take some work, but you should be able to get it working, i have a system up right now at work with 15 serial ports.

if you start getting IRQ conflicts, go into the bios and disable stuff you're not using (parallel port, onboard sound, etc.)

1/30/2008 5:25:37 PM

ok well shit thats kind of what i did last time...if you got 15 working i can definitely get 6 working although that first link that DiryMonkey posted looks like i could get the same results with a little less work

1/30/2008 5:27:15 PM

figured i'd give you guys an update

I ended up getting a StarTech 4-port serial card...basically its a PCI card that has two serial ports...the card itself has two ribbon cable "jacks"...the 2nd part of the card is a filler panel (doesnt actually plug into PCI) with 2 more 9-pin serials, but each has a ribbon cable going to the jacks on the original card

so 2 card slots are required (only 1 PCI bus though)

i downloaded an updated (WinXP) driver off their website and installed...bam...click yes, install, etc four different times for all 4 ports but after that everything works fine...I have my built-in serial (COM1) that came from the factory...then I have COM3, COM4, COM5, COM6 which have all been verified and work

long story short, adding a number of aftermarket serial ports to a computer is a LOT easier than it used to be...I didn't have to go into BIOS, didnt have to mess with IRQ settings, etc

2/26/2008 4:45:28 PM