PCI Multiport Serial Cards

[Greg Martin]

Hi all,

Have tried three different brands in two different XP machines, and have
the same problem on all.

Problem is:
PCI cards install fine, and appear to be correct in DevMgr.
Using Hyperterminal, connect from onboard com port (COM1) to PCI serial
card com port (COM3 or COM4) using a crossed serial cable.
Transmit from COM1 to COM3/4 works just fine. Characters received.
Transmit from COM3/4 to COM1, and we get no characters.

Have tried swapping the cable around, and same result.
Have tried installing Win2k, and it works in both directions!!

I'm really stuck on this one. It appears to be caused by WinXP, because:
1. It works under Win2k.
2. All three different brand PCI serial cards have the same problem.
3. Same problem exists on DELL Dimension PC, and Commell PC board.

Greg

 

[Opa]

I am using multiport serial adapters for numerical controlled machines and
experienced never any problem. Did you configure the adapter to start
numbering the additional ports at COM5. COM1 thru 4 are reserved for the
operating system, so don't overlay unless you disabled them in the BIOS. Use
a second PC and a cross cable to test and verify, or use a RS232 loopback
test plug. See: http://www.lammertbies.nl/comm/cable/nl_RS-232.html and
switch to English.

 

[Greg Martin]

I've tried using a second PC, with the same results. The PCI serial
cards receive, but do not transmit characters.

There is no overlay in the BIOS. These is a PCI PNP card, which uses
system-allocated resources.

Using a loop-back plug, of course I get no result, as the TX is not
working (nothing sent on the cable, so no RX).

Once again I state, the cards run fine under 2000/98, etc, but not XP or
2k3. This can only lead me to believe that it is a driver or XP/2003
problem. With the 3 different brands all producing the same results, I
am left with the overriding impression that XP is at fault here...

Greg

 

[Si Ballenger]

Hi all,

Have tried three different brands in two different XP machines, and have
the same problem on all.

Problem is:
PCI cards install fine, and appear to be correct in DevMgr.
Using Hyperterminal, connect from onboard com port (COM1) to PCI serial
card com port (COM3 or COM4) using a crossed serial cable.
Transmit from COM1 to COM3/4 works just fine. Characters received.
Transmit from COM3/4 to COM1, and we get no characters.

Have tried swapping the cable around, and same result.
Have tried installing Win2k, and it works in both directions!!

I'm really stuck on this one. It appears to be caused by WinXP, because:
1. It works under Win2k.
2. All three different brand PCI serial cards have the same problem.
3. Same problem exists on DELL Dimension PC, and Commell PC board.

Greg

You may want to change the card's assigned com port to something
like 5 in the advanced section of its comport setup and see if
that works. Hardware wise, I think com1/3 and 2/4 use the same
interrupts. I think most pci serial port cards have drivers to
use interrupt 9. For another test using hyperterminal to receive
via the null modem cable on com port 1, try the below batch file
and see if it will transmitt the characters out of com 3 and 4 to
hyperterminal on com1.

@echo off
echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaa > com3
pause
echo bbbbbbbbbbbbbbbbbbbbbbbbbbbbb > com4

 

[Greg Martin]

sigh.

This is Windows XP! It is a PNP operating system, and the com ports are
assigned names by Windows. This means that com3 and 4 are Windows com 3
and 4 not BIOS com 3 and 4. (Plus I've tried com 5 and 6 for the devices).

Also, the card is assigned an IRQ by the PCI arbitrator, not by the pci
cards designers. This means it can effectively use any IRQ that the
systems assigns it.

Also... The card is receiving characters. This means that the IRQ and
base addresses are being used by the card to receive the device driver
to retrieve the data being received.

So I'm still back to square 1.

Greg