Serial port

just.srad · 08-20-2009, 09:34 PM

I have just discovered that by changing the I/O address of the Port in BIOS setting , we are actually change the COM1 point to another chip.

Intial I/O address After change the I/O address

COM1 : 3F8 COM1: 2F8
COM2 : 2F8 COM2: 3F8

If COM1 is faulty, and we would like to use COM2 , so i change it to COM2: 3F8. I do it this way, because the software apps is hard-coded to look for the COM1 at the address 3F8.

In linux point of view, /dev/ttyS0 and /dev/ttyS1 will still point to the same I/O address before and after i changed the BIOS setting.

My question is , if i have a multi-port card, how do i use linux to choose the physical COM port since it i cannot change it like i change for COM1 and COM2 in BIOS setting.

Thanks in advance for valuable advise.

Justin

GrapefruiTgirl · 08-20-2009, 10:39 PM

See if your OS has a file called /etc/serial.conf which is where on my system (Slackware) I can program which serial port is which, as well as other options for the serial ports. I do have a 2-port multi-card installed, plus one onboard serial port, and I can program each of them in that file..

NOTE: If you are having this trouble on a Mac, I'm not sure how this applies, as I'm not familiar. If it's not a Mac, (and in the future) please tell us what machine & OS you are using.

Here's what I see in dmesg during boot, as well as what I have in my serial.conf file:

Code:

dmesg output during boot for my multi-card (Quatech 2-port PCI card):

0000:05:08.0: ttyS0 at I/O 0xe880 (irq = 19) is a 16550A
0000:05:08.0: ttyS1 at I/O 0xe888 (irq = 19) is a 16550A

And here's what's in my serial.conf file (I'm not currently using the on-board serial port so it's commented out):

# onboard:
#/dev/ttyS0 uart 16550A port 0x3F8 irq 4

# PCI 2-port card
/dev/ttyS0 uart 16550A port 0xe880 irq 19
/dev/ttyS1 uart 16550A port 0xe888 irq 19

Sasha

just.srad · 08-22-2009, 05:44 AM

Thanks GrapefruiTgirl,

I will use your notes as my guide to further explore on the I/O cards
that our company is using..

As i am a technical support guy for the POS machine, and quite frequent certain port is down, and hence i am trying to find a way to fix a particular device to another com port.

Thanks for your reply and appreciate it. =)

Justin

IanVaughan · 11-27-2009, 07:22 AM

Running with RHEL 2.6.18-128.el5 #1 SMP
I have no serial.conf

Any other ideas?

I am trying to use a Serial card fitter via a PMC!