[CentOS] Need to test serial port connection

William L. Maltby CentOS4Bill at triad.rr.com
Fri Feb 27 15:18:34 UTC 2009


On Fri, 2009-02-27 at 14:51 +0000, Anne Wilson wrote:
> On Thursday 26 February 2009 13:37:00 William L. Maltby wrote:
> > > Feb 26 12:12:25 borg2 kernel: serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is
> > > a 16550A
> > > Feb 26 12:12:25 borg2 kernel: serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is
> > > a 16550A
> >
> > Didn't you say there was only one port? There might be a second on the
> > main board that is accessible via a header. If it's not hooked up
> > disable all but the first in the BIOS (later). It's not really hurting
> > anything as is, but it will free the I/O address and IRQ for assignment
> > to other devices. But wait until you have things working - I suspect you
> > have _two_ ports (probably 1 9 pin and 1 25 pin). A second port of 25
> > pins might easily be mistaken for a printer port. Long ago a switch from
> > Centronics style to RS-232 style began to become the "standard".
> > Physically, it looks the same as a serial port, the visual difference
> > being the "gender" of the connector will be opposite.
> 
> Just to update you on this.  I checked the motherboard manual, and it clearly 
> says there is one serial port and one parallel port.  Strange that 
> /var/log/messages seemed to report two, isn't it?

Ummm .... maybe. In my experience docs are often not updated when a
minor design change is made to hardware. But there is another
possibility ...

What chip set on the mobo? Many chip sets include dual 16550A support
and the mobo manufacturer, to save a penny or two or space or ease
circuit trace design, might only provide a pin-out for a single port.

A review of the chip set specifications might confirm this. Then a
visual inspection of the mobo, or a look at the layout in the manual (if
you can rely on that at all) might confirm.

Hardly seems worthwhile unless you foresee a need for a second serial
port in the future.

> 
> Anne
> <snip sig stuff>

-- 
Bill




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