[CentOS] Need to test serial port connection

[fred smith]

On Fri, Feb 27, 2009 at 10:18:34AM -0500, William L. Maltby wrote:
> 
> 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.

And some of t hose boards have a set of pins/header on the board and a little
"slot fillter" thingy with a 9 pin serial socket on it and a small ribbon cable 
to plug into that header, which will then provide access to the second serial
port. I've seen a lot of ASUS boards like that. wouldn't surpirse me if other
vendors to it, too. probably saves board design complexity and maybe a few
hundredths of a penny per board. :)

-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
  "And he will be called Wonderful Counselor, Mighty God, Everlasting Father,
  Prince of Peace. Of the increase of his government there will be no end. He 
 will reign on David's throne and over his kingdom, establishing and upholding
      it with justice and righteousness from that time on and forever."
------------------------------- Isaiah 9:7 (niv) ------------------------------
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <http://lists.centos.org/pipermail/centos/attachments/20090227/b4e40a66/attachment.sig>