Onboard COM of P5E-V-HDMI

Onboard COM of P5E-V-HDMI

[Russell Shaw]

Hi,

I'm running 2.6.24 on debian/unstable.

I have an Asus P5E-V-HDMI (Intel G35 chipset) with on-board rs232 serial port.

http://www.asus.com/products.aspx?l1=3&l2=11&l3=584&l4=0&model=1929&modelmenu=1


With an LED breakout box connected, i get these signals asserted
when doing: cat random.txt > /dev/ttyS0:

TD   faint green
RD   flickering red and green
RTS  red
DTR  red

When i'm not sending anything i get:

TD  red
RD  green
RTS green
CTS red
DSR red
DCD red
DTR red


IIRC, RD should not be asserted red or green at all because it
should be an input.

My other serial cards behave ok.

I checked the cable between the motherboard and breakout box.

Re: Onboard COM of P5E-V-HDMI

[Chris Gibson]

Could be a fault with the Mother board.  Could be a grounding fault.

First thing that I would check is continuity on the RS232 port ground
pin to the motherboard earth with a multimeter (say one of the black
leads from the power supply).

It's my first guess that the port has a bad ground connection, and that
you are seeing a current flow out of the output signals back through the
input signals down to ground via input pull down resistors on the
motherboard, or in the chip-set.

If you have access to a CRO I would say that it would be worth looking
at the serial port wave forms. 

On Tue, 2008-12-09 at 03:34 +1100, Russell Shaw wrote:
> Hi,
> 
> I'm running 2.6.24 on debian/unstable.
> 
> I have an Asus P5E-V-HDMI (Intel G35 chipset) with on-board rs232 serial port.
> 
> http://www.asus.com/products.aspx?l1=3&l2=11&l3=584&l4=0&model=1929&modelmenu=1
> 
> 
> With an LED breakout box connected, i get these signals asserted
> when doing: cat random.txt > /dev/ttyS0:
> 
> TD   faint green
> RD   flickering red and green
> RTS  red
> DTR  red
> 
> When i'm not sending anything i get:
> 
> TD  red
> RD  green
> RTS green
> CTS red
> DSR red
> DCD red
> DTR red
> 
> 
> IIRC, RD should not be asserted red or green at all because it
> should be an input.
> 
> My other serial cards behave ok.
> 
> I checked the cable between the motherboard and breakout box.
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-serial" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>