Re: [gentoo-user] [OT] laptop desktop serial connection don't work on one direction

[Kfir Lavi]

On Sat, Nov 5, 2011 at 12:17 PM, Mick <michaelkintzios@×××××.com> wrote:

> On Saturday 05 Nov 2011 09:20:19 Kfir Lavi wrote:
> > Hi all,
> > I have a problem connecting my laptop to my server at home with a serial
> > cable.
> > I have cable end for /dev/ttyS0 and 2 cable ends for /dev/ttyUSB0.
> > This lets me test the connection between all serial outputs.
> > Desktop1-minicom <-> Desktop2-minicom
> > works with all connections, i.e ttyUSB0 <-> ttyUSB0, or ttyS0 <-> ttyUSB0
> > and viseversa.
> > So when connecting 2 desktop computers everything works as expected.
> >
> > The problem:
> > When I connect my laptop to any of those desktops, I get just one way
> > connection!
> > If I swap the sides of the cable, the one way connection switch side.
> > The laptop doesn't have ttyS0, so it have to be connected via ttyUSB0
> > When I swap sides, it is just between two usb dongles.
> >
> > The usb dongles are PL2303 both sides.
> > Settings of minicom is 38400 8n1  Hardware Flow Control=OFF
> >
> > Laptop setserial:
> > setserial -a /dev/ttyUSB0
> > /dev/ttyUSB0, Line 0, UART: 16654, Port: 0x0000, IRQ: 0
> >         Baud_base: 460800, close_delay: 0, divisor: 0
> >         closing_wait: infinte
> >         Flags: spd_normal
> >
> > Desktop1 setserial:
> > setserial -a /dev/ttyS0
> > /dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4
> >         Baud_base: 115200, close_delay: 50, divisor: 0
> >         closing_wait: 3000
> >         Flags: spd_normal skip_test
> >
> > setserial -a /dev/ttyUSB0
> > /dev/ttyUSB0, Line 0, UART: 16654, Port: 0x0000, IRQ: 0
> >         Baud_base: 460800, close_delay: 0, divisor: 0
> >         closing_wait: infinte
> >         Flags: spd_normal
> >
> > I tried to add the skip_test but this seems to be not working.
> > I'm not sure what to do next.
> >
> > Any help will be appreciated,
> > Thanks,
> > Kfir
>
> I think that you will need the pin mapping of a 'null modem' to be able to
> have bidirectional connectivity.
>
> Have a look here:
>
> http://en.wikipedia.org/wiki/Null_modem
>
> I think I still have an RS-232 to D9 null modem adaptor somewhere in my
> bins
> of spares.
>
> HTH.
> --
> Regards,
> Mick
>
Hi and thanks for replaying.
This cable setup is working between the 2 desktop computers
bidirectionally. So, it seems that that part I got right.
The problem is when the laptop use the same cable connection and have just
one direction.

Basically, I need to cross pin 2 and 3, and I have the setup open, so I can
cross whatever pin I want.

Regards,
Kfir