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

[Mick <michaelkintzios@gmail.com>]

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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

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