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Old 12-10-2008, 02:07 AM   #1
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Null modem serial connection problem

hi, my setup is 2 linux systems connected by a null modem serial cable.
i tried to follow this guide:

i manage to setup each side to the settings as displayed in the guide without any problems, and without any error messages. however, it doesn't work as input from either terminal doesn't appear on the other end.

i tried to do simple things like "cat /dev/ttyS0" on one side and "echo "asdasd" > /dev/ttyS0" on the other side but it doesn't work as well.

my dmesg | grep ttyS output from one side is :
serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
00:07: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
00:08: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
0000:00:03.3: ttyS2 at I/O 0xec98 (irq = 201) is a 16550A

the other side is similar, just that it has only ttyS0.

on the side with ttyS0 and ttyS1, i tried both S1 and S0, both doesn't work. can somebody please give me some clues on fixing this?

thanks - adrian
Old 12-11-2008, 09:57 AM   #2
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Check that your null modem cable is correct.

In the *nix world, DCD is implemented.
Old 12-11-2008, 10:20 AM   #3
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I would skip the cat echo test and fire up minicom on both computers. Configure the port settings the same and disable hardware flow control. What you type on computer A should be displayed on computer b.


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