Fedora Core 5: # cat /dev/ttyS0 error

polemon · 05-14-2007, 04:09 AM

Hi.

I'd like to use the smart-card reader/writer that I have, it connects to a RS-232 Serial port.

the Applications for that device work fine on an old Laptop with such RS-232 port, but not on my desktop computer.

when I try to read that port, I get an error message:

# cat /dev/ttyS0
cat: /dev/ttyS0: Input/output error

I do it as root, and I do have read and write permission.

how do I get rid of that error?

please help,

--polemon

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michaelk · 05-14-2007, 09:05 AM

Quote:

the Applications for that device work fine on an old Laptop with such RS-232 port, but not on my desktop computer.

Can you provide some details? What applications?

Does /dev/ttyS0 exist? Your serial port must be configured with the same settings as the reader/writer.

Try:
cat < /dev/ttyS0

polemon · 05-14-2007, 11:19 AM

Of course it does exist, i get an Input/output error, not an cat: /dev/ttyS5: No such file or directory error.

The application just moves values to the ttyS0 port (i.e writes to it)

Code:

# setserial -a ttyS0
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 auto_irq

those are the exact same setting that i have on my laptop, where the port actually does work.
I can cat that port there. When nothing's connected to it, nothing is displayed, but I don't get an error message...

# cat < /dev/ttyS0
cat: -: Input/output error

What now?

polemon · 05-14-2007, 06:26 PM

Ok, I partially solved the problem:

The problem was, the ports IRQ-setup in BIOS was confusing the Kernel (it was set to auto).
I changes that to IRQ 4 and all is good now.

Almost all, though...

After systemboot, the permissions on /dev/ttyS0 is 660
I'd like it to be 666, is there a config file, that I could set things up with, or should I use setserial in rc.local?

--polemon

samstar · 05-14-2007, 07:37 PM

Hi,

Don't know if you might consider this a security breach, but to get access to my serial GPS, I added my user account to the "uucp" permissions group instead of changing permissions on the device itself.

Sam