Serial Port Bug?

Tod Merley todbot88 at
Wed Nov 28 10:38:07 UTC 2007

On Nov 27, 2007 7:48 AM, Karl Larsen <k5di at> wrote:
>     I have a software I like to use called gmfsk which uses the serial
> port to turn on and off the transmitter in my radio. It worked fine on
> my old computer. Now when I try to run gmfsk it puts up an error panel
> that says "Not a serial or parallel port". This made me think the new
> computer which has a serial port that is not working.
>     With a volt meter I find some pins have a constant -10.7 volts on
> them which is the standard RS-232 for a no-data signal. In this static
> measure the voltmeter sees no positive volts near +12 volts.
>     Wanting a way to test the serial port I recalled minicom and after
> getting it set up on /dev/ttyS0 it seems happy with Com 1. The old
> /dev/modem is gone on F7. But now what is a way to drive the serial port
> pins to a constant plus voltage with minicom?
>     I have a scope that I can use if there are no way to make a constant
> positive voltage. My fear is that the serial port is broken and can't
> make a positive voltage.
> --
>         Karl F. Larsen, AKA K5DI
>         Linux User
>         #450462
> --
> fedora-list mailing list
> fedora-list at
> To unsubscribe:

Hi Karl F. Larsen!

What I like to do with dmesg is #dmesg > dmesg.txt and then call - say
Abiword to actually paw through the file.  Searching in Abiword for
"serial" I found these three lines together:

Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled
pnp: Device 00:0c activated.
00:0c: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

Looking a bit at the SW you like to use I see that it uses hamlib to
control the rig.  The error message may well indicate that the hamlib
you have compiled talks to a port whose SW interface (e.g. - at I/O
0x3f8 (irq = 4)) ls located elseware..

That is my guess.

Good Hunting!


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