Serial Port Detection

WrightExposure · 12-26-2006, 11:12 PM

Hello all,

I'm sure this has been asked answered several times already but I did a quick search and didn't come up with results that helped. Oh and yes I'm VERY new to linux so all this is new to me so take that as a warning LOL.

How in Fedora Core 5 do I see if it is seeing a serial port? and of course does it have to be mounted to have it continue to be seen by the system.

In the long run I'm attempting to get the digitemp project installed on this computer.

Thank for helping a newb and hope all of you have had and will continue to have a great holiday season so far.

Mark

blackhole54 · 12-27-2006, 12:18 AM

Quote:

Originally Posted by WrightExposure

How in Fedora Core 5 do I see if it is seeing a serial port? and of course does it have to be mounted to have it continue to be seen by the system.

Serial ports are not mounted. They are just there. I do not know what you mean by "seeing" a serial port. If your system has a single serial port built in it is probably known as /dev/ttyS0.

On my system I find the following lines from boot time logged in /var/log/messages

Code:

Dec 25 18:09:25 Vectra kernel: ttyS00 at 0x03f8 (irq = 4) is a 16550A
Dec 25 18:09:25 Vectra kernel: ttyS03 at 0x02e8 (irq = 3) is a 16550A

(Note: I am not running FC -- YMMV; I also don't know why it is listed as ttyS00 -- rather than ttyS0, which, as I noted, is how you refer to it in operation.) The first line is a built in serial port and the second line is my ISA modem. There should be a second built in port, so I must thank you for bringing it to my attention!

( I probably accidently left it disabled after playing around with a different modem card.)

You can "talk" to a serial port using the minicom program. This is a command line program, so you need to use something like gnome-terminal or a virtual terminal (accessed via Ctrl-Alt-F1, Ctrl-Alt-F2, etc). You should read its man page before attempting to use it. You must initially set it up by running the command minicom -s as root. After it is set up, it can be run as a normal user. This is normally used to control a modem, but it might be useful for what you are trying to figure out. Two other commands you might want to look at are setserial and stty.

Without really understanding your question, I hope this has given you something you can work with.

EDIT: I just tried minicom with my "missing" /dev/ttyS1. Apparently minicom does not give you any indication if nothing it there.

WrightExposure · 12-27-2006, 08:09 AM

Hi blackhole54,

What I mean by detecting it is, I don't see anyplace were a serial port is being listed. Being new to this linux stuff I could of course be looking in the wrong place.

The only thing I see in /var/log/messages is were it mentions something about the uarts. Nothing like ttysX (x being a number) is listed.

Anyother ideas?

Mark

WrightExposure · 12-27-2006, 09:28 AM

Actually I think I might have 'found' what I'm looking for.

I think I need to run the makedev command. I know i haven't done and the person that helped me setup the box I don't think did either.

Will report back later tonight on how things went.

Hitboxx · 12-27-2006, 09:33 AM

What about System->Administration->Hardware if you're using Gnome?

blackhole54 · 12-28-2006, 06:04 AM

Quote:

Originally Posted by WrightExposure

I think I need to run the makedev command. I know i haven't done and the person that helped me setup the box I don't think did either.

In the past running makedev would not normally be needed; creation of the /dev entries would be handled at installation. And I believe FC5 uses udev to handle the dev entries, so that makedev would be completely inappropriate since udev creates the /dev entries automatically as devices are detected.

I debated about mentioning udev in my first post but decided it might just make things too complicated at that point. Udev started some where in the 2.6 kernel series (I just spent about 15 minutes unsuccessfully trying to determine at what point). Unfortunately virtually all of my experience is with 2.2 and 2.4 kernels. I do have a several month old version of DSL-N which uses a 2.6.12 kernel. But as best as I can determine it does not use udev.

The info I posted earlier was from a 2.2 kernel. A little while ago I booted the same machine using DSL-N with its 2.6.12 kernel. It isn't configured to create log files, but dmesg output did contain the following:

Code:

Serial: 8250/16550 driver $Revision: 1.90 $ 14 ports, IRQ sharing disabled
ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
ttyS3 at I/O 0x2e8 (irq = 3) is a 16550A

So what did your log file say about uarts?

One thing you can try is running the setserial command as root as shown:

Code:

[root@Vectra jim]# setserial /dev/ttyS0
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4

If it lists a number after "UART:" then it is surely seeing your uart. If it lists "unknown" then you might have trouble. If the entry /dev/ttyS0 does not even exist then you should get a "/dev/ttyS0: No such file or directory" error.

You can also see what you can find out in the GUI that shrikant.odugoudar mentioned. I am not up to date on the GUI interfaces.