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I have a laptop which has only one serial port.

I went into:


directory, and I found:


How do I know which of those "ttyS" refers to my serial port?

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3 Answers 3

up vote 4 down vote accepted

I think it's this command:

dmesg | grep tty

Running that on my own Linux box (which only has 1 Serial port) produces a single ttyS0 output line. Try it on your own, you will see what I mean.

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ttyS0 through 3 correspond to COM1 through 4, respectively. They usually have the same hardware resources and are not always detectable, so they always exist.

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thanks for the answer. So say I want to tell Linux that I want ttyS0 to map to my serial port hardware, what do I need to do? –  ShaChris23 Apr 14 '10 at 21:18
You would use setserial to map the resources ttyS0 uses to that of your serial port. linux.die.net/man/8/setserial This isn't normally required though, since anything beyond COM4 usually has enough auxiliary hardware to allow Linux to detect it and add a serial device as appropriate. –  Ignacio Vazquez-Abrams Apr 14 '10 at 21:26

If you need to do this programmatically reading the output from dmesg can be troublesome, instead the folder /dev/serial/by-id has sym links that are named after identifiable data of your device and point to the specific /dev/tty* they are connected to.

I'm not sure if this is some special udev rule that is distribution specific, but it works well in Ubuntu, let me know if it works.

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