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Did you try jumpering the TTY Rx & Tx pins? Your TTY is a real device, and so the Tx & Rx channels carry actual data. If the Rx pin has no signal on it, you shouldn't expect to see any data.
--- rod.
My program get the device ( a simulator)data(text data) from ttyS0.
I am trying to send data(using "cat filename > /dev/ttyS0") from the command line(gnome-terminal) to ttyS0, so that the program can use this data sent through "cat" for testing purpose.
However, this does not work. The program can not get the data and I open the gtkTerm on port ttyS0, which does not have any data displayed either.
I used "echo" in my original post to test out data can be sent to ttyS0 from command line.
Distribution: Ubuntu 11.4,DD-WRT micro plus ssh,lfs-6.6,Fedora 15,Fedora 16
Posts: 3,233
Rep:
well for starters ttySX devices are usually reserved for physical serial ports which means that unless you get a loopback adapter for your serial port then /dev/ttyS0 is useless
Unless your program is written entirely as a shell script, you should read up on serial ports, and the programming of them. Serial HOWTO Serial Programming HOWTO
In the short term though, you can achieve somewhat what you are attempting by simply looping back the Tx pin to the Rx pin on the serial port. On a female connector, all you need is a paper clip or short piece of wire. The relevant conductors are normally pins 2 & 3 on a standard 9-pin or 25-pin serial connector (although the roles are typically reversed between the two formats). If this is a USB <==> serial converter, you must first have a suitable Linux driver to support it.
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