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<TITLE>The Answer Guy 48: Setting COM port speeds</TITLE>
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<H4>"The Linux Gazette...<I>making Linux just a little more fun!</I>"</H4>
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<H4>By James T. Dennis,
<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a><BR>
LinuxCare,
<A HREF="http://www.linuxcare.com/">http://www.linuxcare.com/</A>
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<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Setting COM port speeds</H3>
<p><strong>From Jason_Magill on Thu, 23 Sep 1999
</strong></p>
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Setting COM port speeds
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<P><STRONG>
Answer Guy,
</STRONG></P>
<P><STRONG>
I have an application that I am running that requires me to read the
serial port (Com2). The problem is that I need to read it at 9600
7-E-1. How would you go about doing that so when the system is
rebooted it will automatically read the serial port at 9600 7-E-1?
</STRONG></P>
<P><STRONG>
I could really use your help.
</STRONG></P>
<P><STRONG>
Thanks,
Jason
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
You should be able to do that with the following command:
</BLOCKQUOTE>
<blockquote><pre> stty 9600 parenb cs7 &lt; /dev/ttyS1
</pre></blockquote>
<BLOCKQUOTE>
... or something like that.
</BLOCKQUOTE>
<BLOCKQUOTE>
Note you must redirect <EM>INPUT</EM> from the serial port to the
'stty' command. This is because the terminal settings are
accomplished through an<TT> ioctl()</TT>.
</BLOCKQUOTE>
<BLOCKQUOTE>
You might also look at the 'setserial' program. It
works a bit differently (and is Linux specific) whereas the
'stty' program has been around for UNIX for many years.
</BLOCKQUOTE>
<BLOCKQUOTE>
Note also that we use ttyS1 for MS-DOS COM2. This is
because Linux counts these devices from zero. There is no
guarantee that Linux will detect these ports in the same
order as MS-DOS, but usually COM2 should be <TT>/dev/ttyS1.</TT>
</BLOCKQUOTE>
<BLOCKQUOTE>
The parenb is to set "parity even" (I don't know why the
have the "b" there --- for "byte" maybe?) and the cs7 is
to set the "character size." There are many other 'stty'
settings available. Read the 'man' page for details.
</BLOCKQUOTE>
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<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
>Copyright &copy;</a> 1999, James T. Dennis
<BR>Published in <I>The Linux Gazette</I> Issue 48 December 1999</H5>
<H6 ALIGN="center">HTML transformation by
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Starshine Technical Services,
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