Skip to content


Subversion checkout URL

You can clone with
Download ZIP
Tree: a8cd90f850
Fetching contributors…

Cannot retrieve contributors at this time

127 lines (99 sloc) 4.99 KB
Thu Jan 18 15:59:35 MST 2001 removed jcl references for rxtx 1.5 Trent.
The Following was contributed by Vaibhav Andleigh in hopes
that it will make getting started easier for people new to commAPI.
Feel free to contribute additional information in the same spirit.
Hi Trent,
I recently installed javax.comm and RxTx on a few systems and had to write
a very detailed HOWTO on read/writing to your com ports on linux for
beginners. BTW, RxTx is a great tool! In any case, I've included the
HOWTO with this email for the reference of other users. Feel free to post
To get serial port stuff running:
Serial Connection without Java
First, let's setup the serial connection without java and test it.
Connect your computer to another computer/device via a null modem serial
cable. Be sure the other computer/device has software (i.e., minicom)
to receive the signal. For the purpose of these instructions, I'll
assume you have a computer at each end, and will use minicom to
perform the connection testing.
In the case of minicom (on the receiving machine), you'll probably have
to run it as root (since the serial port is owned by root for security
purposes). It's not a good idea to change these permissions. If this
is the first time minicom is being run, you'll have to configure it
first. To do this, ssh to root (not su, anywhere in these instructions)
and type 'minicom -s' without the quotes. Arrow to option 3 and change
the serial configuration device to '/dev/ttyS0' without the quotes.
Exit minicom. Then go and run minicom by typing 'minicom -m -c on'
without the quotes. Assuming you're running minicom on both machines,
run a quick test of the serial connection. Type Alt-Z (or whatever
key-combo gives you help on special keys) and select "Local Echo"(E).
Now type text on both minicom screens and see that the text is going
back and forth.
Java.comm and RxTx installation
First install javax.comm api following Sun's instructions
Be sure to follow the instructions about placing the comm.jar
in the correct directories. You can ignore the details of
the files since it'll be replaced by RxTx
Then install rxtx-1.4-4 following instructions given in
their install page. They have a really useful bit of info
in the INSTALL file talking about where the comm.jar, files(and its contents) are supposed to go
(and what other files ( and
have been created and where). Verify this happened properly.
Assuming you're using jdk-1.2, you can ignore the CLASSPATH
stuff in their extra directions. If you still have problems, they
have a really useful COMMON PROBLEMS section further down in the
Running Trial Applications
We'll test two apps: BlackBox and the Simple demos. These are
included in your .../java/commapi/samples directory. Go to
.../java/commapi/samples/BlackBox/ and type javac *.java to compile
all the classes.
Then create a run shell script as follows (substitute your own relative
java location if necessary):
/usr/local/java/bin/java -classpath
Run this script as ROOT using ssh, not su!
[or make sure permissions for the device files allow the user/group to read
them. See also: lockfiles in INSTALL]
It should put up a screen with a GUI of everything going on for each
of your serial ports. At the top of the screen, you can set the baud
rate. Unless you changed the settings on minicom, it should be expecting
38400 so select that. Go ahead and type in the first left text window
and you should see the text appear in the receiving minicom window.
If you choose to run the apps labeled as "Simple", go to the
.../java/commapi/samples/Simple/ directory and edit the
and files. Convert the /dev/tty/a to /dev/ttyS0 in both
files. Compile both files using javac *.java . Use a run script very
similar to that above (deleting the path reference to BlackBox.jar and
replacing BlackBox with SimpleRead/SimpleWrite as appropriate).
Set up minicom on the other machine and go ahead and run the script.
It should all work. I've attached the run scripts I used for both
programs below:
/usr/local/java/bin/java -classpath
/usr/local/java/bin/java -classpath
Vaibhav Andleigh
Ph.D. Student, Dept. Mat. Sci. & Engr
MIT Room 13-5142 Ph: 617-258-8847
Cambridge, MA Fax: 530-348-8219
"Every man dies, not every man really lives."
--William Wallace, Braveheart
Jump to Line
Something went wrong with that request. Please try again.